Methods and systems for manufacturing high quality CNTS using acoustic sensors

Abstract

The present invention relates to methods and systems for manufacturing carbon nanotubes (CNTs) and other nanoparticles using acoustic sensors, and, more particularly, methods and systems for manufacturing CNTs (such as few-walled CNTs) and other nanoparticles (such as Fe nanoparticles (FeNPs)) using acoustic sensors for floating catalysts chemical vapor deposition (FCCVD).

Description

Attorney Docket No.: 072174-06101 METHODS AND SYSTEMS FOR MANUFACTURING HIGH QUALITY CNTS USING ACOUSTIC SENSORS CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] The application claims priority to U.S. Patent Appl. Serial No. 63 / 596,285, filed November 5, 2023, entitled “Methods And Systems For Manufacturing High Quality CNTs Using Acoustic Sensors,” to Glen C. Irvin, et al., which application is commonly owned by the owner of the present invention and is incorporated herein in its entirety. TECHNICAL FIELD

[0002] The present invention relates to methods and systems for manufacturing high quality carbon nanotubes (CNTs) and other nanoparticles using acoustic sensors, and, more particularly, methods and systems for manufacturing CNTs (such as few-walled CNTs) and other nanoparticles (such as Fe nanoparticles (FeNPs)) using acoustic sensors for floating catalysts chemical vapor deposition (FCCVD). GOVERNMENT INTEREST

[0003] This invention was made with government support under Grant No. DE-AR0001015, awarded by the United States Department of Energy, Advanced Research Projects Agency- Energy. The United States government has certain rights in the invention. BACKGROUND

[0004] CNTs are essentially graphene sheets rolled into hollow cylinders thereby resulting in tubules composed of sp2hybridized carbon arranged in hexagons and pentagons, which have outer diameters between 0.4 nm and 10 nm. These CNTs may be comprised of a single tube, which are termed single walled carbon nanotubes (SWCNTs) and are typically capped on each end with a hemispherical fullerene (buckyball) appropriately sized for the diameter of the SWCNT. However, these end caps may not be present due to manufacturing conditions and may be removed via processing techniques leaving uncapped tubules. SWCNTs can exist as single tubules or in aggregated form typically referred to as ropes or bundles. These ropes orAttorney Docket No.: 072174-06101 bundles may contain several or a few hundred SWCNTs aggregated through Van der Waals interactions forming triangular lattices where the tube-tube separation is approximately 3-4 Å. Ropes of SWCNTs may be composed of associated bundles of SWCNTs. CNTs may be comprised of concentric cylinders of graphene sheets and are generally termed multi-walled carbon nanotubes (MWCNTs) and the diameters can range from approximately 1 nm to 10s of nanometers. Properties of the CNTs will be dependent on the number of walls comprising the CNTs. CNTs may be comprised of mixtures of CNTs comprising 1 to 3 walls and are termed few-walled CNTs (FWCNTs). FWCNTs can have numerous commercial advantages compared to MWCNTs or SWCNTs alone.

[0005] The unique properties of CNTs (and FWCNTs) make them attractive for use in many applications. CNTs can possess high (e.g., metallic conductivities) electronic conductivities, high thermal conductivities, high modulus and tensile strength, high aspect ratio and other unique properties. Further, CNTs may be metallic, semi-metallic, or semiconducting dependent on the geometrical arrangement of the carbon atoms and the physical dimensions of the CNT.

[0006] A system has been developed to identify CNTs by using the size and spatial conformation of carbon atoms within single-wall carbon nanotubes, described below, and is currently utilized. SWCNTs are described by an index (n, m), where n and m are integers that describe how to cut a single strip of hexagonal graphite such that its edges join seamlessly when the strip is wrapped into the form of a cylinder. When n=m e.g. (n, n), the resultant tube is said to be of the “arm-chair” or (n, n) type, since when the tube is cut perpendicularly to the tube axis, only the sides of the hexagons are exposed and their pattern around the periphery of the tube edge resembles the arm and seat of an arm chair repeated n times. When m=0, the resultant tube is said to be of the “zig zag” or (n,0) type, since when the tube is cut perpendicular to the tube axis, the edge is a zig zag pattern. Where n≠m and m≠0, the resulting tube has chirality. The electronic properties are dependent on the conformation; for example, armchairAttorney Docket No.: 072174-06101 tubes are metallic and have extremely high electrical conductivity. Other tube types are semimetals or semi-conductors, depending on their conformation. CNTs have extremely high thermal conductivity and tensile strength irrespective of the chirality. The combinations of these properties confer multi-functional properties to CNTs and make them attractive for numerous commercial / industrial applications. High quality CNTs are defined by critical properties of the CNT materials including aspect ratio, CNT purity etc. High quality CNT and high quality CNT manufacturing can be used interchangeably as often the CNT material properties and CNT reaction performance are intimately related.

[0007] To achieve wide adoption as a material set in commercial markets, CNTs must be manufactured in high quality, robustly, at high production throughputs and with cost structures acceptable by commercial markets. CNT manufacturing can be conducted using various processes including arc discharge reactors, batch chemical vapor deposition reactors, laser ablation and reactors of similar designs. These reactor types are limited in the capability to produce high production volumes of quality CNTs, and thus eliminate them as viable manufacturing processes to serve mass market commercial (industrial) applications. High throughput CNT production processes are continuous and use tubular or other appropriate geometry reactor chambers which allows continuous production of CNT products and the possibility to scale the process using principles of similarity (including geometrical scaling) to produce higher production volumes. One type of high throughput CNT production process is termed floating catalyst chemical vapor deposition (FCCVD). FCCVD reactor system technology was originally developed in the 1980s for vapor grown carbon fibers [Endo 1988; Komatsu ’818 Japan Patent; Tibbetts 1989; Masuda 1992] and then adapted for carbon nanotubes in the 1990s [Cheng 1998; Nikolaev 1999]. Although FCCVD technology has been in development for approximately 40 years, the technology as applied in CNT manufacturing is not mature and many aspects of the reaction system are not known based on the fact thatAttorney Docket No.: 072174-06101 commercial systems have not been deployed and the prior art does not have detailed explanations of equipment, process mechanisms nor relationships between reactor design and high quality CNT manufacturing established. Additionally, prior art has not established design rules for process reactions and reactor systems for high quality CNT manufacturing using FCCVD technology. For CNT materials technology to reach commercial adoption of meaningful scale it will be necessary for World Class reactor systems to be developed that reproducibly produce high quality CNTs and the scale of such reactors are anticipated to need to achieve production throughputs of 3 thousand tons / year and more at World Scale (100 thousand tons / yr+). Thus, only high throughput, high quality CNT manufacturing systems will be viable to meet these demands and challenges.

[0008] FCCVD is a promising method to synthesize high throughputs of FWCNTs. As shown in FIG. 1, one version of a typical prior art FCCVD process system 110 is illustrated the vaporized organometallic catalyst precursors 115, growth promoters 116, and gaseous carbon sources are introduced using mass flow controllers 114 into hot tubular reactor chambers 111 using gases from the bank of process gases 114 which feed the mass flow controllers 114. The catalyst precursors then decompose in the reactor chamber 111 to form metal nanoparticles, which serve as catalytic decomposition points for carbon sources, and nucleation / growth sites for CNTs. Depending on the inlet streams injection configuration, the catalyst precursors may be premixed with other reactants prior to injection, or they may be introduced into the reactor through separate feed streams. [Park 2020; Lee I 2021; Vazquez-Pufleau 2024] [see also Sen 1997; Bronikowski 2001; Hou 2016; Hoecker 2016; Lee II 2021]. The manufactured CNTs are collected in a suitable collection chamber 112. The prior art FCCVD systems have no online, real time measurement and control of key process additives such as catalyst precursors and promotors which makes it impossible to control key reaction recipe ratios including S:Fe and C:Fe.Attorney Docket No.: 072174-06101

[0009] Despite seeming trivial, FCCVD reaction systems exhibit a highly-coupled, multidimensional process parameters space which makes achieving high reaction performance difficult. Small changes in the reactor chamber thermal profile, input reactant ratios, or injection configurations can meaningfully change chemical kinetics, thermodynamics, and fluid dynamics in the reactor chamber, consequently changing the resultant CNT quality, process productivity (throughput) and CNT morphology. [Bogdanova 2023; Tessonnier 2011; Grimm 2022; Gökstorp 2020; Zhang 2012; Ding 2009; Qiao 2024].

[0010] The accurate delivery of Fe containing precursors is a critical step in the manufacturing process as without a suitable Fe input stream, the CNT reaction will not proceed. Prior art processes that rely on delivering ferrocene vapor via sublimation as a catalyst precursor to generate catalytic, templating iron (Fe) nanoparticles commonly assume a stable sublimation process and use the saturation vapor pressure to estimate the mass flow of the catalyst into the reactor. [Lee I 202; Zhang 2009; Hoecker 2017; Lee 2017]. Numerous reports of sublimation equipment designs involving ferrocene as the precursor, the saturation vapor pressure is assumed based on unvalidated theoretical calculations and assumptions independent of the widely differing reported sublimation equipment and delivery methods. Many ferrocene sublimation apparatuses have been reported in the FCCVD literature, including boat-like containers placed directly in the reactor [Zhang 2009; Shibuki 2021; Yadav 2019; Khavarian 2013; Mirbagheri 2011; Yu 2011; Xie 2005; Cheng 1998], a ferrocene reservoir with flow over the free surface [Lee I 2021; Hoecker 2016], and a packed ferrocene cartridge with gas traveling through [Hussain 2018; Kaskela 2016; Oikonomou 2012; Sun 2011; Moisala 2006]. However, these different delivery systems lack detailed experimental characterizations or validations of the process effectiveness (accuracy, consistency, robustness), and differences in container properties (materials of construction, geometries, inlets / outlets, heating methods), heating conditions, and carrier gas flow rates which all can independently and / or combined canAttorney Docket No.: 072174-06101 lead to significant variations and inconsistencies in delivery rates and stability and consequently, key ratios of manufacturing precursors necessary to produce high quality CNTs at high throughputs. Other processes that rely on similar vapor delivery methods, such as the delivery of trichlorosilane (TCS) for semiconductor fabrication processes, have demonstrated that these vapor delivery systems are sensitive to temperature and pressure variabilities, leading to inconsistent manufacturing results without the use of feedback process control and proper online measurement systems. [Motamedi 1994; Constantinoiu 2020; Martin 1996].

[0011] Moreover, CNT manufacturing is achieved through the reaction of a suitable source of carbon atoms with key process additives in a reactor chamber at a set temperature. The combinations of the liberated carbon atoms from carbon sources with process additives in the reactor chamber suitably contacted when at the correct mass ratios enable production of high quality CNTs and also higher production volume rates. In prior art, key reaction additives include sulfur and Fe in order to produce CNTs. A key reaction additive, sulfur, is often used in the production of CNTs and can be referred to as a growth promoter. Current state of the art uses group 16 elements of the periodic table (S, Se, Te) as promoters. Typically, Group 16 elements are supplied using precursors such as thiophene (S), selenophene (Se) or tellurophene (Te) where the precursors are decomposed to liberate the desired Group 16 element. Sulfur can be supplied from molecular sulfur and / or through molecules containing sulfur. Fe is a catalyst for the thermocatalytic decomposition of sources of carbon atoms, for example methane, and in the production of CNTs, especially few-walled CNTs, is introduced into the reactor chamber as particles and / or formed within the reactor chamber with nanoscale dimension, typically less than 10 nm, and spheroidal morphology, preferably having aspect ratios close to 1. When the reaction additives are decomposed in the reactor chamber and the Fe catalyst nanoparticles form within the reactor chamber, it is in-situ formation of Fe catalyst nanoparticles. Also, it is possible to form Fe catalyst nanoparticles outside of the primary reactor chamber and inject FeAttorney Docket No.: 072174-06101 catalyst nanoparticles directly into the reactor chamber to effect the reaction to form CNTs, this method is called pre-formed catalysts. A wide range of catalysts and growth promoters are known by those skilled in the art and can be substituted and / or combined with Fe and / or sulfur to produce CNTs. Both the catalyst precursors and promoter precursors can be delivered to the reactor chamber in a gaseous / vapor state. These key additives can be vaporized in any number of suitable methods including but not limited to sublimation, bubbling / evaporation, flash vaporization or combinations of these and other methods.

[0012] Sulfur is known to influence the production of Fe catalyst nanoparticles and the ratio of S:Fe can be an important process factor that impacts the production of CNTs. Weller 2019 disclosed a summary taken from the available literature of various S:Fe ratios and the types of CNTs that were produced using the specific ratios. In Weller 2019, the S:Fe ratios reported were not accurately quantified, or controlled and the reported results are only qualitatively mapped to number of walls within a CNT. Hence, the prior art, including Weller 2019, did not provide accurate data correlating S:Fe ratio to key CNT manufactured materials characteristics for quality determination nor synthesis process performance. In fact, there were fluctuations and systematic errors that rendered it is not possible to correlate synthesis process ratios such as S:Fe since the prior art has no manufacturing methods to measure and control S and Fe mass flow rates in real time. Such processes have import to determine commercial viability of a manufacturing process and the CNT materials it produces.

[0013] Another ratio that can have importance in CNT manufacturing performance is C:Fe ratio. The ratio of the carbon atoms to the Fe in nanoparticle form can greatly influence the CNT production, quality, and cost. The Fe nanoparticles will also be characterized by the mean diameter, degree of polydispersity, dominant morphology, and number density in the critical reaction volume. The ratio of C:Fe in the reactor chamber, in the reaction zone, where it is uniform and continuously supplied at the setpoint ratio, accurately, will generally determineAttorney Docket No.: 072174-06101 the properties of the CNTs. CNT Properties such as the diameter, aspect ratio and chirality can be controlled through accurate, controlled, continuously reproducible C:Fe ratios in the reactor chamber. Temperature and Pressure Sensitivity Analysis on Ferrocene Sublimation Process

[0014] In the prior art, no methods are disclosed to measure, monitor and control key process reaction additives on CNT manufacturing systems, in real time. This is a disadvantage that does not enable high quality CNT manufacturing cost effectively. Instead of actually conducting measurements of key process additives mass flow rates / concentrations in reaction streams such as Fe and Sulfur precursors, the prior art relies upon a theoretical equation to estimate or assume key process additive mass flow rates. The theoretical equation has not been verified nor validated with actual measurements which makes it difficult to impossible to know actual process recipe setpoints (e.g., key process ratios) and the concentrations of key reaction species in the reactor chamber as a function of time, all of which are important to manufacture high quality, high throughput CNTs.

[0015] Fulem 2013 discloses the typical theoretical equation used to estimate the vapor pressure of a key reaction additive within a delivery chamber based on an ideal vapor-solid equilibrium and using Dalton’s law of partial pressure to estimate or assume key reaction values (e.g. precursor mass flow rates). The estimated or assumed vapor pressure data is utilized to calculate mass flow rates of key reaction additives and conceptually, the ratios between key reaction additives. It is well known in the art that numerous process variabilities impact setpoints such as temperature and pressure and it is not uncommon for a process to realize changes in temperature, for example, up to several degrees during operation and pressure variability from 0.5 psi (3.45 kPa) to 2.5 psi (17.24 kPa).

[0016] In the equation disclosed by Fulem 2013, which is generally used in the CNT FCCVD prior art, it does not account for real operation scenarios in sublimators and bubblers as well asAttorney Docket No.: 072174-06101 reactor systems. For instance, these processes are undergoing phases changes which require energy to vaporize the precursors thus lowering localized temperatures within the delivery vessels by as much as 2 – 5 degrees. Additionally, there is no accounting for real pressure changes and pressure drops during operation of the sublimators / bubblers. Mass transfer from delivery vessels to the reaction chamber is a dynamic process which invokes changes to solid materials surface areas thereby changing rates of sublimation (mass flow rates) and liquid level in bubbler vessels thereby changing rates of evaporation (mass flow rates). Also, mass transfer rates may be variable due to channeling patterns or other changes to the gas-to-solid contact areas that develop inside the cartridge as the hot carrier gas flows through in each experiment. [Kirillov 2005; Schildhauer 2012; Nguyen 1997]

[0017] To understand and illustrate the effect of (1) inherent process variabilities (2) use of a theoretical equation to assume process values on sublimation conditions for ferrocene vapor delivery rates, the temperature and pressure sensitivities of the ferrocene sublimation process and thiophene bubbler process at a given temperature and pressure were examined using the theoretical equation method of prior art. The ferrocene pressure analysis at 333 K is shown in FIG.2C (with plots 221-223 for ±0.5 kPa, ±2.5 kPa, and ±5.0 kPa, respectively, with vertical dashed line 224 showing P = 101.325 kPa). The thiophene pressure analysis at 267 K is shown in FIG.2A (with plots 201-203 for ±0.5 kPa, ±2.5 kPa, and ±5.0 kPa, respectively, with vertical dashed line 204 showing P = 101.325 kPa).

[0018] Temperature variations strongly influence the thiophene mass transfer rate while maintaining a constant bubbler vessel pressure, as shown in FIG.2B (with plots 211-213 for ±1 K, ±3 K, and ±5 K, respectively, with vertical dashed line 214 showing T = 267 K (-6 °C), a typical sublimation condition in the prior art. Also, temperature variations strongly influence the ferrocene mass transfer rate while maintaining a constant sublimation vessel pressure, as shown in FIG.2D (with plots 231-233 for ±1 K, ±3 K, and ±5 K, respectively, with verticalAttorney Docket No.: 072174-06101 dashed line 234 showing T = 333 K (60 °C), a typical sublimation condition in the prior art). It is clear that the prior art methodology for designing the CNT FCCVD process is (1) unreliable based on these simulations (2) susceptible to process variability inherent in all systems (3) run without control feedback methods to correct for such gross errors in key process additives mass flow rates which are critical process design parameters to realize high quality, high productivity CNT manufacturing.

[0019] At the typical ferrocene sublimation temperature for the FCCVD synthesis process of 333 K (60 °C), a ±1 K temperature perturbation can potentially change the mass flow rate by an average of + / - 8% around the setpoint and larger ±5 K temperature variations can vary the mass flow rate by up to an average of + / - 45%. It is also clear from Fig 5C, 5D. Temperature variations that persist during extended experimental periods can potentially lead to significant discrepancies in the overall desired amount of catalyst used, and importantly in the key process ratios with the carbon atoms and growth promoters. The temperature variation in a sublimation system depends on a combination of the heating and the control methods used, and the associated tuning techniques. As most systems are likely to experience some variability, there is import of, and significant benefits to, implementing a monitoring system to ensure a consistent ferrocene vapor mass flow rate.

[0020] Kauppinen ’130 PCT Application disclosed methods for CNT manufacturing using a continuous manufacturing process. However, there are no process control devices suitable to ensure key process additives are delivered to the reactor chamber accurately and that specific process ratios, such as S:Fe, can be controlled to continuously provide high quality CNTs at high production volumes.

[0021] Predtechenskiy ’316 Application disclosed methods to manufacture SWCNTs at high production volumes using continuous reactor systems. However, it does not disclose any process control methods and / or devices suitable to ensure key process additives are deliveredAttorney Docket No.: 072174-06101 to the reactor chamber accurately and that specific ratios, such as C:Fe and / or S:Fe, can be controlled to continuously provide high quality CNTs at high production volumes.

[0022] Thus, while the art discloses a wide variety of CNT manufacturing processes, the stringent requirements of high quality, reproducible production at production volumes necessary for mass market commercial / industrial applications is extremely difficult to attain with processes described in the prior art. Thus, there remains a critical need for controlled CNT manufacturing processes that can produce high quality CNTs, at high production volumes with competitive cost structures. SUMMARY OF INVENTION

[0023] The present invention relates to methods and systems for manufacturing high quality carbon nanotubes (CNTs) and other nanoparticles using acoustic sensors, and, more particularly, methods and systems for manufacturing CNTs (such as few-walled CNTs) and other nanoparticles (such FeNPs) using acoustic sensors for floating catalysts chemical vapor deposition (FCCVD) reaction systems.

[0024] In particular, the invention provides a CNT manufacturing system including an acoustic sensor wherein the acoustic sensor is disposed between a delivery system for key CNT reaction additives and the reactor chamber wherein said acoustic sensor accurately measures real time stream compositions of key reaction additives mass flow rates and enables accurate control of said key reaction additives using process recipe setpoints and wherein accurately controlled mass ratios of certain key reaction additives enables controlled, reproducible high quality carbon nanotube manufacturing.

[0025] In general embodiments, the present invention is directed to a carbon nanotube manufacturing system. The carbon nanotube manufacturing system can include a reactor chamber configured to facilitate the production of carbon nanotubes. The carbon nanotube manufacturing system can include a delivery system configured to supply carbon nanotubeAttorney Docket No.: 072174-06101 reaction additives to the reactor chamber. The carbon nanotube manufacturing system can include an acoustic sensor disposed between the delivery system and the reactor chamber. The acoustic sensor can be configured to measure real-time stream compositions of the reaction additives. The acoustic sensor can be configured to determine mass flow rates of the reaction additives. The carbon nanotube manufacturing system can include a control unit communicatively coupled to the acoustic sensor and the delivery system. The control unit can be configured to receive measurements from the acoustic sensor. The control unit can be configured to adjust the mass flow rates of the reaction additives based on the received measurements to conform to process recipe setpoints. The control unit can be configured to control the mass ratios of the reaction additives to enable the production of carbon nanotubes with controlled, reproducible, and high-quality characteristics. The control unit can be configured to control the mass ratios of the reaction additives based on measured data received on the characteristics of the CNTs manufactured to enable consistent production of CNTs with controlled, reproducible, and high-quality characteristics.

[0026] In general embodiments, the present invention is directed to a method for manufacturing carbon nanotubes using a system with real-time control of reaction additives. The method can include providing a reactor chamber suitable for the production of carbon nanotubes. The method can include delivering carbon nanotube reaction additives to the reactor chamber using a delivery system. The method can include measuring real-time stream compositions and mass flow rates of the carbon nanotube reaction additives using an acoustic sensor disposed between the delivery system and the reactor chamber. The method can include communicating the measurements from the acoustic sensor to a control unit. The method can include adjusting, by the control unit, the mass flow rates of the carbon nanotube reaction additives based on the measurements. The method can include controlling, by the control unit, the mass ratios of the carbon nanotube reaction additives based on the adjustments to enableAttorney Docket No.: 072174-06101 the production of carbon nanotubes.

[0027] In further general embodiments, the present invention is directed to a system that includes a reactor chamber configured to facilitate the production of nanoparticles. The system further includes a delivery system configured to supply nanoparticle reaction additives to the reactor chamber. The system further includes an acoustic sensor disposed between the delivery system and the reactor chamber. The acoustic sensor is configured to measure real-time stream compositions of the reaction additives. The acoustic sensor is further configured to determine mass flow rates of the reaction additives. The system further includes a control unit communicatively coupled to the acoustic sensor and the delivery system. The control unit is configured to receive measurements from the acoustic sensor. The control unit is further configured to adjust the mass flow rates of the reaction additives based on the received measurements to conform to process recipe setpoints. The control unit is further configured to control the mass ratios of the reaction additives to enable the production of the nanoparticles.

[0028] Implementations of the invention can include one or more of the following features:

[0029] The nanoparticles can be nanotubes.

[0030] The nanoparticles can be carbon nanotubes (CNTs).

[0031] The nanoparticles can be few-walled carbon nanotubes (FWCNTs).

[0032] The nanoparticles can be Fe nanoparticles.

[0033] The can be a floating catalysts chemical vapor deposition (FCCVD) manufacturing system. The reactor chamber can be a FCCVD reactor chamber.

[0034] The system can include a bank of process gases.

[0035] The bank of process gases can include one or more process gases selected from the group consisting of inert gases and carbon atom source gases.

[0036] The bank of process gases can include one or more process gases selected from the group consisting of Ar, N2, H2, He, and CH4.Attorney Docket No.: 072174-06101

[0037] The delivery system can be configured to supply a metallic nanoparticle reaction additive to the reactor chamber. The system can include a metal delivery source for supplying the metallic nanoparticle reaction additive. The metallic nanoparticle reactive additive includes a metal atom.

[0038] The metal atom can be Fe.

[0039] The metallic nanoparticle reaction additive can be ferrocene.

[0040] The metallic nanoparticle reaction additive can be a metallic nanoparticle reaction additive used for carbon nanotube manufacturing.

[0041] The metal delivery source can include a sublimater.

[0042] The sublimater can include a ferrocene cartridge.

[0043] The delivery system can be configured to supply a sulfur nanoparticle reaction additive source to the reactor chamber. The system can include a sulfur delivery source for supplying the sulfur nanoparticle reaction additive source. The sulfur nanoparticle reactive additive source includes sulfur.

[0044] The sulfur nanoparticle reactive additive can be a dimer, oligomer, and / or other type of particle.

[0045] The sulfur nanoparticle reaction additive source can be thiophene.

[0046] The sulfur delivery source can include a source bubbler.

[0047] The source bubbler can be a thiophene bubbler.

[0048] The acoustic sensor can be an acoustic gas sensor.

[0049] The acoustic sensor can be a binary acoustic gas sensor.

[0050] The delivery system can configured to supply a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive includes a metal atom (M). The delivery system can be configured to supply a sulfur nanoparticle reaction additive to the reactor chamber. The acoustic sensor can be operable to measure the ratio ofAttorney Docket No.: 072174-06101 S:M to control the quality of the nanoparticles manufactured by the system.

[0051] The bank of process gases can include at least one carbon-containing gas.

[0052] The at least one carbon-containing gas can be CH4.

[0053] The delivery system can be configured to supply a sulfur nanoparticle reaction additive to the reactor chamber. The bank of process gases can include at least one carbon-containing gas. The acoustic sensor can be operable to measure the ratio of C:S to control the quality of the nanoparticles manufactured by the system.

[0054] The delivery system can be configured to supply a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive includes a metal atom (M). The bank of process gases can include at least one carbon-containing gas. The acoustic sensor can be operable to measure the ratio of C:M to control the quality of the nanoparticles manufactured by the system.

[0055] The delivery system can configured to supply a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive comprises a metal atom (M). The delivery system can be configured to supply a sulfur nanoparticle reaction additive to the reactor chamber. The bank of process gases can include at least one carbon- containing gas. The acoustic sensor can be operable to measure at least two of (i) the ratio of S:M, (ii) the ratio of C:S, and (iii) the ratio of C:M, to control the quality of the nanoparticles manufactured by the system.

[0056] The ratio of S:M can be set at a predetermined S:M ratio and the system can be operable to maintain the ratio of the S:M at the S:M predetermined ratio ± 10%.

[0057] The ratio of C:M can be set at a predetermined C:M ratio and the system can be operable to maintain the ratio of the C:M at the C:M predetermined ratio ± 10%.

[0058] The ratio of C:S can be set at a predetermined C:S ratio and the system can be operable to maintain the ratio of the C:S at the C:S predetermined ratio ± 10%.Attorney Docket No.: 072174-06101

[0059] The system can maintain one or more of the predetermined ratios ± 5%.

[0060] The system can maintain one or more of the predetermined ratios ± 1%.

[0061] The system can maintain one or more of the predetermined ratios ± 0.5%.

[0062] The system can maintain one or more of the predetermined ratios ± 0.1%.

[0063] The metal atom (M) can be Fe.

[0064] In further general embodiments, the present invention is directed to a method for manufacturing nanoparticles using a system with real-time control of reaction additives. The method includes providing a reactor chamber suitable for the production of nanoparticles. The method further includes delivering nanoparticle reaction additives to the reactor chamber using a delivery system. The method further includes measuring real-time stream compositions and mass flow rates of the nanoparticle reaction additives using an acoustic sensor disposed between the delivery system and the reactor chamber. The method further includes communicating the measurements from the acoustic sensor to a control unit. The method further includes adjusting, by the control unit, the mass flow rates of the nanoparticle reaction additives based on the measurements. The method further includes controlling, by the control unit, the mass ratios of the nanoparticle reaction additives based on the adjustments to enable the production of the nanoparticles.

[0065] Implementations of the invention can include one or more of the following features:

[0066] The nanoparticles can be nanotubes.

[0067] The nanoparticles can be carbon nanotubes (CNTs).

[0068] The nanoparticles can be few-walled carbon nanotubes (FWCNTs).

[0069] The nanoparticles can be Fe nanoparticles.

[0070] The method can be a floating catalysts chemical vapor deposition (FCCVD) manufacturing method. The reactor chamber can be a FCCVD reactor chamber.

[0071] The system can include a bank of process gases.Attorney Docket No.: 072174-06101

[0072] The bank of process gases can include one or more process gases selected from the group consisting of inert gases and carbon atom source gases.

[0073] The bank of process gases can include one or more process gases selected from the group consisting of Ar, N2, H2, He, CH4.

[0074] The delivery system can deliver a metallic nanoparticle reaction additive to the reactor chamber. The system can include a metal delivery source for supplying the metallic nanoparticle reaction additive. The metallic nanoparticle reactive additive includes a metal atom.

[0075] The metal atom can be Fe.

[0076] The Fe nanoparticle reaction additive can be ferrocene.

[0077] The metallic nanoparticle reaction additive can be a metallic nanoparticle reaction additive used for carbon nanotube manufacturing.

[0078] The metal delivery source can include a sublimater.

[0079] The sublimater can include a ferrocene cartridge.

[0080] The delivery system can deliver a sulfur nanoparticle reaction additive source to the reactor chamber. The system can include a sulfur delivery source for supplying the sulfur nanoparticle reaction additive source. The sulfur nanoparticle reactive additive source includes sulfur.

[0081] The sulfur nanoparticle reactive additive can be a dimer, oligomer, and / or other type of particle.

[0082] The sulfur nanoparticle reaction additive can be thiophene.

[0083] The sulfur delivery source can include a source bubbler.

[0084] The source bubbler can be a thiophene bubbler.

[0085] The acoustic sensor can be an acoustic gas sensor.

[0086] The acoustic sensor can be a binary acoustic gas sensor.Attorney Docket No.: 072174-06101

[0087] The delivery system can deliver a metallic nanoparticle reaction additive to the reactor chamber wherein the metallic nanoparticle reactive additive includes a metal atom (M). The delivery system can deliver a sulfur nanoparticle reaction additive to the reactor chamber. The acoustic sensor can measure the ratio of S:M. The quality of the nanoparticles manufactured by the system can be controlled by controlling the ratio of S:M.

[0088] The bank of process gases can include at least one carbon-containing gas.

[0089] The at least one carbon-containing gas can be CH4.

[0090] The delivery system can deliver sulfur nanoparticle reaction additive to the reactor chamber. The bank of process gases can include at least one carbon-containing gas. The system can delivers at least one carbon-containing gas to the reactor chamber. The acoustic sensor can measure the ratio of C:S. The quality of the nanoparticles manufactured by the system can be controlled by controlling the ratio of C:S.

[0091] The delivery system can deliver a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive includes a metal atom (M). The bank of process gases can include at least one carbon-containing gas. The system can deliver at least one carbon-containing gas to the reactor chamber. The acoustic sensor can measure the ratio of C:M. The quality of the nanoparticles manufactured by the system can be controlled by controlling the ratio of C:M.

[0092] The delivery system can deliver a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive includes a metal atom (M). The delivery system can deliver sulfur nanoparticle reaction additive to the reactor chamber. The bank of process gases can include at least one carbon-containing gas. The system can deliver at least one carbon-containing gas to the reactor chamber. The acoustic sensor can measure at two of (i) the ratio of S:M, (ii) the ratio of C:S, and (iii) the ratio of C:M. The quality of the nanoparticles manufactured by the system can be controlled by controlling at least two of (i)Attorney Docket No.: 072174-06101 the ratio of S:M, (ii) the ratio of C:S, and (iii) the ratio of C:M.

[0093] The method can further include selecting a predetermined S:M ratio. The method can further include utilizing the system to maintain the ratio of the S:M at the S:M predetermined ratio ± 10% while manufacturing the nanoparticles.

[0094] The method can further include selecting a predetermined C:M ratio. The method can further include utilizing the system to maintain the ratio of the C:M at the C:M predetermined ratio ± 10% while manufacturing the nanoparticles.

[0095] The method can further include selecting a predetermined C:S ratio. The method can further include utilizing the system to maintain the ratio of the C:S at the C:S predetermined ratio ± 10% while manufacturing the nanoparticles.

[0096] The method can further include maintaining one or more of the predetermined ratios ± 5%.

[0097] The method can further include maintaining one or more of the predetermined ratios ± 1%.

[0098] The method can further include maintaining one or more of the predetermined ratios ± 0.5%.

[0099] The method can further include maintaining one or more of the predetermined ratios ± 0.1%.

[0100] The metal atom (M) can be Fe.

[0101] The method is performed using a system selected from the group consisting of the above-described systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] FIG.1 shows the state of the art CNT production using a typical FCCVD reactor system used in prior art.

[0103] FIG. 2 shows errors in mass flow rates of key reaction additives using prior artAttorney Docket No.: 072174-06101 estimating methods for CNT manufacturing. These figures indicate that prior art capability to control key process ratios is very limited to non-existent using prior art technology. The errors are shown for temperature and pressure sensitivity analyses on ferrocene sublimation and thiophene bubbling evaporating mass transfer methods. FIG.2A shows pressure sensitivity of the ferrocene vapor pressure at 333 K (60 °C). FIG.2B shows temperature sensitivity of the ferrocene vapor pressure during the sublimation process at atmospheric pressure. FIG. 2C shows comparison of the total collected Fe catalyst amount obtained from the acoustic sensor against amount derived from UV-Vis spectrophotometer concentration measurements across 15 offline setup experiments, which conducted under similar sublimation temperatures (333- 343 K) and system pressures (103.4 kPa). Error bars represent the standard deviation of all acoustic sensor molar concentration readings during the experiment. FIG.2D shows real-time ferrocene vapor mass flow rate fluctuations and deviations from the ideal vapor pressure curve calculation at three different conditions.

[0104] FIGS.3A-3B show schematic diagrams of the instant invention showing a section of a CNT manufacturing system having, respectively, horizontally and vertically oriented with respect to gravity, floating catalysts chemical vapor deposition (FCCVD) reactor setups.

[0105] FIG.4 illustrates the errors in ferrocene precursor mass flow rate of the prior art using the acoustic sensor for the Instant Invention to measure and monitor the real time mass flow rate.

[0106] FIGS.5 demonstrates the prior art average mass flow rate error when compared with embodiments of the present invention clearly showing these embodiments of the present invention confer superior performance to maintain key precursor mass flow rates and by extension, key process ratios.

[0107] FIG. 6 shows a process map constructed using the CNT FCCVD system and method of the present invention relating input S / Fe key process ratio to solid carbon conversion rate.Attorney Docket No.: 072174-06101

[0108] FIG.7 shows a process map constructed using the CNT FCCVD system and method of the present invention relating input S / Fe key process ratio to solid carbon production rate, an important process metric for CNT manufacturing quality and performance.

[0109] FIG.8 shows a process map constructed using the CNT FCCVD system and method of the present invention relating S / Fe ratios (ferrocene and thiophene mass flow rate ratios) with CNT average aspect ratios. DETAILED DESCRIPTION

[0110] The present invention provides numerous advantages over the existing prior art. The present invention relates to methods and systems for manufacturing high quality carbon nanotubes (CNTs) and other nanoparticles using acoustic sensors, and, more particularly, methods and systems for manufacturing CNTs (such as few-walled CNTs) and other nanoparticles (such as Fe nanoparticles (FeNPs)) using acoustic sensors for floating catalysts chemical vapor deposition (FCCVD).

[0111] The methods and systems employs non-invasive acoustic sensors that accurately measure key process controlling reaction additives enabling specific, accurate additives ratios known to enable, consistent and controlled high quality CNT production. The acoustic gas analyzer is incorporated inline with the ferrocene sublimation apparatus to highlight the limitations of the saturated vapor assumption for estimating the ferrocene vapor mass flow rate. This approach enables the measurement and analysis of catalyst mass flow rate, the mass flow rate variability and these parameters impact on FWCNT synthesis performance. Integrating the acoustic sensor into a feedback system can successfully counteract inter-and intra-run variability in iron (Fe) catalyst delivery in these ferrocene sublimation-based FCCVD systems.

[0112] Use of acoustic sensors to manufacture high quality CNTs where the focus is the quantitative control of the input molar S:Fe ratio by controlling the respective mass flowrates ofAttorney Docket No.: 072174-06101 sulfur and iron or similar process additives as we have found that to be highly critical for effective, high quality CNT manufacturing. After approximately 40 years in development, the existing literature has no quantitative control methodologies and no PID control methodologies for controlling the S:Fe ratio and thereby the CNT manufacturing process is not controlled, often showing high variability in the product characteristics and quality. This method enables the accurate control of these molecules and thereby provides a method to control their ratio to achieve high quality CNT formation as well as higher productivities. An acoustic sensor is placed inline with the process chemicals of interest, Sulfur source and iron source in this case, and measures the concentration (mass flow rates) of such chemicals, respectively and independently, when in a binary gas / vapor stream. The sulfur and iron start in some molecular format (thiophene and ferrocene in this case).

[0113] As the sulfur and iron containing molecules enter the reactor chamber, they will be decomposed through thermal energy means liberating the sulfur and iron atoms. The input concentrations of S and Fe have import for the production of Fe nanoparticles (FeNPs). Process setpoints for the specific chemicals can be placed in a controlled logic format and / or via manual adjustment of setpoints and the data provided by the sensor will control the chemical compositions in the streams to the desired setpoint. Using process knowledge and experimental investigations, the appropriate ratio of S:Fe is determined and necessary that it is maintained close to the setpoint.

[0114] Surprisingly, it has been found that the acoustic sensor can accurately measure the ferrocene vapor concentration in the gas mixture to quantify and monitor the input delivery rate and enable control of key process reaction ratios.. Additionally, the acoustic sensor may be used to measure Fe nanoparticles mass flow rates in order to accurately set ratios between Fe and C atoms key process ratios. Fe nanoparticles may be supplied to the reactor in any of the known, controllable, cost effective methods known in the art, such as plasma basedAttorney Docket No.: 072174-06101 nanoparticle formation such that the Fe nanoparticles are pre-formed prior to entering the reactor chamber. FCCVD System With Acoustic Sensor

[0115] The instant invention provides controllable, reproducible CNT manufacturing systems which can produce high quality CNTs at high production rates. The present invention allows for high quality CNT manufacturing methods at sufficiently high production volumes thereby reducing complexity and cost of the manufacturing method enabling wide adoption of these high quality CNTs in mass market commercial applications.

[0116] FIGS. 3A-3B show one embodiment of a FCCVD CNT manufacturing system incorporating the instant invention as shown in the schematics outlines the system for reaction additives delivery equipment inline with acoustic sensors and connected to a computer controlled logic controller to enable the accurate control of key reaction additives mass flow rates and delivery into the reactor chamber. As shown in the schematics of FIGS.3A-3B, the current invention displays a section of a CNT manufacturing processes 310 and 330 (shown in FIGS.3A-3B, respectively) that includes a reactor 311 (horizontal in FIG.3A and vertical in FIG.3B) that is heated by suitable means, a collection chamber 312 for product that can be removed in process, a suitable abatement system 317, a bank of process gases 314, that are precisely delivered by mass flow controllers, key process additives (a) Fe delivery source sublimater containing ferrocene 315 (such as a ferrocene cartridge) and (b) a sulfur delivery source bubbler containing thiophene 316 (such as thiophene bubbler), which are both temperature controlled using a temperature control system 321, and acoustic sensors 318 that are in communication 313 with a computer controlled logic controller 319 that is also in communication 320 with the bank of mass flow controllers 314. The system can also have a catalyst purge 322. Moreover, reactor 311 can have separate thermal controlled zones, such as zones 311a-311c, as shown in FIG. 3B. Any suitable acoustic sensor may be used including the BGA244 binary gas sensor, Piezocon Vapor Concentration sensor or other similarAttorney Docket No.: 072174-06101 technologies known to those skilled in the art. Altogether, this CNT manufacturing process can accurately control the key process additives wherein key process ratios such as S:Fe and C:Fe can controllably produce high quality CNTs, reproducibly and at high production rates and volumes. Use of Acoustic Sensor to Assess Prior Art Key Precursor Delivery Efficacy

[0117] The acoustic sensor of the instant invention was used to measure, monitor and assess the mass transfer efficacy of the process for key precursor additives mass transfer which is a critical step in CNT manufacturing. In FIG.4, data for three experiments, 431, 432, and 433 are shown as a function of manufacturing process time. (Experiments 431, 432, and 433 are for 333 ± 0.5K with 1400 sccm Ar, 343 ±1K with 1400 sccm N2, and 343 ±2 K with 1000 sccm N2, respectively). Use of the acoustic sensor enabled a previously unavailable capability to measure real time key precursor mass transfer rates. The conditions tested in 431, 432, and 433 are representative of prior art temperature and carrier gas flow rates using in CNT manufacturing. The acoustic sensor was calibrated and validated using a test setup where the mass transfer from the sublimation vessel is transferred into a collection vessel containing a suitable solvent. The amount of ferrocene transferred into the collection vessel during the manufacturing process time is measured using ultraviolet-visible spectroscopy thereby measuring the concentration delivered in the total time. That value measured by the UV-VIS method is compared with the acoustic sensor which was found to agree within 2% - 4% on average providing confidence and validation of the acoustic sensor measurement method. Comparative Example 1

[0118] Data for comparative example 1 experiment was conducted to test the efficacy of the state of the art saturation vapor pressure curve estimate from the literature as discussed in the Background herein. Ferrocene powder was loaded into a delivery vessel similar to that shown in FIGS.3A and 3B. The vessel was connected to a carrier gas, N2, and the outlet of the deliveryAttorney Docket No.: 072174-06101 vessel was connected inline with the acoustic sensor. The acoustic sensor was connected to a computer in order to receive and process data as well as setup conditions for the sensor. The sublimation vessel was set to a temperature of 333 K and the carrier gas flow rate was set to 1400 sccm using a mass flow controller. Valves to and from the delivery vessel were opened so that mass transfer from the vessel through the acoustic sensor could occur and measurements of the real time ferrocene precursor mass flow could be conducted. The data in FIG. 4, experiment 431 were logged. The data is plotted such that using the prior art method to estimate the ferrocene precursor mass flow rate, the offset of the actual, measured value using the acoustic sensor is presented on the graph. In experiment 431 it is seen that from the beginning of the experiment the estimated value is off by at least 10% and while monitoring the process, the data is continuously varying up to 20%. These large errors make it impossible for the prior art to confidently, consistently, reproducibly establish key process ratios needed in manufacturing high quality CNTs cost effectively. Comparative Example 2

[0119] Comparative example 2 was conducted in the same apparatus as Comparative Example 1. The sublimation vessel was set to a temperature of 343 K and the carrier gas flow rate was set to 1400 sccm using a mass flow controller. The data are presented in FIG.4, experiment 432. In this experiment, it is shown that the deviation offset from the prior art predicted methodology for ferrocene mass flow rate is 20% at the beginning of the experiment and the process never corrects to achieve the desired setpoint. Throughout the experiment 432, the error in ferrocoene mass flow rate is approximately 20%, a significant error. These large errors make it impossible for the prior art to confidently, consistently, reproducibly establish key process ratios needed in manufacturing high quality CNTs cost effectively. Comparative Example 3

[0120] Comparative example 3 was conducted in the same apparatus as Comparative ExampleAttorney Docket No.: 072174-06101 1. The sublimation vessel was set to a temperature of 343 K and the carrier gas flow rate was set to 1000 sccm using a mass flow controller. The data are presented in FIG.4, experiment 433. In this experiment 433, it is shown that the deviation offset from the prior art predicted methodology for ferrocene mass flow rate is 38% at the beginning of the experiment and the process never corrects to achieve the desired setpoint. Throughout the experiment, the error in ferrocoene mass flow rate is approximately 50%, a significant error with errors approaching 60%. These are very large errors which make it impossible for CNT FCCVD practitioners of the prior art to confidently, consistently, reproducibly establish key process ratios needed in manufacturing high quality CNTs cost effectively. In context, Comparative Examples 1, 2, and 3 demonstrate the prior art technology (assuming mass flow rates based on theoretical equations) to estimate key process additives mass flow rates (and thereby key process ratios) is grossly inadequate and does not enable CNT FCCVD systems requisite for high quality, competitive cost manufacturing. As will be illustrated in FIG. 5 and 7 below, uncontrolled variability and changes in mass flow rates during manufacturing such as shown in FIG. 4 can shift a CNT manufacturing process out of the desired operating window, very easily. The prior art does not teach the critical relationship between S:Fe key process ratios and high quality CNT manufacturing cost effectively nor does it teach methods to measure such key process additives accurately, real time enabling control of key process ratios. Comparative Example 4

[0121] Using a setup similar to FIG.3B, experiments were conducted to measure the average ferrocene input mass flow rate during 30 min to 60 min test time. The acoustic sensor of the present invention is used to measure and monitor the ferrocene precursor transfer process. Ferrocene powder was loaded into a delivery vessel similar to that shown in FIG. 3B. The vessel was connected to a carrier gas, N2, and the outlet of the delivery vessel was connectedAttorney Docket No.: 072174-06101 inline with the acoustic sensor. The acoustic sensor was connected to a computer in order to receive and process data real time as well as setup conditions for the sensor. The sublimation vessel was set to a temperature of 333 K and the N2carrier gas flow rate was set to 1400 sccm using a mass flow controller. The ferrocene mass flow rate setpoint was set at 40 mg / hr. Valves to and from the delivery vessel were opened so that mass transfer from the vessel through the acoustic sensor could occur and measurements of the real time ferrocene precursor mass flow could be conducted.

[0122] The data in FIG.5, 511 were logged and compiled as an average over the test time. The data is plotted such that the ferrocene precursor mass flow rate difference from the setpoint as measured by the acoustic sensor is presented on the graph. A total of 4 tests were completed. Data in 511 show that the error from the setpoint ranges from approximately 4% to 30% in the different experiments. The error in these experiments are similar in range to data presented in FIGS. 2 and 4 and such error ranges are unacceptable since the process can not consistently and accurately maintain the critical setpoints and thus key process ratios needed to produce high quality, cost competitive CNTs. Present Invention Example 1

[0123] Using the setup of Comparative Example 4, experiments were conducted to measure the average ferrocene input mass flow rate during 30 min to 60 min test time. The acoustic sensor of the instant invention is used to measure and monitor the ferrocene precursor transfer process. Additionally, per the Instant Invention, a basic control scheme of controlling the ferrocene bath temperature to reduce error offset from the setpoint as shown in the data reported from the acoustic sensor. Ferrocene powder was loaded into a delivery vessel similar to that shown in FIG.3B. The vessel was connected to a carrier gas, N2, and the outlet of the delivery vessel was connected inline with the acoustic sensor. The acoustic sensor was connected to a computer in order to receive and process data real time as well as setup conditions for theAttorney Docket No.: 072174-06101 sensor. The sublimation vessel was set to a temperature of 333 K and the N2carrier gas flow rate was set to 1400 sccm using a mass flow controller. The ferrocene mass flow rate setpoint was set at 40 mg / hr. During the test period, a control scheme was implemented to adjust the ferrocene bath temperature based on feedback from the acoustic sensor measurement of ferrocene mass flow rate. The data in FIG. 5, 512 were logged and compiled as an average over the test time. The data is plotted such that the ferrocene precursor mass flow rate difference from the setpoint as measured by the acoustic sensor is presented on the graph. A total of 15 tests were completed. Using the acoustic sensor with a basic control scheme resulted in ferrocene mass flow rate errors of + / - 5 from the setpoint value, a significant improvement over the prior art data shown in FIG.5, 511, and FIG.4. Present Invention Example 2

[0124] Using the setup of Comparative Example 4, experiments were conducted to measure the average ferrocene input mass flow rate during 30 min to 60 min test time. The acoustic sensor of the instant invention is used to measure and monitor the ferrocene precursor transfer process.

[0125] Additionally, per the present invention, a P-type control scheme of controlling the ferrocene mass flow rate was implemented to reduce error of the offset from the setpoint as shown in the data reported from the acoustic sensor. For these reasons, a proportional (P) feedback control system was developed based on the acoustic sensor and two MFCs. Within this framework, the carrier gas flow rate through the ferrocene cartridge serves as the key adjustable variable, providing corrective actions to rectify any discrepancies that deviate ±5% from the desired setpoint. The supplementary gas flow through the second MFC ensured a constant total flow reached the acoustic sensor and any downstream equipment to minimize the influence of other sources of process disturbances or transients. It is understood by those skilled in the art that multiple control methodologies may be designed and employed to accuratelyAttorney Docket No.: 072174-06101 control key process additives and the key process ratios necessary for high quality, cost effective CNT manufacturing using methods of the present invention,

[0126] Ferrocene powder was loaded into a delivery vessel similar to that shown in FIG.3B. The vessel was connected to a carrier gas, N2, and the outlet of the delivery vessel was connected inline with the acoustic sensor. The acoustic sensor was connected to a computer in order to receive and process data real time as well as setup conditions for the sensor. The computer also implemented the P-type control algorithm to control the ferrocene mass flow rate to the setpoint value. The sublimation vessel was set to a temperature of 333 K and the N2carrier gas flow rate was set to 1400 sccm using a mass flow controller. The ferrocene mass flow rate setpoint was set at 40 mg / hr. During the test period, a P-type control scheme was implemented to adjust the ferrocene mass flow rate based on feedback from the acoustic sensor measurement of ferrocene mass flow rate. The data in FIG.5, 513 were logged and compiled as an average over the test time. The data is plotted such that the ferrocene precursor mass flow rate difference from the setpoint as measured by the acoustic sensor is presented on the graph. A total of 3 tests were completed. Using the acoustic sensor with a P-type control scheme resulted in ferrocene mass flow rate errors of + / - 2 from the setpoint value, a significant improvement over the prior art data shown in FIG. 5, 511, and FIG. 4. The capability demonstrated by embodiments of the Instant Invention to measure and control key precursor mass flow rates with this accuracy enables accurate, consistent delivery of targeted key precursor mass flow rates and key ratios between key precursor additives which enable high quality CNT manufacturing with cost structures competitive for commercial adoption. Manufacturing of CNTs with Present Invention FCCVD method

[0127] The following non-limiting examples further describe the practice of the instant invention.

[0128] The CNT manufacturing of the Instant Invention was carried out in a horizontallyAttorney Docket No.: 072174-06101 oriented downflow tubular reactor using the present invention embodiment FIG 3 FCCVD system, The reactor was heated to a wall set point temperature of 1200 °C, and system pressure was maintained in a range from 103 to 107 kPa. Ferrocene and thiophene (Sigma Aldrich, purity ≥99%) were used as iron (Fe) and sulfur nanoparticle catalyst precursors, respectively, in key process ratios. Ferrocene was sublimed in the cartridge 315 described above, and thiophene was vaporized in a liquid bubbler (MTI Corporation, 150 mL). The setpoint Fe catalyst flow rate was set to provide for the CNT synthesis procedure enabling S:Fe ratios between 0.09 to 0.9. The thiophene bubbler was chilled below -6 °C to lower its vapor pressure for better control over the molar flow rate and enabling S:Fe ratios between 0.09 to 0.9. The acoustic sensor was installed downstream of the ferrocene cartridge but upstream of the thiophene-carried gas mixing point. N2(Airgas, UHP grade) carried all precursor catalyst vapors. Catalyst vapors were initially diverted into a purging flask for about 15 minutes to achieve steady state. For the CNT growth experiments, the catalyst carrying stream was mixed with additional N2inert, H2(Airgas, UHP grade), and CH4(Airgas, UHP grade) before injecting into the tubular reactor through a 3 to 4 mm ID injection tube.

[0129] The CNT manufacturing experiments reported herein were conducted for 30-60 minutes. After each experiment, the synthesized material was collected and analyzed using thermogravimetric analysis (TGA) (Mettler Toledo, TGA / DSC3+) to determine characteristics of the CNT manufactured material. This FCCVD setup and explored S / Fe ratios were utilized to build Process Maps based on S / Fe ratios related to key properties of the CNT manufacturing process material as discussed in the following present invention examples. Present Invention Example 3 CNT Manufacturing using Acoustic Sensor and Key S / Fe ratio embodiments

[0130] CNT manufacturing process maps were constructed using data produced from manufacturing batches of CNT using a FCCVD system and technology of the Instant Invention.Attorney Docket No.: 072174-06101 FIG.6 presents a process map of S / Fe key process ratios using different precursor mass flow rates to achieve the key process ratio with CH4to solid carbon conversion measured in weight % (wt%). (Input S / Fe key process ratio to solid carbon conversion rate generally can be an important process metric for CNT manufacturing quality and performance). Of the solid carbon produced, the selectivity to CNT materials versus other undesired carbon materials averaged approximately, 93-95% when carbon conversion rates were high. In this process map, values as high as 17% are achieved, which is a significant improvement over the prior art (Weller 2019 reports carbon conversion levels of less than 1% and Lee I 2021 reports carbon conversion levels of 1% - 5%).

[0131] Additionally, it is very clear in this process map that there are contours produced by the data which indicate that even small variabilities from the ferrocene and / or thiophene mass flow rate setpoints can move the CNT manufacturing process into poor productivity regions. Additionally, in such poor productivity regions of the process map, high levels of undesired carbon solid is formed, reducing the CNT yield and degrading the CNT quality. As illustrated in FIGS. 2, 4-5, prior art technology can easily approach 60% variability in the measured precursor mass flow rate and potentially higher depending on operator, setup procedure and other variables. With such high variability, it would be expected that the prior art CNT manufacturing process would have lower, undesired performance not enabling cost structures suitable for commercial adoption. Use of the acoustic sensor to control the key process ratio S / Fe within a targeted and desired range demonstrates the significant robustness and operability conferred by using the instant invention.

[0132] FIG.7 presents a process map of S / Fe key process ratios using different precursor mass flow rates to achieve the key process ratio with carbon solid production rates. (Again, input S / Fe key process ratio to solid carbon conversion rate generally can be an important process metric for CNT manufacturing quality and performance). Of the solid carbon produced, theAttorney Docket No.: 072174-06101 selectivity to CNT materials versus other undesired carbon materials averaged approximately, 93-95% when production rates were high. For purposes of high quality CNT manufacturing commercially viable cost structures, it is preferred to achieve higher solid carbon production rates and high selectivity to CNT of the solid carbon produced.

[0133] Additionally, it is clear in FIG.7 that the process map has contours that rapidly change to productivities of CNT production that are not desired such as 18 mg / hr and 80 mg / hr. These undesired CNT production rates are avoided using the present invention using the acoustic sensor to measure ferrocene mass flow rates and coupled with a control scheme to maintain the mass flow rates and thereby the key process ratio, S / Fe. It is understood by one skilled in the art that the CNT manufacturing condition which provides for 564 mg / hr of CNT production can easily be reduced almost an order of magnitude by a 50% or more change (when variability errors are stacked) in ferrocene and / or thiophene mass flow rates as is typical of the errors in prior art as illustrated in FIGS.2A-2D, 4, and 5.

[0134] FIG.8 presents a process map of S / Fe ratios (ferrocene and thiophene mass flow rate ratios) with CNT average aspect ratios. In general, higher aspect ratios are preferred for most commercial applications and is an indicator of the CNT quality with higher aspect ratios an indicator for higher quality. The prior art reports typically have aspect ratios of 1000-2000 for most CNT FCCVD systems. FIGS. 6-8 along with other relevant, measured data of the CNTs produced and the process performance must be considered in conjunction when identifying preferred embodiments of the instant invention such that optimizing CNT production rate, CNT aspect ratio, and other quality factors must be done to achieve the highest quality CNT and CNT manufacturing process performance. It is clear that setting the proper key process ratio and maintaining that process ratio are important for the high quality, competitive cost CNT manufacturing process design. Generally, the CNTs manufactured with targeted S / Fe ratios with high CNT productionAttorney Docket No.: 072174-06101 rates and higher carbon conversion rates also had raman spectroscopy G / D ratios higher than 20, which is used in the prior art as an indicator of higher quality CNTs. Uses and Applications

[0135] It has been shown that key process precursors mass flow rates can be highly sensitive to temperature variabilities, particularly at temperatures below 343 K. It has been successfully shown that acoustic sensors are effective for monitoring and quantifying the ferrocene vapor mass flow rate, achieving an accuracy within ±10% when benchmarked against UV-Vis spectrophotometer concentration measurements. This instant invention eliminates the dependency on the assumptions of vapor-solid equilibrium common in the prior art and establish a novel method for controlling and quantifying key precursor mass flow rates including the key process ratios necessary for high quality CNT manufacturing.

[0136] The implementation of a feedback control system to maintain a consistent ferrocene vapor flow rate in both inter-and intra-manufacturing runs has also been shown.

[0137] The improved method can further include utilizing a controlled environmental condition for the FCCVD reactor, and / or changing the catalyst injecting methods to address the FCCVD synthesis process to optimize and improve the stability of the CNT production rate.

[0138] The use of acoustic sensors in FCCVD reactors to make CNTs (such as FWCNTs) and other products provide significant advantages over the prior art methods and systems, herein where the focus is the quantitative control of the input molar S:Fe ratio by controlling the respective mass flowrates of sulfur and iron or similar process additives, as has found that to be highly critical for effective, high quality CNT manufacturing. See FIGS.6-8.

[0139] These prior art methods and systems do not have any quantitative control methodologies and no PID control methodologies for controlling the S:Fe ratio and thereby the CNT manufacturing process is not controlled, often showing high variability in the productAttorney Docket No.: 072174-06101 characteristics and quality. The present invention methods and systems enable the accurate control of these molecules mass flow rates and thereby providing a method to control their ratio to achieve high quality CNT formation as well as higher productivities. Such quantitative control methods can enable CNT production with high uniformity in diameter, length, and / or chirality with suitable catalyst nanoparticles and key process ratios.

[0140] An acoustic sensor is placed inline with the process chemicals of interest (such as sulfur source and iron source), and measures the concentration (mass flow rates) of such chemicals, respectively and independently, when in a binary gas / vapor stream. The sulfur and iron start in some molecular format (thiophene and ferrocene in this case). As the sulfur and iron containing molecules enter the reactor chamber, they will be decomposed through thermal energy means liberating the sulfur and iron atoms. The input concentrations of S and Fe have importance for the production of Fe nanoparticles (FeNPs). Process setpoints for the specific chemicals can be placed in a controlled logic format and / or via manual adjustment of setpoints and the data provided by the sensor will control the chemical compositions in the streams to the desired setpoint. Using process knowledge and experimental investigations, the appropriate ratio of S:Fe is determined and highly important that it is controlled to the setpoint.

[0141] The use of acoustic sensors in FCCVD reactor to make CNTs (such as FWCNTs) and other products, where the focus is the specific control of preformed Fe nanoparticles (FeNPs) mass flowrate produced ex-situ or outside of the reactor. This is differentiated from the measurement and control of only molecular species that contain iron. Here, the iron is in zero valiant state existing as a metal with nanometer size dimensions, typically less than 10 nm, preferably less than 5 nm. There are various routes for how the FeNPs can be produced ex- situ, for example, using a plasma torch where a metallic iron source and a sulfur source or similar key process additive (controlled by an acoustic sensor) can be combined going into the plasma torch resulting in FeNPs. These FeNPs will then be flowed through the acoustic sensorAttorney Docket No.: 072174-06101 enabling mass flow rate measurement of the FeNPs so that the mass flow rate can be controlled using control logic.

[0142] In high quality CNT manufacturing, controlling C:Fe ratios can have importance. With fine control for FeNPs size, size distribution and number density, using the control of Fe input concentration (mass flow rate controlled by acoustic sensors), and an accurate carbon source input concentration (mass flow rate), controlled ratios of C to Fe will improve control of CNT diameter more accurately, CNT aspect ratio and ultimately CNT chirality control. The FeNPs can be produced either in the reactor chamber using a combination of sulfur and iron containing molecules that decompose in a controlled fashion and / or preformed ex-situ to the reactor chamber in another device, such as a plasma torch.

[0143] While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described and the examples provided herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. The scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.

[0144] The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated herein by reference in their entirety, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein.

[0145] Amounts and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example,Attorney Docket No.: 072174-06101 a numerical range of approximately 1 to approximately 4.5 should be interpreted to include not only the explicitly recited limits of 1 to approximately 4.5, but also to include individual numerals such as 2, 3, 4, and sub-ranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges reciting only one numerical value, such as “less than approximately 4.5,” which should be interpreted to include all of the above-recited values and ranges. Further, such an interpretation should apply regardless of the breadth of the range or the characteristic being described.

[0146] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently disclosed subject matter belongs. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the presently disclosed subject matter, representative methods, devices, and materials are now described.

[0147] Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims.

[0148] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.

[0149] As used herein, the term “about” and “substantially” when referring to a value or to an amount of mass, weight, time, volume, concentration or percentage is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosedAttorney Docket No.: 072174-06101 method.

[0150] As used herein, the term “substantially perpendicular” and “substantially parallel” is meant to encompass variations of in some embodiments within ±10° of the perpendicular and parallel directions, respectively, in some embodiments within ±5° of the perpendicular and parallel directions, respectively, in some embodiments within ±1° of the perpendicular and parallel directions, respectively, and in some embodiments within ±0.5° of the perpendicular and parallel directions, respectively.

[0151] As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D. REFERENCES

[0152] PCT Patent Appl. Publ. No. WO / 2005 / 085130, filed March 9, 2005, entitled “Single, multi-walled, functionalized and doped carbon nanotubes and composites thereof,” to Esko Kauppinen, et al. (“Kauppinen ’130 PCT Application”).

[0153] U.S. Patent Appl. Publ. No. 2020 / 0239316, filed April 10, 2010, entitled “Method and apparatus for producing carbon nanostructures,” to Mikhail Rudolfovich Predtechenskiy (“Predtechenskiy ’316 Application”).

[0154] Japan Patent No. 60-32818, entitled “Gas phase method of manufacturing Carbon Fibers,” issued February 22, 1985, to Ysuto Komatsu, et al. (“Komatsu ’818 Japan Patent”).

[0155] Bogdanova, A. R., et al., “The role of sulfur in the CVD carbon nanotube synthesis,” Carbon, 2023, 210, 118051 (“Boddanova 2023”).

[0156] Bronikowski, M. J., et al.,”Gas-phase production of carbon single-walled nanotubes from carbon monoxide via the HiPco process: A parametric study,” J. of Vac. Sci. & Tech. A, 2001, 19, 1800–1805 (“Bronikowski 2001”).Attorney Docket No.: 072174-06101

[0157] Cheng, H. M., et al., “Large-scale and low-cost synthesis of single-walled carbon nanotubes by the catalytic pyrolysis of hydrocarbons,” Appl. Phys. Lett., 1998, 72, 3282–3284 (“Cheng 1998”).

[0158] Constantinoiu, I., et al., “ZnO Metal Oxide Semiconductor in Surface Acoustic Wave Sensors: A Review,” Sensors, 2200, 20, 5118 (“Constantinoiu 2020”).

[0159] Ding, F., et al., “Dislocation theory of chirality-controlled nanotube growth,” Proc. Natl. Acad. Sci., 2009, 106, 2506–2509 (“Ding 2009”).

[0160] Endo, M., “Grow carbon fibers in the vapor phase,” Chemtech, 1988, 18(9), 568-576 (“Endo 1988”).

[0161] Fulem, M., et al., “Recommended vapor pressure and thermophysical data for ferrocene,” J. Chem. Thermodyn., 2013, 57, 530–540 (“Fulem 2013”).

[0162] Gökstorp, F. K. A., et al., “Flow Simulations Including Iron Nanoparticle Nucleation, Growth and Evaporation for Floating Catalyst CNT Production,” Catalysts, 2020, 10, 1383 (“Gökstorp 2020”).

[0163] Grimm, S., et al., “Mechanism and Kinetics of the Thermal Decomposition ofFe(C5H5)2in Inert and Reductive Atmosphere: A Synchrotron‐AssistedInvestigation in AMicroreactor,” Adv. Mater. Interfaces, 2022, 9, 2200192 (“Grimm 2022”).

[0164] Hoecker, C., et al., “The influence of carbon source and catalyst nanoparticles on CVD synthesis of CNT aerogel,” Chem. Eng. J., 2017, 314, 388–395 (“Hoeker 2017”).

[0165] Hoecker, C., et al., “Catalyst nanoparticle growth dynamics and their influence on product morphology in a CVD process for continuous carbon nanotube synthesis,” Carbon, 2016, 96, 116–124 (“Hoecker 2016”).

[0166] Hou, G., et al., “The effect of a convection vortex on sock formation in the floating catalyst method for carbon nanotube synthesis,” Carbon, 2016, 102, 513–519 (“Hou 2016”).

[0167] Hussain, A., et al., “Floating catalyst CVD synthesis of single walled carbon nanotubesAttorney Docket No.: 072174-06101 from ethylene for high performance transparent electrodes,” Nanoscale, 2018, 10, 9752–9759 (“Hussain 2018”).

[0168] Kaskela, A., et al., “Highly individual SWCNTs for high performance thin film electronics,” Carbon, 2016, 103, 228–234 (“Kaskela 2016”).

[0169] Khavarian, M., et al., “Effects of Growth Parameters on the Morphology of Aligned Carbon Nanotubes Synthesized by Floating Catalyst and the Growth Model,” Fuller. Nanotub. Carbon Nanostructures, 2013, 21, 765–777 (“Khavarian 2013”).

[0170] Kirillov, V. A., et al., “Critical Phenomena in Trickle-Bed Reactors,” Ind. Eng. Chem. Res., 2005, 44, 9727–9738 (“Kirillov 2005”).

[0171] Lee, S.-H., et al., “Deep-injection floating-catalyst chemical vapor deposition to continuously synthesize carbon nanotubes with high aspect ratio and high crystallinity,” Carbon, 2021, 173, 901–909 (“Lee I 2021”).

[0172] Lee, S.-H., et al., “Strong and Highly Conductive Carbon Nanotube Fibers as Conducting Wires for Wearable Electronics,” ACS Appl. Nano Mater., 2021, 4, 3833–3842 (“Lee II 2021”)

[0173] Lee, S.-H., et al., “Synthesis of carbon nanotube fibers from carbon precursors with low decomposition temperatures using a direct spinning process,” Carbon, 2017, 124, 219– 227 (“Lee 2017”).

[0174] Martin, S. J., et al., “Gas sensing with acoustic devices,” in 1996 IEEE Ultrasonics Symposiumi Proceedings vol. 1 423–434 (IEEE, San Antonio, TX, USA), 1996 (“Martin 1996”).

[0175] Masuda T., et al., “The production of long vapor grown carbon fibers at high rates,” Carbon, 1992, 30(1), 124-126 (“Masuda 1992”).

[0176] Mirbagheri, S. A., et al., “Macroscopic Synthesis of Vertically Aligned Carbon Nanotubes Using Floating Catalyst Chemical Vapor Deposition Method,” Jpn. J. Appl. Phys.,Attorney Docket No.: 072174-06101 2011, 51, 015101 (“Mirbagheri 2011”).

[0177] Moisala, A., et al., “Single-walled carbon nanotube synthesis using ferrocene and iron pentacarbonyl in a laminar flow reactor,” Chem. Eng. Sci., 2006, 61, 4393–4402 (“Moisala 2006”).

[0178] Motamedi, M. E., “Acoustic sensor technology,” in 1994 IEEE MTT-S International Microwave Symposium Digest (Cat. No.94CH3389-4) 521–524 (IEEE, San Diego, CA, USA), 1994, doi:10.1109 / MWSYM.1994.335449 (“Motamedi 1994”).

[0179] Nikolaev, P., et al., “Gas-phase catalytic growth of single-walled carbon nanotubes from carbon monoxide,” Chemical Physics Letters, 1999, 313(1)-(2), 91-97 (“Nikolaev 1999”).

[0180] Nguyen, D., et al., “Reaction-driven instabilities in down-flow packed beds. Proc. R. Soc. Lond. Ser. Math. Phys. Sci., 1997, 450, 1–21 (“Nguyen 1997”).

[0181] Oikonomou, A., et al., “Growth, dispersion, and electronic devices of nitrogen-doped single-wall carbon nanotubes,” Phys. Status Solidi B, 2012, 249, 2416–2419 (“Oikonomou 2012”).

[0182] Park, J. H., et al., “Continuous synthesis of high-crystalline carbon nanotubes by controlling the configuration of the injection part in the floating catalyst chemical vapor deposition process,” Carbon Lett., 2020, 30, 613–619 (“Park 2020”).

[0183] Qiao, R., et al., “Continuous gas-phase synthesis of iron nanoparticles at ambient conditions with controllable size and polydispersity,” J. Colloid Interface Sci., 2024, 658, 986– 996 (“Qiao 2024”).

[0184] Schildhauer, T. J., et al., “Heat transport in structured packings with two-phase co- current downflow,” Chem. Eng. J., 2012, 185–186, 250–266 (“Schildhauer 2012”).

[0185] Sen, R., et al., “Carbon Nanotubes by the metallocene route,” Chemical Physics Letters, 1997, 267, 276-280 (“Sen 1997”).

[0186] Shibuki, S., et al., “Effect of catalyst-supporting layer on emissivity of carbonAttorney Docket No.: 072174-06101 nanotubes grown by floating catalyst chemical vapor deposition,” Meas. Sens., 2021, 18, 100227 (“Shibuki 2021”).

[0187] Stanford Research Systems, BGA244 sensor manual - 2022 Sept Stanford Research Systems, 2016 (“Stanford Research 2016”).

[0188] Sun, D., et al., “Flexible high-performance carbon nanotube integrated circuits,” Nat. Nanotechnol.6, 156–161 (“Sun 2011”).

[0189] Tessonnier, J.-P., et al., “Recent Progress on the Growth Mechanism of Carbon Nanotubes: A Review,” ChemSusChem, 2011, 4, 824–847 (“Tessonnier 2011”).

[0190] Tibbetts G G., “Vapor-grown carbon fibers: status and prospects,” Carbon, 1989, 27(5), 745-747 (“Tibbetts 1989”).

[0191] Vazquez-Pufleau, M., et al., “Mapping carbon nanotube aspect ratio, concentration and spinning in FCCVD synthesis controlled by sulphur,” Carbon Trends, 2024, 100355 doi:10.1016 / j.cartre.2024.100355 (“Vazquez-Pufleau 2024”).

[0192] Weller, L. et al., “Mapping the parameter space for direct-spun carbon nanotube aerogels,” Carbon, 2019, 146, 789-812 (“Weller 2019”).

[0193] Xie, S., et al., “Controllable preparation and properties of single- / double-walled carbon nanotubes,” Sci. Technol. Adv. Mater., 2005, 6, 725–735 (“Xie 2005”).

[0194] Yadav, M. D., et al., “Kinetic study of single-walled carbon nanotube synthesis by thermocatalytic decomposition of methane using floating catalyst chemical vapour deposition,” Chem. Eng. Sci., 2019, 196, 91–103 (“Yadav 2019”).

[0195] Yu, B., et al., “Bulk Synthesis of Large Diameter Semiconducting Single-Walled Carbon Nanotubes by Oxygen-Assisted Floating Catalyst Chemical Vapor Deposition,” J. Am. Chem. Soc., 2011, 133, 5232–5235 (“Yu 2011”).

[0196] Zhang, Q., et al., “Modulating the diameter of carbon nanotubes in array form via floating catalyst chemical vapor deposition,” Appl. Phys. A, 2009, 94, 853–860 (“ZhangAttorney Docket No.: 072174-06101 2009”).

[0197] Zhang, R., et al., “Nucleation and Growth of Nanoparticles in the Atmosphere,” Chem. Rev., 2012, 112, 1957–2011 (“Zhang 2012”).

Claims

Attorney Docket No.: 072174-06101 WHAT IS CLAIMED IS:

1. A system, comprising: (a) a reactor chamber configured to facilitate the production of nanoparticles; (b) a delivery system configured to supply nanoparticle reaction additives to the reactor chamber; (c) an acoustic sensor disposed between the delivery system and the reactor chamber, wherein the acoustic sensor is configured to: (i) measure real-time stream compositions of the reaction additives; (ii) determine mass flow rates of the reaction additives; and (d) a control unit communicatively coupled to the acoustic sensor and the delivery system, wherein the control unit is configured to: (i) receive measurements from the acoustic sensor; (ii) adjust the mass flow rates of the reaction additives based on the received measurements to conform to process recipe setpoints; (iii) control the mass ratios of the reaction additives to enable the production of the nanoparticles.

2. The system of Claim 1, wherein the nanoparticles are nanotubes.

3. The system of Claim 1, wherein the nanoparticles are carbon nanotubes (CNTs).

4. The system of Claim 1, wherein the nanoparticles are few-walled carbon nanotubes (FWCNTs).

5. The system of Claims 1, wherein the nanoparticles are Fe nanoparticles.Attorney Docket No.: 072174-06101 6. The system of any of Claims 1-5, wherein (a) the system is a floating catalysts chemical vapor deposition (FCCVD) manufacturing system, and (b) the reactor chamber is a FCCVD reactor chamber.

7. The system of any of Claims 1-6, wherein the system comprises a bank of process gases.

8. The system of Claim 7, wherein the bank of process gases comprises one or more process gases selected from the group consisting of inert gases and carbon atom source gases.

9. The system of any of Claim 1-8, wherein (a) the delivery system is configured to supply a metallic nanoparticle reaction additive to the reactor chamber; (b) the system comprises a metal delivery source for supplying the metallic nanoparticle reaction additive, and (c) the metallic nanoparticle reactive additive comprises a metal atom.

10. The system of Claim 9, wherein the metal atom is Fe.

11. The system of Claim 10, wherein the metallic nanoparticle reaction additive is ferrocene.

12. The system of Claim 9, wherein the metallic nanoparticle reaction additive is a metallic nanoparticle reaction additive used for carbon nanotube manufacturing.Attorney Docket No.: 072174-06101 13. The system of any of Claims 9-12, wherein the metal delivery source comprises a sublimater.

14. The system of any of Claim 1-13, wherein (a) the delivery system is configured to supply a sulfur nanoparticle reaction additive source to the reactor chamber; (b) the system comprises a sulfur delivery source for supplying the sulfur nanoparticle reaction additive source, and (c) the sulfur nanoparticle reactive additive source comprises sulfur.

15. The system of Claim 14, wherein the sulfur nanoparticle reaction additive source is thiophene.

16. The system of any of Claims 14-15, wherein the sulfur delivery source comprises a source bubbler.

17. The system of any of Claims 1-16, wherein the acoustic sensor is an acoustic gas sensor.

18. The system of Claim 17, wherein the acoustic sensor is a binary acoustic gas sensor.

19. The system of any of Claims 1-18, wherein (a) the delivery system is configured to supply a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive comprises a metal atom (M);Attorney Docket No.: 072174-06101 (b) the delivery system is configured to supply a sulfur nanoparticle reaction additive to the reactor chamber; and (c) the acoustic sensor is operable to measure the ratio of S:M to control the quality of the nanoparticles manufactured by the system.

20. The system of any of Claims 1-19, wherein (a) the delivery system is configured to supply a sulfur nanoparticle reaction additive to the reactor chamber; (b) the bank of process gases comprises at least one carbon-containing gas; and (c) the acoustic sensor is operable to measure the ratio of C:S to control the quality of the nanoparticles manufactured by the system.

21. The system of any of Claims 1-20, wherein (a) the delivery system is configured to supply a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive comprises a metal atom (M); (b) the bank of process gases comprises at least one carbon-containing gas; and (c) the acoustic sensor is operable to measure the ratio of C:M to control the quality of the nanoparticles manufactured by the system.

22. The system of any of Claims 1-21, wherein (a) the delivery system is configured to supply a metallic nanoparticle reaction additive to the reactor chamber, wherein the metallic nanoparticle reactive additive comprises a metal atom (M); (b) the delivery system is configured to supply a sulfur nanoparticle reactionAttorney Docket No.: 072174-06101 additive to the reactor chamber; (c) the bank of process gases comprises at least one carbon-containing gas; and (d) the acoustic sensor is operable to measure at least two of (i) the ratio of S:M, (ii) the ratio of C:S, and (iii) the ratio of C:M, to control the quality of the nanoparticles manufactured by the system.

23. The system of any of Claims 19-22, wherein the ratio of S:M is set at a predetermined S:M ratio and the system is operable to maintain the ratio of the S:M at the S:M predetermined ratio ± 10%.

24. The system of any of Claims 19-24, wherein the ratio of C:M is set at a predetermined C:M ratio and the system is operable to maintain the ratio of the C:M at the C:M predetermined ratio ± 10%.

25. The system of any of Claims 19-24, wherein the ratio of C:S is set at a predetermined C:S ratio and the system is operable to maintain the ratio of the C:S at the C:S predetermined ratio ± 10%.

26. A method for manufacturing nanoparticles using a system with real-time control of reaction additives, the method comprising: (a) providing a reactor chamber suitable for the production of nanoparticles; (b) delivering nanoparticle reaction additives to the reactor chamber using a delivery system; (c) measuring real-time stream compositions and mass flow rates of the nanoparticle reaction additives using an acoustic sensor disposed between theAttorney Docket No.: 072174-06101 delivery system and the reactor chamber; (d) communicating the measurements from the acoustic sensor to a control unit; (e) adjusting, by the control unit, the mass flow rates of the nanoparticle reaction additives based on the measurements; and (f) controlling, by the control unit, the mass ratios of the nanoparticle reaction additives based on the adjustments to enable the production of the nanoparticles.

27. The method of Claim 27, wherein the method is performed using a system selected from the group consisting of the systems of Clams 1-25.

Images