Method for preparing single-walled carbon nanotubes

Abstract

The present invention relates to the production of carbon materials (eg, carbon nanomaterials) comprising single-walled carbon nanotubes (SWCNTs) and to the carbon materials themselves.

Description

[Technical Field]

[0001] The present invention relates to the production of carbon materials (eg, carbon nanomaterials) comprising single-walled carbon nanotubes (SWCNTs), and to the carbon materials themselves. [Background technology]

[0002] The potential of SWCNTs to fulfill their promise in next-generation transistors and sensors has been hindered by a lack of control over their chirality. Chirality control has been achieved on a laboratory scale by wet selective purification, which inevitably damages the pristine SWCNTs. For this reason, direct chemical vapor deposition (CVD) is the preferred fabrication method. However, even after decades of research, the direct growth of SWCNTs with a narrow chirality distribution remains challenging.

[0003] It is widely accepted that the structure and morphology of catalyst particles during CVD play a crucial role in the properties of CNTs. For example, the Ostwald ripening and flexible morphology of conventional liquid-state catalysts (such as iron, cobalt, and nickel) mean that direct control of chirality remains elusive. Alternatively, catalysts that persist in the solid state during growth maintain hope for in situ chirality control. It has been suggested that the higher energy barrier for incorporating new carbon atoms in solid catalysts could be exploited as a control strategy (see Artyukhov, VI, Penev, ES & Yakobson, BI. Why nanotubes grow chiral. Nat. Commun. 5, 4892, doi:10.1038 / ncomms5892).

[0004] Another long-standing goal is a method for producing small, precisely controlled nanoparticles on a large scale. Because there is a correlation between SWCNT diameter and catalyst diameter, chirality control can be directly linked to the facile fabrication of solid catalysts with narrow size distributions. Recent methods for producing solid catalysts have used either molecular clusters with fixed metal ratios (see Yang, F. et al. Chirality-specific growth of single-walled carbon nanotubes on solid alloy catalysts. Nature 510, 522, doi:10.1038 / nature13434) or special substrate reaction constraints (see Zhang, S. et al. Arrays of horizontal carbon nanotubes of controlled chirality grown using designed catalysts. Nature advance online publication, doi:10.1038 / nature21051). A scaled-up method without substrate constraints would be a great advantage for the industrialization of chirality-controlled SWCNT production. Summary of the Invention

[0005] The present invention seeks to improve the continuous or semi-continuous production of single-walled carbon nanotubes (SWCNTs) by using refractory metal nanoparticles prepared with nearly monodisperse sizes from a continuous gas-phase (aerosol) process. In particular, the monodisperse metal nanoparticles can be fed into a reactor or deposited onto a substrate and used to successfully grow SWCNTs aligned with random or narrowly controlled chirality.

[0006] Viewed from a first aspect, the present invention therefore provides a method for producing a carbon material comprising SWCNTs, the method comprising: (a) generating a stream of refractory metal material suspended in a carrier gas; (b) introducing a stream of refractory metal material into a temperature-controlled flow-through furnace; (c) subjecting the stream of refractory metal material to a temperature sufficient to produce a stream of refractory metal material, wherein the stream of refractory metal material is exposed to a first temperature zone sufficient to vaporize the refractory metal material and a second temperature zone downstream of the first temperature zone, wherein the second temperature zone is sufficient to renucleate the refractory metal material to produce a stream of nanoparticulate refractory metal material; (d) separating from the stream of nanoparticle refractory metal material a discrete stream of nanoparticle refractory metal material exhibiting a selective distribution of nanoparticle sizes; (e) introducing a discrete stream of nanoparticulate refractory metal material into a temperature-controlled reactor; (f) optionally, discharging a stream of reducing agent into a temperature-controlled reactor, wherein the stream of reducing agent and the discrete stream of nanoparticle refractory metal material are exposed to a third temperature zone sufficient to produce a stream of nanoparticle refractory metal; (g) discharging a stream of carbon source into a temperature-controlled reactor; (h) exposing the nanoparticle refractory metal and the carbon source to a fourth temperature zone sufficient to produce a carbon material comprising SWCNTs that can be adapted into a supported or self-supporting form within the temperature-controlled reactor or collected from the temperature-controlled reactor.

[0007] The (or each) stream may be an aerosol stream.

[0008] The refractory metal material may be suspended in the carrier gas as solid particles, preferably solid nanoparticles. The refractory metal material may be formed into a powder dispersion.

[0009] The refractory metal material can be an elemental refractory metal (eg, an elemental refractory metal powder) or a refractory metal compound.

[0010] The refractory metal compound may be a refractory metal complex, salt or organometallic.

[0011] The carrier gas is typically one or more of nitrogen, argon, helium, or hydrogen. Preferably, the carrier gas is nitrogen.

[0012] Preferably, step (a) comprises: (a') spraying a liquid formulation of refractory metal compounds.

[0013] The liquid formulation may be a slurry. The liquid formulation may be an aqueous formulation. The liquid formulation may be a solution, dispersion or suspension. Step (a') may be carried out in a nebulizer.

[0014] In a preferred embodiment, the liquid formulation of the refractory metal compound is a refractory metal salt solution. Particularly preferably, the refractory metal salt solution is very dilute. The use of a very dilute refractory metal salt solution allows for easy and precise control of the particle size of the nanoparticulate refractory metal material exiting the temperature-controlled flow-through furnace.

[0015] The concentration of the refractory metal salt solution may be 1.0 mM or less (in terms of metal atoms), preferably 0.7 mM or less, and particularly preferably 0.3 mM or less.

[0016] Preferably, step (a) comprises: (a'') drying the stream of refractory metal compounds.

[0017] Step (a'') may be carried out by a desiccant dryer.

[0018] Steps (a') and (a'') may be carried out together by spray drying.

[0019] Step (a) may be carried out using a hot wire.

[0020] Preferably, step (a) comprises: (a1) dispersing a stream of refractory metal material in a carrier gas.

[0021] Step (a1) may be carried out in a fluidized bed feeder, a jet mill or a displacement feeder.

[0022] The refractory metal material may be a refractory metal element.

[0023] Preferably, the refractory metal material is a refractory metal oxide.

[0024] Preferably, step (f) is discharging the stream of reducing agent into a temperature-controlled reactor, wherein the stream of reducing agent and the discrete stream of nanoparticulate refractory metal material are exposed to a third temperature zone sufficient to produce a stream of nanoparticulate refractory metal.

[0025] The reducing agent can be hydrogen.

[0026] The carbon material may comprise multi-walled carbon nanotubes (e.g., double-walled carbon nanotubes). Typically, the carbon material is primarily SWCNTs. The SWCNTs may be highly purified SWCNTs. The number of SWCNTs in the carbon nanotube is typically greater than 50%. Preferably, the number of SWCNTs in the carbon nanotube structure is greater than 80%, particularly preferably greater than 90%, and more preferably greater than 95 wt%.

[0027] Preferably, in a carbon material comprising SWCNTs, one or more pairs of chiral indices selected from the group consisting of (2n±2,n), (2n±1,n), and (2n,n) are exhibited by the majority of the SWCNTs. Particularly preferably, in a carbon material comprising SWCNTs, the pair of chiral indices exhibited by the majority of the SWCNTs is (2n,n).

[0028] Typically, the pair of chiral indices is determined by Raman spectroscopy performed on carbon materials in the radial breathing mode region.

[0029] Preferably, n is an integer in the range of 4 to 7, and particularly preferably an integer in the range of 5 to 7.

[0030] The pair of chiral indices can be (12,6), (10,5), (8,4), (12,5) or (9,4).

[0031] Preferably, the pair of chiral indices is (12,6) and / or (10,5).

[0032] Preferably, the pair of chiral indices is (12,6).

[0033] Preferably, one or more pairs of chiral indices selected from the group consisting of (2n±2,n), (2n±1,n) and (2n,n) are exhibited by 50 wt% or more of the SWCNTs, particularly preferably 60 wt% or more of the SWCNTs, more preferably 75 wt% or more of the SWCNTs, even more preferably 85 wt% or more of the SWCNTs, and particularly preferably 90 wt% or more of the SWCNTs.

[0034] Preferably, in a carbon material comprising SWCNTs, a chiral angle in the range of 12 to 26° (preferably 13 to 24°, particularly preferably 16 to 22°, more preferably 17 to 21°, and even more preferably 18 to 20°) is exhibited by the majority of the SWCNTs.

[0035] Preferably, the chiral angle in the range of 12 to 26° is exhibited by 50 wt% or more of the SWCNTs, particularly preferably 60 wt% or more of the SWCNTs, more preferably 75 wt% or more of the SWCNTs, even more preferably 85 wt% or more of the SWCNTs, and particularly preferably 90 wt% or more of the SWCNTs.

[0036] Preferably, in the carbon material including SWCNTs, the average chiral angle of the SWCNTs is in the range of 18 to 20°.

[0037] The melting point of the refractory metal can exceed 2500°C.

[0038] The refractory metal may be one or more of the group consisting of W, Mo, Re, V, Nb, Ir, Ru, Os, and Rh.

[0039] Preferably, the refractory metal is W, Mo or Re. Particularly preferably, the refractory metal is W. Particularly preferably, the refractory metal is Mo. Particularly preferably, the refractory metal is Re.

[0040] In step (h), the nanoparticulate refractory metal may act as a catalyst in its elemental form, or alternatively, the nanoparticulate refractory metal may react with carbon to form a nanoparticulate refractory metal carbide that acts as a catalyst.

[0041] The first temperature zone may be at least 250°C, preferably at least 500°C, particularly preferably at least 950°C.

[0042] The second temperature zone can be at a temperature lower than the temperature of the first temperature zone. The second temperature zone can be in or downstream of a temperature-controlled flow-through furnace. The second temperature zone can be a cooling zone.

[0043] The third temperature zone may be 200°C or higher.

[0044] The fourth temperature zone can be at 500°C or higher, preferably at 700°C or higher.

[0045] Preferably, step (d) is carried out by classifying the nanoparticles of the nanoparticle refractory metal material according to their mass, aerodynamic diameter, or electrical mobility.

[0046] Step (d) may be carried out by a particle size classifier (e.g., an aerosol classifier), which may be a differential mobility classifier, an aerodynamic aerosol classifier, or a centrifugal particle mass spectrometer.

[0047] The geometric mean diameter GMD (e.g., mobility diameter) of the nanoparticle refractory metal material in the discrete stream of nanoparticle refractory metal material can be 10 nm or less, preferably 7 nm or less, and particularly preferably 3 nm or less. The geometric mean diameter (GMD) of the nanoparticle refractory metal material in the discrete stream of nanoparticle refractory metal material can be in the range of 1 to 5 nm.

[0048] The number concentration of nanoparticle refractory metal material in the discrete flow of nanoparticle refractory metal material is 10 5 cm -3 may be greater than or equal to 10 6 cm -3 More than 10, particularly preferably 7 cm -3 That's all.

[0049] Preferably, the nanoparticulate refractory metal material in the discrete stream of nanoparticulate refractory metal material is substantially monodisperse. The geometric standard deviation (GSD) of the diameters (e.g., mobility diameters) of the nanoparticulate refractory metal material is preferably less than 2, particularly preferably less than 1.5, and more preferably less than 1.1.

[0050] The geometric mean diameter (GMD) of the nanoparticle refractory metal may be 8 nm or less, preferably 5 nm or less, and particularly preferably 2 nm or less. The geometric mean diameter (GMD) of the nanoparticle refractory metal may be in the range of 1 to 5 nm.

[0051] Preferably, the method comprises: (e') introducing a discrete stream of a second nanoparticle refractory metal material into the temperature-controlled reactor.

[0052] The discrete stream of the second nanoparticle refractory metal material can be prepared by subjecting the second refractory metal material to either steps (a)-(d) together, or steps (a)-(d) performed separately on the refractory metal material. For example, steps (a)-(d) can be performed together by mixing the refractory metal compound and the second refractory metal compound or as an alloy or intermetallic compound.

[0053] The second refractory metal compound can be a W, Mo, Re, V, Nb, Ir, Ru, or Rh compound.

[0054] In a supported form, the carbon material comprising SWCNTs can be supported (eg, deposited) on a substrate.

[0055] In a self-supporting form, the carbon material comprising SWCNTs can be a powder, fiber, film, or mat.

[0056] The SWCNT-containing carbon material can be collected from the temperature-controlled flow-through reactor by displacing the SWCNT-containing carbon material as a continuous discharge through an outlet of the temperature-controlled flow-through reactor and collecting the continuous discharge. The SWCNT-containing carbon material can be displaced by mechanical, electrostatic, or magnetic forces. The continuous discharge can be collected mechanically. For example, the continuous discharge can be collected on a rotating spindle or drum.

[0057] The flow rate of the discrete stream of nanoparticulate refractory metal material in step (e) can be up to 50 g / hr (eg, about 7 g / hr).

[0058] The nanoparticle refractory metal material can be introduced (e.g., injected) into a linear, axial, vortex, helical, laminar, or turbulent flow path in step (e). The nanoparticle refractory metal material can be introduced at multiple locations. In step (e), the nanoparticle refractory metal material can be introduced axially or radially (via a probe or injector) into a temperature-controlled flow-through reactor.

[0059] Prior to step (g), the carbon source may be heated. Prior to step (g), the carbon source may be exposed to radiant heat transfer by an infrared, visible light, ultraviolet light, X-ray, radio frequency, or microwave energy source.

[0060] In step (g), the carbon source may be introduced (e.g., injected) into a linear, axial, spiral, helical, laminar, or turbulent flow channel.

[0061] In step (g), the carbon source can be introduced axially or radially into the temperature-controlled flow-through reactor. The carbon source can be introduced axially via a probe or injector. The carbon source can be introduced at multiple locations.

[0062] The carbon source may be an optionally substituted and / or optionally hydroxylated aromatic or aliphatic, acyclic or cyclic hydrocarbon (e.g., alkyne, alkane, or alkene), which is optionally interrupted by one or more heteroatoms (e.g., oxygen). Preferably, an optionally halogenated C 1-6 hydrocarbons (e.g. methane, propane, ethylene, acetylene or tetrachloroethylene), optionally mono-, di- or trisubstituted benzene derivatives (e.g. toluene) or C 1-6 - an alcohol (e.g., ethanol).

[0063] Preferably, the carbon source is methane, optionally (but preferably) in the presence of an optionally substituted and / or optionally hydroxylated aromatic or aliphatic, acyclic or cyclic hydrocarbon (e.g., alkyne, alkane or alkene), which is optionally interrupted by one or more heteroatoms (e.g., oxygen).

[0064] The carbon source is a C olefin such as methane, ethylene, or acetylene. 1-6 -can be a hydrocarbon.

[0065] The carbon source can be an alcohol, such as ethanol or butanol.

[0066] The carbon source can be an aromatic hydrocarbon such as benzene or toluene.

[0067] In a preferred embodiment, the carbon source is methane, optionally in the presence of propane or acetylene.

[0068] The flow rate of the carbon source can be in the range of 0.5 to 30,000 sccm (eg, 2,000 sccm).

[0069] Typically, in step (g), a carrier gas such as helium, hydrogen, nitrogen, or argon is introduced into the carbon source.

[0070] The temperature-controlled flow-through reactor and / or the temperature-controlled flow-through furnace may be cylindrical or have another shape. The temperature-controlled flow-through reactor and / or the temperature-controlled flow-through furnace may be substantially vertical or horizontal.

[0071] The walls of the temperature-controlled flow-through reactor and / or the temperature-controlled flow-through furnace may be selectively cooled by exposure to a cooling fluid such as water, liquid nitrogen or liquid helium.

[0072] The temperature-controlled flow-through reactor and / or the temperature-controlled flow-through furnace may be adapted to provide an axial temperature gradient. The axial temperature gradient may be non-uniform (e.g., stepped). The temperature of the temperature-controlled flow-through reactor and / or the temperature-controlled flow-through furnace may be controlled by resistance heating, plasma, or laser. The temperature profile of the temperature-controlled flow-through reactor and / or the temperature-controlled flow-through furnace may be substantially parabolic.

[0073] The temperature-controlled flow-through reactor and / or temperature-controlled flow-through furnace may be adapted to introduce reactants (e.g., via an injection nozzle, a lance, a probe, or a multi-orifice injector (e.g., a showerhead injector)).

[0074] Viewed in a further aspect, the present invention provides an assembly for producing a carbon material comprising SWCNTs, the assembly comprising: (A) an aerosolization device for generating an aerosol stream of refractory metal material suspended in a carrier gas; (B) a temperature-controlled flow-through oven operatively connected to and downstream from the aerosolization device, the temperature-controlled flow-through oven receiving a stream of refractory metal material and discharging a stream of nanoparticle refractory metal material during use; (C) a particle size classifier operably connected to and downstream of the temperature-controlled flow-through furnace, the particle size classifier, in use, separating the discrete stream of nanoparticle refractory metal material according to a selective distribution of particle sizes; (D) a temperature-controlled reactor operatively connected to and downstream of the particle size classifier, wherein, during use, the temperature-controlled reactor receives a discrete stream of nanoparticle refractory metal material, an optional stream of reducing agent, and a stream of carbon source, thereby producing a carbon material comprising SWCNTs; Equipped with.

[0075] In this aspect of the invention, the steps and features may be as previously described for similar steps and features.

[0076] Viewed in yet another aspect, the present invention provides a process for the production of a carbon material comprising SWCNTs, the process comprising: (1) generating a stream of refractory metal material suspended in a carrier gas; (2) introducing a stream of refractory metal material into a temperature-controlled flow-through furnace; (3) subjecting a stream of refractory metal material to a temperature sufficient to produce a stream of refractory metal material, wherein the stream of refractory metal material is exposed to a first temperature zone sufficient to vaporize the refractory metal material and a second temperature zone downstream of the first temperature zone, wherein the second temperature zone is sufficient to renucleate the refractory metal material to produce a stream of nanoparticulate refractory metal material; (4) separating from the stream of nanoparticle refractory metal material a discrete stream of the nanoparticle refractory metal material exhibiting a selective distribution of nanoparticle sizes; (5) exposing the optional reducing agent and the nanoparticulate refractory metal material to a third temperature zone sufficient to produce a nanoparticulate refractory metal; (6) exposing the carbon source and the nanoparticle refractory metal to a fourth temperature zone sufficient to produce the carbon material comprising SWCNTs; Including, wherein the process further comprises either depositing the nanoparticle refractory metal material on a substrate after step (4) or depositing the nanoparticle refractory metal on a substrate after step (5).

[0077] In this aspect of the invention, the steps and features may be as previously described for similar steps and features.

[0078] (A) an aerosolization device for generating an aerosol stream of refractory metal material suspended in a carrier gas; (B) a temperature-controlled flow-through oven operatively connected to and downstream of the aerosolization device, the temperature-controlled flow-through oven receiving the stream of refractory metal material and discharging a stream of nanoparticle refractory metal material during use; (C) a particle size classifier operatively connected to and downstream of said temperature-controlled flow-through furnace, said particle size classifier, in use, separating said discrete stream of nanoparticulate refractory metal material according to a selective distribution of particle sizes; (D) a first device for exposing the nanoparticulate refractory metal material to an optional reducing agent and a temperature sufficient to produce the nanoparticulate refractory metal; (E) a second device for exposing a carbon source and the nanoparticle refractory metal to a temperature sufficient to produce the carbon material comprising SWCNTs; wherein the apparatus further comprises a precipitator which is either operably connected to the particle size classifier and downstream of the particle size classifier, which, in use, deposits the nanoparticle refractory metal material onto a substrate, or a precipitator which is operably connected to the first device and downstream of the first device, which, in use, deposits the nanoparticle refractory metal onto a substrate.

[0079] In this aspect of the invention, the steps and features may be as previously described for similar steps and features.

[0080] In a preferred embodiment, the precipitator is an electrostatic precipitator.

[0081] Viewed in yet another aspect, the present invention provides a carbon material comprising SWCNTs, wherein one or more pairs of chiral indices selected from the group consisting of (2n±2,n), (2n±1,n) and (2n,n) are exhibited by a majority of the SWCNTs.

[0082] Typically, the chiral index is determined by Raman spectroscopy performed on carbon materials in the radial breathing mode region.

[0083] Preferably, in a carbon material comprising SWCNTs, the pair of chiral indices exhibited by the majority of the SWCNTs is (2n,n).

[0084] Preferably, n is an integer in the range of 4 to 7, and particularly preferably an integer in the range of 5 to 7.

[0085] The pair of chiral indices can be (12,6), (10,5), (8,4), (12,5) or (9,4).

[0086] Preferably, the pair of chiral indices is (12,6) and / or (10,5).

[0087] Preferably, the pair of chiral indices is (12,6).

[0088] Preferably, one or more pairs of chiral indices selected from the group consisting of (2n±2,n), (2n±1,n) and (2n,n) are exhibited by 50 wt% or more of the SWCNTs, particularly preferably 60 wt% or more of the SWCNTs, more preferably 75 wt% or more of the SWCNTs, even more preferably 85 wt% or more of the SWCNTs, and particularly preferably 90 wt% or more of the SWCNTs.

[0089] In yet another aspect, the present invention provides a carbon material comprising SWCNTs, wherein a chiral angle in the range of 12 to 26° (preferably 13 to 24°, particularly preferably 16 to 22°, more preferably 17 to 21°, and even more preferably 18 to 20°) is exhibited by the majority of the SWCNTs.

[0090] Preferably, the chiral angle in the range of 12 to 26° is exhibited by 50 wt% or more of the SWCNTs, particularly preferably 60 wt% or more of the SWCNTs, more preferably 75 wt% or more of the SWCNTs, even more preferably 85 wt% or more of the SWCNTs, and particularly preferably 90 wt% or more of the SWCNTs.

[0091] In a further aspect, the present invention provides a carbon material comprising SWCNTs, wherein the average chiral angle of the SWCNTs is in the range of 18 to 20°.

[0092] The invention will now be described, in a non-limiting sense, with reference to the accompanying figures in which: [Brief explanation of the drawings]

[0093] [Figure 1] 1 is a schematic diagram of an aerosol generation and size selection setup for continuous nanoparticle generation and collection, along with accompanying plots of mobility equivalent diameter taken at various stages of the method of the invention. [Figure 2]Figure 2a is an AFM image of WoNPs uniformly deposited on a SiO2 / Si substrate. It shows a particle population with a narrow size distribution, with an average diameter of approximately 1.2 nm. Figure 2b is an AFM image of WoNPs uniformly deposited on a SiO2 / Si substrate. It shows a particle population with a narrow size distribution, with an average diameter of approximately 2.0 nm. Figure 2c is an AFM image of WoNPs uniformly deposited on a SiO2 / Si substrate. It shows a particle population with a narrow size distribution, with an average diameter of approximately 3.2 nm. Figure 2d is an HRTEM image of polycrystalline MooNPs with a mobility equivalent diameter of 10 nm, corresponding to a diameter of approximately 7 nm measured by TEM and AFM. The diameter of the mNPs is approximately 60% of the diameter of the oNPs. Figure 2e is an HRTEM image of single-crystalline MomNPs after reduction and reassembly. The diameter of the mNPs is approximately 60% of the diameter of the oNPs. Figure 2f shows the observed diameter change of Mo NPs through the stages of particle generation and CNT growth for several mobility-equivalent diameters defined using DMA. The black arrow indicates a ~60% decrease in diameter between Figures 2d and 2e. During the growth stage, Mo2C retains the size of the Mo NPs, which strongly determines the diameter of the CNTs. [Figure 3] Figure 3a shows an SEM image of SWCNTs grown from (a) low-area-density NPs on a marked SiO2 / Si substrate. Figure 3b shows an SEM image of (b) high-area-density NPs on a marked SiO2 / Si substrate. Figure 3c shows XRD profiles of W, Mo, and Re catalysts at different growth stages (all nanoparticles were supported on an alumina filter). Figure 3d shows a TEM image of SWCNTs grown with 2.4 nm Mo oNPs. Figure 3e shows a TEM image of SWCNTs grown with 4.3 nm W oNPs. Figure 3f shows a TEM image of SWCNTs grown with 6.7 nm Mo oNPs. Wall-bound CNTs with more defects were rarely produced. [Figure 4]Figure 4a shows the Raman mapping results for SWCNTs grown from a W catalyst (oNP diameter approximately 2.5 nm, mNP diameter approximately 1.5 nm). The Raman spectrum in the RBM region was detected with a 532 nm laser, and all baselines were subtracted. Figure 4b shows the Raman mapping results for SWCNTs grown from a W catalyst (oNP diameter approximately 2.5 nm, mNP diameter approximately 1.5 nm). The Raman spectrum in the RBM region was detected with a 638 nm laser, and all baselines were subtracted. Figure 4c shows the Raman mapping results for SWCNTs grown from a W catalyst (oNP diameter approximately 2.5 nm, mNP diameter approximately 1.5 nm). The Raman spectrum in the RBM region was detected with a 785 nm laser, and all baselines were subtracted. Figure 4d shows the mass abundance statistics from the 532 nm laser with a normalized scale. Figure 4e shows the mass abundance statistics from the 638 nm laser with a normalized scale. Figure 4f shows the mass abundance statistics from a 785 nm laser with a normalized scale. Figure 4g shows the mass abundance statistics displayed in a graphene map for the diameter range of 0.65 to 2 nm. Figure 4h shows a graphene map of summarized abundances obtained from electron diffraction identification. Figure 4i shows the electron diffraction pattern of a (12,5) tube (left: experiment, right: simulation). [Figure 5] Figure 5a shows the equipment configuration and schematic of the floating catalytic CVD (FCCVD). Figure 5b shows the corresponding preliminary results for CNTs grown by FCCVD without size selection. Figure 5c shows the corresponding preliminary results for CNTs grown by FCCVD without size selection. Figure 5d shows the corresponding preliminary results for CNTs grown by FCCVD without size selection. [Figure 6] Figure 6 shows a portion of the modified Kataura plot for SWCNT arrays grown directly on a SiO2 / Si substrate. The laser resonance regions at 532 nm, 638 nm, and 785 nm are marked with dashed lines, and the broadening factors are set to 100 meV each. [Figure 7]Figure 7a shows the relationship between the concentration of the spray solution and the mean diameter (GMD), Figure 7b shows the relationship between the concentration of the spray solution and the standard deviation (GSD), and Figure 7c shows the relationship between the concentration of the spray solution and the concentration of oNPs measured at position IV in Figure 1. [Figure 8] Figure 8a shows the XRD pattern of W nanoparticles, Figure 8b shows the XRD pattern of Mo nanoparticles, Figure 8c shows the XRD pattern of Re nanoparticles, and Figure 8d shows the XRD pattern of Re nanoparticles formed in the presence of a carbon source. [Figure 9a] TEM images showing that SWCNTs formed aligned arrays with guidance from atomic steps when grown from NPs deposited on a sapphire substrate. The inset is an FFT of (a). [Figure 9b] TEM images showing that SWCNTs formed aligned arrays with guidance from atomic steps when grown from NPs deposited on a quartz substrate. [Figure 10] FIG. 10 is a schematic diagram of a DMA column. [Figure 11]Figure 11a shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.8 nm W oNPs detected by a 532 nm laser. Figure 11b shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.8 nm W oNPs detected by a 638 nm laser. Figure 11c shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.8 nm W oNPs detected by a 785 nm laser. Figure 11d shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.8 nm W oNPs. Results are normalized to scale and displayed on graphene maps in the diameter range 0.65-2 nm. Figure 11e shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.5 nm Mo oNPs detected by a 532 nm laser. Figure 11f shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.5 nm MoONPs detected by a 638 nm laser. Figure 11g shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.5 nm MoONPs detected by a 785 nm laser. Figure 11h shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 2.5 nm MoONPs. Results are normalized to scale and displayed on graphene maps in the diameter range of 0.65 to 2 nm. Figure 11i shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 3.0 nm ReONPs detected by a 532 nm laser. Figure 11j shows mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from approximately 3.0 nm ReONPs detected by a 638 nm laser. Figure 11k shows the mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from ∼3.0 nm Re oNPs detected by a 785 nm laser. Figure 11l shows the mass abundance statistics from Raman mapping in the RBM region of SWCNTs grown from (il) ∼3.0 nm Re oNPs.The results are normalized to scale and displayed on graphene maps in the diameter range 0.65–2 nm. [Figure 12] Figure 12a shows the results of Raman mapping of SWCNTs from Mo mNPs (approximately 1.5 nm). Figure 12b shows the results of Raman mapping of SWCNTs from Mo mNPs (approximately 1.5 nm). Figure 12c shows the results of Raman mapping of SWCNTs from Mo mNPs (approximately 1.5 nm). Figure 12d shows the abundance statistics of SWCNTs grown at low carbon (C / H approximately 6) from Mo mNPs (approximately 1.5 nm). Figure 12e shows the abundance statistics of SWCNTs grown at low carbon (C / H approximately 6) from Mo mNPs (approximately 1.5 nm). Figure 12f shows the abundance statistics of SWCNTs grown at low carbon (C / H approximately 6) from Mo mNPs (approximately 1.5 nm). [Figure 13a] HRTEM images of short CNTs from the carbon blind catalyst and W mNPs (approximately 2.6 nm) are shown. [Figure 13b] HRTEM images of short CNTs from the carbon blind catalyst and W mNPs (approximately 2.6 nm) are shown. [Figure 13c] HRTEM images of short CNTs from the carbon blind catalyst and W mNPs (approximately 2.6 nm) are shown. [Figure 13d] HRTEM images of short CNTs from carbon blind catalyst and Mo mNPs (approximately 4.5 nm) are shown. [Figure 13e] HRTEM images of short CNTs from carbon blind catalyst and Mo mNPs (approximately 4.5 nm) are shown. [Figure 13f] HRTEM images of short CNTs from carbon blind catalyst and Mo mNPs (approximately 4.5 nm) are shown. [Figure 14]Figure 14a shows a qualitative calculation of the abundance based on various coefficients. It shows a qualitative calculation of the mass abundance of SWCNTs from a liquid catalyst considering only the nucleation thermodynamic coefficients (SWCNTs are concentrated near the armchair region). Figure 14b shows a qualitative calculation of the mass abundance of SWCNTs from a liquid catalyst considering only the growth rate coefficients based on screw dislocation theory (SWCNT growth rate is proportional to the chiral angle). Figure 14c shows a qualitative calculation of the mass abundance of SWCNTs from a liquid catalyst considering both the coefficients in Figures 14a and 14b (the preferred region is around the armchair chirality, but experiments show that the abundance is primarily determined by the growth rate in Figure 14b, resulting in a broader chirality distribution with larger chiral angles). Figure 14d shows a qualitative calculation of the mass abundance of SWCNTs from a solid catalyst considering only the nucleation thermodynamic coefficients based on reported interfacial energy values ​​(SWCNTs are concentrated near the zigzag region). Figure 14e shows a qualitative calculation of the mass abundance of SWCNTs from the solid catalyst, taking into account only growth kinetics (the growth rate reaches a maximum at a chiral angle of approximately 19.1°). Figure 14f shows a qualitative calculation of the mass abundance of SWCNTs from the solid catalyst, taking into account both the coefficients in Figures 14d and 14e (the chirality is preferably close to zigzag, as reported by Penev, ES, Bets, KV, Gupta, N. & Yakobson, BI, Transient Kinetic Selectivity in Nanotubes Growth on Solid Co-W Catalyst. Nano Letters 18, 5288-5293, (2018) with the same interfacial energy value). Figure 14g shows a qualitative calculation of the mass abundance of SWCNTs from the solid catalyst, taking into account the diameter size guidance of the SWCNTs from the catalyst (the distribution is more concentrated). As shown in Figure 2a, a normal distribution with a mean diameter of 1.2 nm and a standard deviation of 0.3 nm was used.Figure 14h shows a qualitative calculation of the mass abundance of SWCNTs from a solid catalyst taking into account the chirality-dependent growth time (by growing SWCNTs in a carbon-rich environment, the chirality-dependent growth time coefficient leads to a concentration of abundance near (2n,n), with the threshold set at approximately half the poisoning). Figure 14i shows a qualitative calculation of the mass abundance of SWCNTs from a solid catalyst with a narrow distribution and thin catalyst size (0.8 ± 0.2 nm) with approximately one-quarter of the poisoning (semiconductor chiralities such as (8,4), (10,3), (9,4), and (11,3) are predicted to be enriched). (Modeling was performed for all chiralities with diameters between 0.65 and 2 nm and T = 850 °C. For liquid catalysts, the CNT-catalyst interaction energy values ​​for A- and Z-type edge atoms are 0.09 eV / atom and 0.345 eV / atom, respectively, reported for a Co(111) catalyst with a separated A|Z interface (see Bets, KV, Penev, ES & Yakobson, BI, Janus Segregation at the Carbon Nanotube-Catalyst Interface. ACS Nano, (2019)). For solid catalysts, EInt A is 0.147 eV / atom and EInt Z is 0.144 eV / atom, respectively, reported for a Co7W6 solid catalyst with a (003) W slab with a separated A|Z interface (see Bets et al. [supra]). [Example]

[0094] This example relates to an embodiment of the invention in which there is continuous gas-phase production of size-selective refractory catalysts for SWCNT chirality control. Three refractory metals were investigated: tungsten (W), molybdenum (Mo), and rhenium (Re). Figure 1 shows a schematic of the size-selection setup for aerosol generation and continuous nanoparticle generation and collection, along with accompanying plots of mobility-equivalent diameters obtained at various stages.

[0095] (NH4)6H2W 12 O40 (Sigma-Aldrich463922), (NH4)6Mo7O 24 Highly dilute aqueous metal salt solutions of NH4ReO4 (Sigma-Aldrich 09878) and NH4ReO4 (Sigma-Aldrich 316954) were prepared at a concentration of 0.3 mM per metal atom. The highly dilute aqueous solutions were atomized into droplets suspended in nitrogen through a TSI Inc. 9302 atomizer using a flow rate of 3.6 slpm. The resulting fine droplet mist (location I in Figure 1) contained solution droplets with a diameter of approximately 1.5 μm. The mist was passed through a desiccant dryer, where water was removed, leaving precipitated metal salt nanoparticles (sNPs) suspended in the carrier gas as an aerosol (location II in Figure 1). The metal sNPs were then transported to an alumina tube in a furnace set at 950 °C, where they were decomposed and calcined to form the metal oxides. Because oxides of refractory metals have high saturated vapor pressures, the metal oxides were completely evaporated in the high-temperature zone of the furnace (location III). Upon exiting the furnace and cooling, the metal oxide vapor renucleated into metal oxide nanoparticles (oNPs) (position IV in Figure 1). The use of a highly dilute salt solution allowed for simple and precise control of the input amount of metal sNPs and therefore precise control of the size of the metal oNPs at position IV.

[0096] To generate a nearly monodisperse population of metal-oNPs for collection, the polydisperse metal-oNPs from the furnace were first packed using a radioactive charge neutralizer (TSI3077) and then sent through a DMA (TSI3085), which selected a very narrow range of particles based on the ratio of charge to drag (diameter). During DMA size selection, the aerosol flow rate was set to 1.5 lpm and the DMA sheath flow was set to a maximum of 20 lpm to generate the narrowest particle size range.

[0097] To collect the nanoparticles for substrate-based growth or characterization, the DMA-sorted nanoparticles (still charged) were sent to an electrostatic precipitator, where the nanoparticles were deflected by an electric field (approximately 50 V / mm) and deposited on a target substrate (position V). The areal density (n) of oNPs on the substrate can be easily tuned by changing the deposition time (t), taking into account the aerosol concentration (c), collection efficiency (δ), aerosol flow rate (v), and substrate size (A).

[0098]

number

[0099] The concentrations of NPs before and after the precipitator were observed by a condensation particle counter (CPC, TSI 3756).

[0100] Substrate-based CVD growth of SWCNTs followed the methods outlined in Yang et al. [supra] and Zhange et al. [supra]. Specifically, various substrate-deposited oNPs in H2 were subjected to a temperature-programmed reduction process to obtain solid metal nanoparticles (mNPs). Ethanol vapor, as a carbon feedstock, was then introduced into the reaction zone in an argon carrier gas. The H2 flow rate was varied to adjust the carbon:hydrogen (C / H) ratio of the growth environment. After the set growth time, the carbon-rich environment was evacuated with H2 and then cooled to room temperature.

[0101] (Mechanism of particle size selection) DMA can select specific particle sizes between an upper limit of about 1 μm and a lower limit of about 1.7 nm. Specifically, DMA classifies particles by the ratio of charge to aerodynamic drag. If the charge state of a particle is known, the drag or "mobility" of the particle and its mobility-equivalent diameter (the diameter of a sphere that exhibits the same aerodynamic drag as the particle in question) can be determined. Thus, for roughly spherical particles, the mobility-equivalent diameter will approximate the physical diameter. Mobility is related to diameter using the following equation:

[0102]

number

[0103] where B is the mobility (also called mechanical mobility), μ is the gas viscosity, and d m is the mobility equivalent diameter, C c is the Cunningham slip correction factor (an empirical relationship that corrects for changes in particle-gas interactions during the transition, or free molecular flow regime, rather than the continuum regime). The Cunningham slip correction can be determined as follows:

[0104]

number

[0105] where λ is the mean free path of the gas molecules. From this, the charge-to-drag ratio or "electrical mobility" (Z) can be calculated from the product of the mechanical mobility and the charge of the particle:

[0106]

number

[0107] where n q is the number of charges (electrons), and e is the elementary charge.

[0108] DMA first selects the aerosol by electrical mobility by passing it through a charge neutralizer that imparts a Weidensolar charge distribution to the particle sample (see Wiedensohler, A. An approximation of the bipolar charge distribution for particles in the submicron size range. Journal of Aerosol Science 19, 387-389, (1988)). The distribution is approximately neutral overall, but contains particles with any number of charges, and is also a function of particle size. For very small particles, the majority are neutral (about 98%), and almost all charged particles gain or lose a single electron, but a very small number have at least two charges. The particles are then introduced into the "aerosol stream" Q a The DMA column is fed into the annular region between two concentric cylinders (see Figure 10). A voltage is applied to the inner cylinder, and the oppositely charged particles move radially towards this cylinder, simultaneously attracting a sheath gas flow Q sh Particles with an electrical mobility higher than the setpoint impact the cylinder and are deposited there. Particles with lower mobility are expelled with the bulk gas flow and filtered out. Particles with an electrical mobility matching the setpoint pass through a small port at the base of the inner cylinder and are transferred to the sample flow Q. s The particles are "classified" after leaving the DMA via

[0109] The schematic diagram of a DMA column in Figure 10 shows particles 1 through 5, identified from left to right, as follows: The first particle's mobility is too high, so it impacts the inner column; the second particle has a given electrical mobility and is classified; the third particle's mobility is too low, so it exits the column in the sheath flow; the fourth particle is neutral and is not affected by the electric field, so it also resides in the sheath flow; and the fifth particle has the wrong charge polarity and is repelled toward the outer column.

[0110] DMA performance is affected by the size range of catalyst particles and therefore the diameter range of CNTs. DMA classifies particles according to a triangular transfer function. This means that, theoretically, 100% of particles of a specified size will be transmitted through the DMA, with particles of larger and smaller diameters being transmitted, but with decreasing efficiency as their mobility equivalent diameter deviates from the set value. In practice, particle diffusion will result in particle losses to the cylinder walls, causing a slight broadening of the transfer function. The minimum electrical mobility (maximum mobility equivalent diameter) that is classified by the transfer function can be determined using the following relationship:

[0111]

number

[0112] where r1 and r2 are the inner and outer cylinder radii, respectively, V is the voltage between the cylinders, and L is the effective length of the column. Similarly, the maximum electrical mobility (minimum mobility equivalent diameter) classified by the DMA transfer function is equal to:

[0113]

number

[0114] In this example, Q a Q s , the peak electrical mobility (Z * ) is equal to:

[0115]

number

[0116] If the sheath flow is held constant, the voltage between the cylinders determines the classified electrical mobility. Furthermore, the gas flow rate determines the width of the transfer function (i.e., the size range of the classified particles). Specifically, the width is determined by the ratio of the sheath gas in the DMA to the sample flow entering and exiting the DMA. The ratio of sheath flow rate to sample flow rate is known as the resolution and corresponds to the normalized full width at half maximum of the transfer function. Therefore, it is important to maximize the DMA resolution to produce the narrowest range of catalyst particles. For a triangular distribution, the normalized full width at half maximum is half the difference between the minimum and maximum transmitted electrical mobility divided by the peak electrical mobility.

[0117]

number

[0118] As noted above, the narrowest size range of particles is separated when the DMA sheath flow is large compared to the aerosol / sample flow. Fortunately, electrical mobility is proportional to the sheath flow rate. That is, when the sheath flow rate is high, the largest electrical mobility, and therefore the smallest mobility-equivalent diameter, can be separated. Therefore, it is important to maximize this value, as both size range and transfer function resolution are favored at high sheath flow rates. In this example, the aerosol flow rate was set to 1.5 lpm and the sheath flow rate to 20 lpm. This corresponds to a resolution of 13.3, which is greater than the standard resolution of 10.

[0119] While charged particles can certainly be classified using DMA, it remains to be determined whether small, uncharged particles can move through the DMA via Brownian motion fast enough to also be classified. This phenomenon can be confirmed by calculating the approximate distance a particle can diffuse given the length of time the aerosol spends in the DMA. The one-dimensional root-mean-square diffusion distance (x rms ) can be determined as follows:

[0120]

number

[0121] where D is the diffusion constant of the particle and t is the diffusion time. The diffusion constant is equal to:

[0122]

number

[0123] where k is the Boltzmann constant, T is the temperature, and B is the mechanical mobility as defined above. The diffusion time is determined by calculating the velocity within the annular region of the DMA and combining this value with the effective DMA length. The diffusion time (t) of the DMA is:

[0124]

number

[0125] where L is the length of the DMA, V → is the gas velocity, Q is the volumetric flow rate, A is the annular cross section within the DMA, and r o and r i are the outer and inner radii of the DMA column, respectively.

[0126] Using the Model 3085 DMA geometry, 1.5 lpm aerosol flow, 20 lpm sheath flow, and standard air conditions as the carrier gas, a 1 nm particle would diffuse 1.13 mm. Compared to the annular gap distance of approximately 10 mm, this diffusion rate is not sufficient to transport neutral NPs to the target substrate, especially considering that this calculation is one-dimensional and that, in reality, part of the particle's Brownian motion may also be in the axial and circumferential directions of the DMA.

[0127] (characteristic evaluation) The particle size distribution was analyzed using a scanning mobility particle sorting spectrometer (SMPS), which consists of a combination of a DMA and a CPC. The DMA scans the particle size range, and the CPC records the corresponding number concentration (specifically, the particle's mobility equivalent diameter) for each size bin. The vertical axis of Figure 1 shows the ratio dN / dlogd. m represents the number concentration in that bin normalized by the bin width. The measured data were fitted using a log-normal distribution, a standard technique in aerosol science. These provide the geometric mean diameter (GMD, peak position), geometric standard deviation (GSD, width) and total number concentration (N tot , area under distribution).

[0128] AFM was performed on a Veeco DimensionProAFM in Peakforce mode.

[0129] HRTEM was performed on an FEI Talos F200X TEM (200 kV for NPs and 80 kV for CNTs), and oNPs were collected on Si3N4 grids. The reduction and CNT growth steps were performed in situ on the Si3N4 grids before characterization.

[0130] Electron diffraction (ED) of the suspended CNTs was performed on a FEITecnai F20FEGTEM in STEM nanobeam mode operating at 80 kV. Occasionally, holes were drilled in the Si3N4 grid with the grown CNTs to obtain suspended CNTs extending from the substrate.

[0131] For XRD characterization, the oNPs were vacuum filtered through an Anodisc aluminum oxide membrane filter (AAO, Whatman FIL3010). The size of the oNPs was controlled and constrained by the concentration of the salt solution. The oNPs on the AAO were reduced in H2, resulting in mNPs, which were used for conventional CNT growth. XRD characterization was performed at each stage.

[0132] Raman mapping was performed in the RBM range (70–350 cm-1) using 532, 638, and 785 nm lasers. Details are shown in Table 1. The laser spot raster-scanned randomly aligned CNTs grown on a SiO2 / Si substrate with position marks. The step size was set to 3 μm in both the x and y directions. Each spectral peak in the RBM Raman map was identified after background subtraction and associated with its chirality based on the Kataura plot (see Kataura, H. et al. Optical properties of single-wall carbon nanotubes. Synthetic Metals 103, 2555–2558, doi:https: / / doi.org / 10.1016 / S0379-6779(98)00278-1 (1999)). Abundance statistics obtained with the various lasers were normalized by pixel number and pixel size.

[0133] [Table 1]

[0134] To determine (n,m) based on the Kataura plot, Eii and ωRBM-dt are known to be strongly affected by the environment in which the CNT is placed. Using the Kataura plot with appropriate environmental corrections is essential for reliable identification. Therefore, we used the modified Kataura plot shown in Figure 6. For all data, the starting point was experimental data on nanotube optical transitions developed from suspended single-isolated SWCNTs based on electron diffraction and Rayleigh scattering (see Liu KH et al. An atlas of carbon nanotube optical transitions. Nat. Nanotechnol. 7, 325-329, doi:10.1038 / Nnano.2012.52 (2012)). Due to the environmental interaction between the SWCNT and the silica substrate, Eii was modified by a red shift of 40 meV. The resonance window (broadening factor) was set to 100 meV (see Saito, R., Hofmann, M., Dresselhaus, G., Jorio, A. & Dresselhaus, MS Raman spectroscopy of graphene and carbon nanotubes. Adv. Phys. 60, 413-550, doi:10.1080 / 00018732.2011.582251 (2011)). Some metallic thin SWCNTs may have larger values ​​due to exciton-phonon coupling (see Doorn, SK, Araujo, PT, Hata, K. & Jorio, A. Excitons and exciton-phonon coupling in metallic single-walled carbon nanotubes: Resonance Raman spectroscopy. Phys. Rev. B 78, 165408, doi:10.1103 / PhysRevB.78.165408 (2008)), which was also taken into account during the identification of (n,m). The ωRBM-dt relationship is similar to the reported ωRBM=235.9 / dt for SWNTs grown on SiO2 / Si substrates. t+5.5 (see Zhang, D. et al. (n,m) Assignments and quantification for single-walled carbon nanotubes on SiO2 / Si substrates by resonant Raman spectroscopy. Nanoscale 7, 10719-10727, doi:10.1039 / C5NR01076D (2015)).

[0135] As shown in Figure 6, the RBM is 155 cm -1 Chiralities located below this diameter (corresponding diameter of approximately 1.76 nm) are densely distributed. Considering the Raman resolution, a clear distinction is not possible. Therefore, it was only possible to accurately calculate the abundance of chiralities in SWCNTs with small diameters. Peaks with larger diameters were counted but not assigned to a specific chirality.

[0136] To account for the apparent proportion of chirality and multiple same-chirality tubes under the same laser spot, -1 )~1.53nm(160cm -1 ) range, was followed (see Zhang [supra]).

[0137] (result) Figure 1 shows the aerosol size distributions of sNPs, oNPs, and size-sorted oNPs at Re at positions II, IV, and V. The peak position, peak width (height-independent), and total number concentration of the nanoparticle size distribution are expressed as the geometric mean diameter (GMD), geometric standard deviation (GSD), and N tot It is described by:

[0138] After drying the solution droplets (position II in Figure 1), the sNPs have a mobility-equivalent diameter of several tens of nanometers and a wide distribution. Figure 1 shows sNPs with a GMD of 55 nm and a GSD of 1.83. This distribution is very broad, considering that the equilibrium logarithmic aerosol size distribution has a GSD of approximately 1.4. These particles are clearly too large and polydisperse for SWCNT growth. Vaporization and renucleation in the furnace produce a very high concentration of very small oxide particles (as shown in position IV). The oNPs are an order of magnitude smaller in size (GMD of 4.8 nm), nearly two orders of magnitude more numerous than the previous sNPs. The distribution is also narrow, with a GSD of 1.38, which is very close to the equilibrium or "self-preserving" size distribution. Considering this GMD and GSD, the full width at half maximum of the distribution is 3.7 nm. Thus, after renucleation, the size of the oNPs is pre-limited. The primary size of the oNPs can also be pre-tuned by varying the concentration of the spray solution (see Figure 7).

[0139] Although the peak size of the oNPs at position IV is much smaller than the sNPs at position II, the distribution is still polydisperse. To obtain an even narrower size range, a DMA was used at position V, with the output distribution set to a specified GMD of 4.15 nm. The resulting GMD was 4.31 nm, so the SMPS scan shows excellent agreement with this setting. The distribution was very narrow (almost monodisperse), with a GSD of only 1.05. A GSD of 1 represents an infinitely thin distribution of particles of exactly one size (completely monodisperse).

[0140] After passing through the DMA, the full width at half maximum of the size distribution will be 7.5% of the set value. For a set value of 4.15 nm, this corresponds to a very narrow full width at half maximum of 0.31 nm. In reality, the distribution broadened slightly, to about 0.52 nm. The width of the distribution is proportional to the midpoint setting, so choosing a smaller size results in a corresponding smaller full width at half maximum.

[0141] Using AFM and TEM, we accurately characterized the size distribution of the NPs. As shown in Figures 2a–c, particles of various narrow size ranges were uniformly deposited on the target substrate by electrostatic precipitator. The size of the NPs could be precisely adjusted by changing the DMA settings (see Figure 2f), with smaller DMA settings resulting in a narrower corresponding distribution. Regardless of size, the size distribution of the deposited NPs used for SWCNT growth was narrow, with a standard deviation (σ) of up to 0.6 nm. A distribution as narrow as that observed in this example is difficult to achieve from other methods; to date, all other methods rely on either complex manufacturing techniques or specialized, expensive precursors, and are often batch processes that depend on specific substrate compositions. The method of the present invention in this example is capable of continuously producing nanoparticles with a narrow distribution that can be directly deposited on any substrate.

[0142] At the time of collection, the NPs were in the oxidized metallic form (as determined from the XRD profile shown in Figure 8). From HRTEM (see the inset in Figure 2d), the oNPs appeared as densely packed polycrystalline. After reduction in H2 at high temperature, the oNPs reconstructed into single-crystalline elemental mNPs (see Figure 2e). Figure 2f summarizes the HRTEM results of the size distribution at various stages. Upon reduction and reconstruction, the diameter of the mNPs was reduced to approximately 60% of the diameter of the as-collected oNPs (black arrows in Figure 2f). During carbon growth, the catalyst particles did not show a significant change in diameter compared to the mNPs. The size of the mNPs closely matched the diameter of the corresponding CNTs.

[0143] XRD profiles are shown in Figures 3c and 8. oNPs were reduced with H2 to form mNPs. By introducing a carbon source, mNPs supported the growth of CNTs. Figures 3c and 8 show that W and Mo formed WC and Mo2C, respectively, during the growth process, while Re retained its elemental state. Mo2C was in the orthorhombic crystal system and space group Pbcn (point group D). 2h In contrast, WC and Re each have the space group P6m2 (point group D 3h) and P63 / mmc (point group D 6h ) exhibit a hexagonal crystal system with a crystalline structure. WC, Mo2C, and Re have very high melting points, allowing them to maintain a solid state during growth. Importantly, this feature allows the catalysts to surpass liquid catalysts in their ability to reliably control the chirality of SWCNTs. Maintaining a solid state during reduction and growth also makes size selection more valuable compared to liquid catalysts, as Ostwald ripening is suppressed. Regarding Figure 8d, the ReC pattern overlaps with a partial pattern of Al2O3. Therefore, the profiles of the ReMn NPs and Re catalysts with a peak around 46° were normalized. The peaks in the two profiles around 61°, 33°, and 36° are also consistent with Al2O3, ruling out the presence of ReC.

[0144] During XRD characterization, it is difficult to prevent oNPs (especially Re-oNPs) from absorbing water vapor from the environment and forming hydrates or weak acids. Sodium ions in oNPs are unavoidable impurities. However, the catalyst was not affected by the impurities. The amorphous AAO was partially reduced and annealed during reduction and growth.

[0145] (SWCNT growth and catalyst constraints) Using typical growth parameters, the concentration of SWCNTs was controlled by varying the areal density of the deposited oNPs. This was achieved simply by changing the collection time. Low and high areal density cases are shown in Figures 3a and 3b, respectively. Due to the gas-phase nature of the catalyst formation, the particles are substrate-independent. Various substrates can be used to support the oNPs for SWCNT growth. In the marked SiO2 / Si substrates (Figures 3a and 3b), random SWCNTs were grown directly without an ex situ transfer process. Aligned SWCNT arrays were also synthesized by step guidance from sapphire and ST-cut quartz substrates (see Figure 9).

[0146] As shown in Figures 3d-f, the diameter of SWCNTs is strongly influenced by the size of the mNPs and ultimately the preceding oNPs (Figure 2f). Most SWCNTs grown on a given substrate exhibit similar diameters. These results again confirm the dominant role of catalyst size on the resulting SWCNT structure. With approximately 6.7 nm oNPs (approximately 4.5 nm mNPs), the primary product was several tens of micrometers long, few-walled CNTs with numerous kinks (Figure 3f). With approximately 4.3 nm oNPs (approximately 2.6 nm mNPs), longer, higher-quality SWCNTs with diameters of approximately 3 nm were grown (Figure 3e). With approximately 2.4 nm oNPs (approximately 1.4 nm mNPs), SWCNTs with diameters of approximately 1.5 nm dominated (Figure 3d). With these small, narrowly distributed sized oNPs (typically less than 2.5 nm, mNPs less than 1.5 nm), fine chirality control of SWCNTs was achieved.

[0147] TEM shows that tangential growth of CNTs from solid catalysts results in a "peapod" structure (see Figure 3e and f), with the catalyst maintaining its spherical shape without reforming as occurs with liquid catalysts. It is noteworthy that regardless of whether the CNTs grew normally or not, the catalyst was frequently found to be completely surrounded by a layer of carbon (Figures 3e, f, and Figure 13).

[0148] (Restriction of chirality by solid catalysts) The chirality distribution or abundance of SWCNTs was primarily characterized by Raman RBM (radial breathing mode) mapping of randomly distributed SWCNTs grown on the marked substrates shown in Figure 3a. As a highly efficient, low-cost, and non-destructive characterization method, resonance Raman (RR) spectroscopy remains an essential characterization method for SWCNT chirality identification, especially for large-area statistics of SWCNTs grown on substrates. Using 532, 638, and 785 nm lasers, SWCNTs of different chiralities exhibit excitation responses corresponding to those seen in the Kataura plot (with corresponding rectification of environmental factors) and diameter-dependent RBM peaks. Using Raman xy-2D mapping, the surface was raster-scanned with the laser spot to acquire spectra for each pixel. This describes the abundance of SWCNTs in terms of both the number of tubes and the length of each tube, i.e., mass abundance. Mass abundance is more reflected by the frequency of occurrence of the corresponding RBM peak than by its height. Peaks were extracted from each pixel of the map and cumulatively displayed in Figures 4a-c. The statistical abundance of each peak was obtained from each sample using three excitation laser wavelengths (Figure 4d–f) and compiled in a graphene map (Figure 4g).

[0149] The Kataura plot (see Figure 6) shows that chiralities with diameters greater than 1.57 nm (RBM peak approximately 155 cm) -1 ) are too densely packed to clearly identify the chirality index. To ensure clear identification, the graphene map is painted with a diameter of less than 1.57 nm (the RBM peak at approximately 155 cm, represented by the blue dashed line in Figure 4a–g). -1 ), but used abundance values ​​based on all possible SWCNTs. For chiralities that cannot be resonated with the 532, 638, and 785 nm lasers, the honeycomb cell remains empty. Chiralities near (2n,n) are likely concentrated and can hardly be found near the zigzag region.

[0150] Nanobeam electron diffraction (ED) was also used to determine the chirality of the CNTs, and the results are summarized in the graphene map shown in Figure 4h. Although inefficient, ED is the best method for unambiguously recognizing the (n,m) chirality of all possible tubes. The ED pattern (Figure 4i) was obtained from a suspended CNT occasionally extending from the substrate. Due to this method, the abundance deviates from mass abundance to tube abundance, and information about the tube length is lacking. However, this technique provides more clues about the tube nucleation conditions and may still confirm the preferred chirality near (2n,n).

[0151] For W (oNP diameter ~2.5 nm, mNP diameter ~1.5 nm) from Figure 4g, the most enriched chiralities apparent are (12,6), (10,5), (8,4), (12,5), and (9,4), which are arranged around (2n,n) with a chiral angle close to 19.1°. The maximum mass abundances of (12,6), (10,5), and (8,4) reached approximately 30%, 20%, and 15% in the thin SWCNTs (0.81–1.52 nm, the range where clear distinction is possible), and approximately 20%, 15%, and 10% in the range from 0.81–2 nm. All apparent (2n,n), (2n±1,n), and (2n±2,n) chiralities reached nearly 90% among the thin SWCNTs. In contrast to the nearly zigzag or armchair regions, chiralities were barely distinguishable. If the abundances were not overestimated for the neighboring chiralities (10,5) and (13,8), (15,5) and (14,7), respectively, only (8,7) and (11,10) have moderate abundances (see the modified Kataura plot shown in Figure 6). For all the obvious (2n,n), (2n±1,n), and (2n±2,n) chiralities (compared to tubes of the same diameter, respectively), only (10,4) and (11,5) are significantly enriched. Considering both (10,4) and (11,5), the ED results show high abundances and the E of (10,4) and (11,5) located near the edge of the 0.1 eV resonance window of the 532 or 638 nm laser. 11 Lcan be seen, and the small abundance still appears to be due to poor resonance conditions. 11 H also appears to have poor resonance with the 532 nm laser.

[0152] For the ED results, a concentrated distribution of diameters less than 1.3 nm can also be seen, which explains the lower abundance of (13,6), (14,7), and (16,7) compared to (12,6), (10,5), and (8,4) in Figures 4d-f. As noted above, ED reveals information about the amount of tubes and, therefore, the conditions for tube nucleation. Based on the results, tubes with a chiral angle of 19±5° remain enriched. While some zigzag-shaped tubes appear, armchair-shaped tubes are not identified. The appearance of zigzag-shaped tubes is attributed to enrichment during nucleation. The broader chirality distribution from ED compared to Raman RBM mapping can be explained by the recently reported A|Z segregation at the interface of solid catalyst tubes, which significantly reduces the interfacial energy for all chiral tubes, thereby broadening the equilibrium CNT nucleation probability distribution.

[0153] Compared to WC, Mo2C and Re show similar trends, producing closer (2n,n) chirality (Figures 11e-l), but also exhibit some unique chirality selection. Compared to WC, Mo2C produced moderate abundances of (8,5), (9,6), (14,4), and (13,4), but less abundant (7,6), (10,6), and (8,4). In the case of Re, (9,4), (11,4), and (12,5) were abundant, but (8,5) was scarce. With solid catalysts and similar CVD parameters, the product was enriched in closer (2n,n) tubes. However, differences in interfacial energy between the tubes and catalyst and the resulting differences in nucleation and growth lead to minor differences between these catalysts. Indeed, this study represents the first time that chirality-controlled SWCNTs have been grown from Re, inherently maintaining their elemental and solid state after growth.

[0154] As mentioned above, the point groups of WC, Mo2C, and Re differ in their corresponding 3-, 2-, and 6-fold symmetries, respectively. However, based on the statistical results of the experimental results, WC, Mo2C, and Re produce more SWCNTs near the (2n,n) chirality, and the rarest detected chirality is always located toward the zigzag (ZZ) and armchair (AC) regions of the graphene map (W in Figure 4 and Mo, Re in Figure 11). (12,6) and (10,5) SWCNTs with 6- and 5-fold symmetries are abundant in all three catalysts. The symmetry of the catalyst appears to have a limited effect on the abundance of SWCNT chiralities.

[0155] In addition to the requirement for a solid catalyst for chirality selection, the carbon to hydrogen ratio also proves to be important. With excess carbon supply (C:H > 1:15), chirality selection becomes more pronounced, with (12,6) and (10,5) always dominating, and all chiralities positioned near the (2n,n) line. In contrast, for C / H < 1:5 (see Figure 12), chirality control is less evident. Many other chiralities are observed in abundances comparable to those near the (2n,n) line.

[0156] Based on the growth results, the best chirality control can only be achieved if the catalyst size is sufficiently small, typically less than 3 nm in oNP diameter. Larger diameter catalysts produce more tubes with larger diameters, resulting in more chirality. Furthermore, tangential growth is dominant, and the correct positive correlation between catalyst and SWCNT diameter is also verified by HRTEM (see Figures 3 and 13). By maintaining a solid state during growth, the catalyst retains a fixed diameter, which is essential for achieving chirality control.

[0157] Furthermore, unlike Fe, Co, and Ni catalysts, the solid W, Re, and Mo catalysts have relatively low oxidation temperatures in air, making them easily removable after CVD, leaving behind pure CNTs on the target substrate.

[0158] (Qualitative Modeling) We investigated the factors behind the tube-catalyst interface thermodynamics during nucleation, growth kinetics and self-developing chirality-dependent growth time without a symmetric matching mechanism to understand the observed preferential chirality distribution.

[0159] As reported by Artyukhov [supra], the mass-based abundance of (n,m) SWCNTs at time t is given by the integral:

[0160]

number

[0161] where p(τ,n,m) and v(τ,n,m) are the cumulative probability and growth rate of the catalyst growing an (n,m) SWCNT at time τ, respectively. Based on the assumption that growth time is chirality independent, all time terms were separated from the chirality-dependent term (n,m) in Eq. 2 as follows:

[0162]

number

[0163] where N(n,m) is the nucleation probability of (n,m) SWCNTs from the catalyst, R(n,m) is the growth rate of (n,m) SWCNTs, and S(t) is the set of all periods.

[0164] However, Eq. 3 is only valid when catalyst deactivation is independent of chirality or when the catalyst is always active and therefore CNT length is limited only by the growth rate. However, after CNT synthesis, inactive catalysts are always observed along with relatively short CNTs (see Figure 13). Catalyst deactivation can be attributed to the ever-increasing surface carbon, which is not efficiently supplied to promote SWCNT growth. As shown in Figures 3e and 3f, the catalyst was always surrounded by carbon caps, resulting in a "peapod" morphology. This phenomenon may be more evident when using inefficient solid catalysts, such as iron, rather than efficient liquid catalysts.

[0165] Furthermore, differences in growth kinetics can lead to catalyst deactivation as a function of chirality. Only chiralities with sufficient growth rates are able to incorporate incoming carbon toward CNT growth rather than surface accumulation and catalyst poisoning. Therefore, in addition to faster growth rates, these chiralities can also extend their growth time before being terminated by catalyst poisoning. If the growth rate of a particular chirality is sufficiently fast, the carbon supply rate becomes the limiting factor for CNT growth rate and CNT length. In summary, the chirality-dependent growth time difference coefficient should be distinguished from the growth rate coefficient.

[0166] Here, the phenomenologically involved is the trapping rate R, which is proportional to the rate of carbon incident on the catalyst to either promote CNT growth or hinder it. trap Another parameter is the carbon-tolerance capacity of the catalyst, U(d). With the knowledge that the catalyst is solid during growth and that carbon surface diffusion is the dominant growth mode rather than bulk diffusion, U(d) was assumed to be proportional to the catalyst surface area. Then, the abundance of (n,m)-SWCNTs at time t can be modified as follows:

[0167]

number

[0168] where V(n,m,t) is the growth rate term, which accounts for the chirality dependent growth time.

[0169]

number

[0170] where t is the set growth time during the experiment. Furthermore, when t is long enough, random termination of CNT growth due to defect formation, etc. will form an upper limit on t.

[0171] V(n,m,t) indicates that growth is constrained by either the carbon supply (Eq. 5.1), growth time (Eq. 5.2), or catalyst carbon tolerance (Eq. 5.3).

[0172] Additional modeling details related to abundance calculations are provided in the appendix below.

[0173] When the C:H ratio is low, SWCNT growth can be limited by the carbon supply (Eq. 5.1) (except for zigzag and armchair SWCNTs, whose growth rates are too slow). In this case, differences in nucleation preferences govern the resulting chirality distribution. In the case of solid catalysts, the thermodynamic preferences are primarily driven by different catalyst-tube interfacial energies (E Int Z ,E Int A ) values. As mentioned above, the newly reported A|Z segregation at the interface significantly reduces the interfacial energy for all chiral tubes and broadens the equilibrium CNT nucleation probability distribution. Growth can terminate by a set time or randomly due to defects.

[0174] In contrast, when the growth environment is enriched with carbon, the slow-growing SWCNTs poison the catalyst much faster, leaving only the fast-growing chiralities to continue growing, resulting in a higher mass-based abundance of these fast-growing chiralities in the product. On the solid catalyst, the growth rate is bimodal, with minima at the AC and ZZ edges and a maximum at the 19.1° line for (2n,n) SWCNTs (see Figure 14e). The resulting abundance distribution favors the (2n,n), (2n±1,n), and (2n±2,n) chiralities (see Figure 14h), confirming the experimental abundance results.

[0175] In addition to the nucleation thermodynamics, growth kinetics, and chirality-dependent growth time, the catalyst size directly determines the domain of possible chiralities and thereby influences the final chirality abundance (compare Figure 14f–g with Figure 14h–i).

[0176] Growth from liquid catalysts was also modeled and is shown in Figures 14a-c. Using the same set of modeling parameters, AC and near-AC SWCNTs are favored, primarily due to growth rates proportional to the chiral angle. However, due to Ostwald ripening, liquid catalysts tend to have a much broader size distribution than solid catalysts, resulting in a correspondingly broader distribution of SWCNT diameters and chiralities. Due to the very low energy barrier, nucleation of SWCNTs from liquid catalysts is also disordered.

[0177] (Conclusion) Due to the gas-phase nature of the catalyst formation process, the particles are substrate-independent. Therefore, the substrate can be completely removed, realizing a fully continuous process. By incorporating hydrogen and carbon sources into the gas line, continuous floating catalyst CVD (FCCVD) growth from a solid catalyst was achieved for the first time (see Figure 5). Figures 5b and 5c show preliminary products from FCCVD using a W solid catalyst. To increase the CNT production rate, FCCVD growth was performed using large catalysts (oNPs >5 nm) without fine size selection. The relatively low efficiency of solid catalysts, the sensitivity of refractory metal oxides to reduction processes, and the lack of carbon transfer from the substrate to the catalyst presented additional challenges compared to conventional liquid catalysts.

[0178] A highly adaptable method for producing nearly monodisperse W, Mo, and Re oxide nanoparticles with diameters less than 2 nm was achieved through an aerosol-based size-selection method. These nanoparticles were reduced to form solid catalysts capable of producing CNTs with well-controlled diameter and chirality distributions. Despite known symmetry matching and epitaxial growth, the chirality control mechanism was attributed not only to differences in growth rates between chiralities but also to the extended growth time available for rapidly growing CNTs. In a high-carbon growth environment, the three metals produced SWCNTs with similar (2n,n) chirality, with particularly high abundances of (12,6) and (10,5). Chiralities with a chiral angle of 19±5° were particularly common, exceeding 90% abundance. Thanks to the aerosol method for producing precisely sized NPs, continuous production of chirality-controlled SWCNTs is achievable, which may help increase the impact of this remarkable material in many fields of science and engineering.

[0179] (Appendix) As reported by Artyukhov [supra], at time t, the abundance of (n,m) SWCNTs is given by the integral:

[0180]

number

[0181] where p(t,n,m) and v(t,n,m) are the cumulative probability and growth rate that this catalyst will grow an (n,m) SWCNT at time t.

[0182] As described above, taking into account the chirality-dependent growth time difference coefficient, the abundance of (n,m)SWCNTs at time t is modified as follows:

[0183]

number

[0184] where N(n,m) is the nucleation probability of an (n,m) SWCNT from the catalyst, and V(n,m,t) is a growth rate term, accounting for the chirality-dependent growth time.

[0185]

number

[0186] where t is the growth time set during the experiment. V(n,m,t) concludes that growth is constrained by either the carbon supply (Eq.5.1), the growth time (Eq.5.2), or the catalyst carbon tolerance (Eq.5.3). R trap is the trapping rate proportional to the carbon incidence rate on the catalyst; U(d) is the carbon capacity of the catalyst, and d is the diameter of the SWCNT; R(n,m) is the growth rate of the (n,m) SWCNT.

[0187] As reported by Artyukhov [supra], the thermodynamic model during nucleation is as follows:

number

[0188] where Γ n,m is the contact interfacial energy between the CNT edge and the catalyst, and G n,mcap is the cap-free energy.

[0189]

number

[0190] where E int A,Z is the CNT-catalyst interaction energy of the A or Z type edge atom.

[0191]

number

[0192] α=0.039 eV nm 2 / atom is the bending stiffness of graphene, and d is the diameter of the (n,m) SWCNT.

[0193]

number

[0194] where E n,m cap is the elastic energy of the CNT cap, which is constant for a hemispherical elastic shell. S n,m cap and N n,m cap are the cap entropy and cap number of the (n, m) chirality SWCNT, respectively. k B is the Boltzmann constant.

[0195] At the CNT-solid catalyst interface, theoretical modeling reported reconstructed asymmetric CNT edges (separated A|Z edges) and chirality-dependent defect formation. The former results indicate preferential nucleation of tubes with n > 2m, while chiral tubes with n < 2m grow much faster, significantly relieving the unfavorable nucleation of chiral SWCNTs. The latter results further revealed that the (12,6) A|Z separated interface has the lowest probability of defect formation and appears as a "transient attractor" in the Z-to-A chirality evolution trend. Here, because the separated A|Z edges are reported, only the cap entropy was considered instead of adding the entropy of the interface configuration.

[0196] However, due to the lack of kinetic Monte Carlo (kMC) simulation capabilities, a conventional circular edge interface was used, which yields abundances similar to the kMC results without chirality switching. The lack of chirality switching from defect formation would further increase the abundance of (2n,n) tubes.

[0197] For the solid catalyst, E of 0.147 eV / atom, in accordance with the value reported for the Co7W6 solid catalyst on a W slab. Int A and E of 0.144 eV / atom Int Z For liquid catalysts, an E of 0.09 eV / atom was used, as reported for a Co(111) catalyst with a separated A|Z interface. Int A and E of 0.345 eV / atom Int Z was used. Given E Int A,Z As shown in Figure 14a for a liquid catalyst with a value of E, the nucleation thermodynamics leads to enriched chiralities with large chiral angles. Int A,Z For solid catalysts with values, nucleation tends to favor smaller chiral angles but with a wider distribution (see Figure 14d).

[0198] Regarding growth kinetics, due to the lack of kinetic Monte Carlo (kMC) simulation capability, a conventional circular edge interface is used, and the growth rate R(n,m) is given as follows:

[0199]

number

[0200]

number

[0201] For liquid catalysts based on screw dislocation theory, the cost E of creating a kink pair on the A edge is Int A is nearly zero, and as a result, the growth rate of SWCNTs is proportional to the chiral angle (see Figure 14b). For the combined results of nucleation thermodynamics and growth kinetics, the favorable region is around armchair chirality (see Figure 14c). The abundance is primarily determined by growth kinetics, resulting in a more widely distributed chirality at large chiral angles.

[0202] However, on a solid surface, creating a kink pair destroys the perfect contact between the CNT and the substrate, resulting in E Int A and E Int Z and all have significant magnitudes, with the dependence being smallest at the A and Z edges and largest bimodal at 19.1° (see Figure 14e). The combined effect on abundance favors (n,1) and (n,2) chiralities (see Figure 14f).

[0203] Choosing the catalyst size shifts the abundance distribution due to the inductive effect of the catalyst (see Figure 14g). Furthermore, if the catalyst is too large, the resulting CNTs will contain more CNTs with fewer walls, which impairs chirality control.

[0204] In the carbon-rich environment, a chirality-dependent growth time coefficient was developed. The threshold was set in Figure 14e. For a given E Int A,Z For example values, when set in the range 0.65–2 nm, where approximately half of the chirality is constrained, the abundance distribution shifts to 19.1° and primarily enriches in (12,6) (see Figure 14h).

[0205] Due to the narrower catalyst distribution, thinner size (0.8 ± 0.2 nm), and appropriately limited growth time of some slow-growing SWCNTs, semiconducting chiralities such as (8,4), (10,3), (9,4), and (11,3) are expected to be enriched (see Figure 14i).

Claims

1. 1. A method for producing a carbon material comprising SWCNTs, the method comprising: (a) producing a stream of refractory metal material suspended in a carrier gas; (b) introducing said stream of said refractory metal material into a temperature controlled flow-through furnace; (c) subjecting said stream of said refractory metal material to a temperature sufficient to produce a stream of refractory metal substance; subjecting the stream of refractory metal material to a temperature sufficient to produce a stream of refractory metal material, wherein the stream of refractory metal material is exposed to a first temperature zone sufficient to vaporize the refractory metal material and a second temperature zone downstream of the first temperature zone, wherein the second temperature zone is sufficient to renucleate the refractory metal material to produce a stream of nanoparticle refractory metal material; (d) separating from said stream of said nanoparticle refractory metal material a discrete stream of said nanoparticle refractory metal material exhibiting a selective distribution of nanoparticle sizes; (e) introducing the discrete stream of the nanoparticle refractory metal material into a temperature-controlled reactor; (f) optionally, discharging a stream of reducing agent into the temperature-controlled reactor, wherein the stream of reducing agent and the discrete stream of nanoparticle refractory metal material are exposed to a third temperature zone sufficient to produce a stream of nanoparticle refractory metal; (g) discharging a stream of carbon source into said temperature-controlled reactor; (h) exposing the nanoparticle refractory metal and the carbon source to a fourth temperature zone sufficient to produce the carbon material comprising SWCNTs that can be adapted into a supported or self-supporting form within the temperature-controlled reactor or collected from the temperature-controlled reactor; A method for producing a carbon material comprising SWCNTs, comprising:

2. The method of claim 1 , wherein the refractory metal material is W, Mo, or Re.

3. 3. The method of claim 1 or 2, wherein step (d) is carried out by classifying the nanoparticles of the nanoparticle refractory metal material according to their mass, aerodynamic diameter, or electrical mobility.

4. 4. The method of claim 1, wherein the nanoparticulate refractory metal material in the discrete stream has a geometric mean diameter (GMD) of 3 nm or less.

5. The number concentration of the nanoparticle refractory metal material in the discrete stream of nanoparticle refractory metal material is 10 ７ cm －３ The method according to any one of claims 1 to 4.

6. 5. The method of claim 4, wherein the geometric mean diameter (GMD) of the nanoparticulate refractory metal material is less than or equal to 2 nm.

7. 7. The method of claim 1, wherein the nanoparticle refractory metal material in the discrete stream of nanoparticle refractory metal material is substantially monodisperse.

8. 8. The method of claim 1, wherein the nanoparticulate refractory metal material has a geometric standard deviation (GSD) of diameters of less than 1.

1.

9. 9. The method of any one of claims 1 to 8, further comprising: (e') introducing a discrete stream of a second nanoparticle refractory metal material into the temperature-controlled reactor.

10. 1. A process for producing a carbon material comprising SWCNTs, the process comprising: (1) generating a flow of refractory metal material suspended in a carrier gas; (2) introducing the stream of refractory metal material into a temperature-controlled flow-through furnace; (3) subjecting the stream of refractory metal material to a temperature sufficient to produce a stream of refractory metal material, wherein the stream of refractory metal material is exposed to a first temperature zone sufficient to vaporize the refractory metal material and a second temperature zone downstream of the first temperature zone, wherein the second temperature zone is sufficient to renucleate the refractory metal material to produce a stream of nanoparticle refractory metal material; (4) separating from the stream of nanoparticle refractory metal material a discrete stream of the nanoparticle refractory metal material exhibiting a selective distribution of nanoparticle sizes; (5) exposing the optional reducing agent and the nanoparticulate refractory metal material to a third temperature zone sufficient to produce a nanoparticulate refractory metal; (6) exposing the carbon source and the nanoparticle refractory metal to a fourth temperature zone sufficient to produce the carbon material comprising SWCNTs; Including, wherein the process further comprises either depositing the nanoparticle refractory metal material on a substrate after step (4) or depositing the nanoparticle refractory metal on a substrate after step (5). A process for producing carbon materials comprising SWCNTs.

11. 1. An apparatus for producing a carbon material comprising SWCNTs, the apparatus comprising: (A) an aerosolization device for generating an aerosol stream of refractory metal material suspended in a carrier gas; (B) a temperature-controlled flow-through oven operatively connected to and downstream of the aerosolization device, the temperature-controlled flow-through oven receiving the aerosol stream of the refractory metal material and outputting a stream of nanoparticle refractory metal material during use; (C) a particle size classifier operatively connected to and downstream of said temperature-controlled flow-through furnace, said particle size classifier separating said discrete stream of nanoparticulate refractory metal material according to a selective distribution of particle sizes during use; (D) a first device for exposing an optional reducing agent and said nanoparticulate refractory metal material to a temperature sufficient to produce a nanoparticulate refractory metal; (E) a second device for exposing a carbon source and the nanoparticle refractory metal to a temperature sufficient to produce the carbon material comprising SWCNTs; wherein the apparatus further comprises a precipitator which is either operably connected to the particle size classifier and downstream of the particle size classifier, and which, in use, deposits the nanoparticle refractory metal material onto a substrate, or a precipitator which is operably connected to the first device and downstream of the first device, and which, in use, deposits the nanoparticle refractory metal material onto a substrate. An apparatus for producing carbon materials comprising SWCNTs.

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