Patent Application
20180148337
Single-wall nanotube containing compositions for use in energetic applications, and methods of their manufacture are described.
Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. These sheets are rolled at specific and discrete (“chiral”) angles, and the combination of the rolling angle and radius decides the nanotube properties; for example, whether the individual nanotube shell is a metal or semiconductor. Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). Individual nanotubes naturally align themselves into “ropes” held together by van der Waals forces, more specifically, pi-stacking These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. Owing to their extraordinary thermal conductivity, mechanical, and electrical properties, carbon nanotubes find applications as additives to various structural materials.
The application is directed to single-wall nanotube containing compositions for use in energetic applications, and methods of their manufacture.
Many embodiments are directed to combustion catalysts containing a mixture of high-purity single-walled carbon nanotubes and non-oxidizable metallic nanoparticles.
In some embodiments, no more than 5% of the carbon is non-single-walled carbon nanotubes.
In other embodiments the metallic nanoparticles are from 2 to 5 nm in dimension.
In still other embodiments the metallic nanoparticles are carbon encapsulated iron. In some such embodiments the metallic nanoparticles are encapsulated in a carbon fullerene material.
In yet other embodiments the metallic nanoparticle comprise no greater than 20% of the mass of the mixture.
In still yet other embodiments the single-walled carbon nanotubes comprise at least 95% of the mass of carbon, wherein the metallic nanoparticles are carbon encapsulated iron comprising no greater than 20% of the mass of the mixture.
Many other embodiments are directed to rocket motor opacifiers containing a mixture of high-purity single-walled carbon nanotubes and non-oxidizable metallic nanoparticles.
In some embodiments, no more than 5% of the carbon is non-single-walled carbon nanotubes.
In other embodiments the metallic nanoparticles are from 2 to 5 nm in dimension.
In still other embodiments the metallic nanoparticles are carbon encapsulated iron. In some such embodiments the metallic nanoparticles are encapsulated in a carbon fullerene material.
In yet other embodiments the metallic nanoparticle comprise no greater than 20% of the mass of the mixture.
In still yet other embodiments the single-walled carbon nanotubes comprise at least 95% of the mass of carbon, wherein the metallic nanoparticles are carbon encapsulated iron comprising no greater than 20% of the mass of the mixture.
Still many other embodiments are directed to methods of synthesizing a combustion catalyst including:
In some embodiments the source of carbon is selected from the group of benzene, acetylene, CO, and a mixture of CO and hydrogen.
In other embodiments the organometallic catalyst is an iron-containing molecule. In some such embodiments the iorn-containing molecule is ferrocene.
In still other embodiments the pressure in the reactor during reaction is from 30-100 atm, and the temperature is at least 1050° C.
In yet other embodiments the single-walled carbon nanotubes comprise at least 95% of the mass of carbon in the mixture, and wherein the metallic nanoparticles are carbon encapsulated iron comprising no greater than 20% of the mass of the mixture.
Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.
The description will be more fully understood with reference to the following figures, which are presented as exemplary embodiments of the invention and should not be construed as a complete recitation of the scope of the invention, wherein:
Turning now to the drawings, single-walled nanotubes for use as additives in energetic materials, and methods for synthesizing such materials are described. In many embodiments, the single-walled carbon nanotube (SWNT) additives comprise a mixture of high-purity SWNT and carbon encapsulated iron nanoparticles. In various such embodiments the SWNT mixtures comprises no more than 5% non-SWNT carbon. In some such embodiments, the iron nanoparticles are from 2-5 nm. In many embodiments, the method of synthesizing the SWNTs comprises a high-pressure carbon monoxide (HiPCO) process. Various embodiments are also directed to the use of SWNT mixtures for use as additives in energetic processes, such as, for example, rocket motors.
The addition of nano-sized components to energetic materials has been investigated for nearly two decades, with studies showing a direct correlation between decreased particle size and increased burn rate. Explaining this effect is straightforward—smaller particles will, for a given mass of material, have a higher surface area and therefore more reactive sites. While this effect can be substantial, stabilizing the nanoparticles against unwanted oxidation is often a challenge. (See, e.g., Armstrong, R. W., et. al., Nano Lett. 2003, Vol. 3, No. 2, 253-255; Dreizin, E. L., Progress in Energy and Combustion Science 35 (2009) 141-167; Meda, L., et. al., Compos. Sci. Tech. 65 (2005) 769-773; Meda, L., et. al., Mater. Sci. Eng. C 27 (2007) 1393-1396; Pivkina, A., et. al., Propellants, Explosives, Pyrotechnics 29 (2004), No. 1, 39-48; Brousseau, P., Anderson, C. J., Propellants, Explosives, Pyrotechnics 27, 300-306 (2002); Isert, S., Groven, L. J., Lucht, R. P., and Son, S. F.; Combustion and Flame 162 (2015) 1821-1828; Dlott, D. D., Materials Science and Technology, 2006, vol 22 issue 4, 463-473; Rossi, C., Propellants Explos. Pyrotech. 2014, 39, 323-327, the disclosures of which are incorporated herein by reference.)
According to embodiments, SWNTs synthesized according to specific methods may be used as effective additives to energetic materials. In such embodiments, marked improvement in impulse, acceleration and burn rate is seen even at extremely low SWNT loadings by mass. More specifically, it has been discovered that high-purity SWNT carbon containing carbon coated metallic nanoparticles may be used to catalyze combustion, such as, for example, in a rocket motor. Although not to be bound by theory, it is believed that the increased thermal conductivity of SWNTs allows the motor to heat up and burn at a more rapid pace. (See, e.g., Hone, J., et. al., Appl. Phys. A 74, 339-343 (2002); and Sun, K. Stroscio, M. A., Dutta, M., J. Appl. Phys. 105, 074316 (2009), the disclosures of which are incorporated herein by reference.) Additionally, slightly oxidized carbon nanomaterials have been shown to catalyze the combustion of nitrogenated carbon, a common monopropellant. (See, e.g., Chaban, V. V, Fileti, E. E., Prezhdo, O. V., J. Phys. Chem. Lett. 2015, 6, 913-917; Sabourin, J. L., et. al. ACS Nano, 2009, vol 3 issue 12, 3945-3954; and Zhang, C.; Wen, Y.; Xue, X., ACS Appl. Mater. Interfaces 2014, 6, 12235-12244, the disclosures of which are incorporated herein by reference.)
As shown in
The HiPCO synthesis, in accordance with embodiments, produces high-purity SWNT materials with very low amounts of non-SWNT carbon in the end product (typically less than 5%). The product also includes metallic nanoparticles (e.g., 2-5 nm). In many embodiments these nanoparticles are encased in carbon such that 20% of the mass of the nanoparticle is metal (e.g., iron). These iron nanoparticles are the seeds from which the SWNTs grow and are protected from further oxidation or reaction by the encapsulating carbon, which may be present in the form of carbon buckball, which forms during the synthesis process. Accordingly, in many embodiments the synthesis according to embodiments produces a mixture of SWNT's in high purity (e.g., ˜95% or higher) interspersed with carbon encases nanoparticles (e.g., Fe nanoparticles).
Many embodiments are directed to combustion catalysis additives comprising mixtures of SWNT carbon and metal nanoparticles. In many embodiments, the additives comprise a mixture of high-purity SWNT carbon (e.g., at least 95% pure) and metallic carbon encapsulated nanoparticles (e.g., iron nanoparticles having a size of 2-5 nm). In many such embodiments up to 20% of the mixture by mass can be iron. In some such embodiments the nanoparticles are encapsulated in a carbon material, such as, for example, spherical carbon (e.g., buckyballs) to prevent further reaction or oxidation of the metallic nanoparticle prior to use.
Accordingly in many embodiments the combustion catalyst material may comprise the following mixture:
In some such embodiments, the SWNT-catalyzed additives may be added to a rocket motor to improve combustion. In such embodiments, it will be understood that any energetic material may be used, however, the opacifier (carbon black) is replaced by the combustion catalysis materials described herein.
Results of experiments conducted on rocket motors incorporating combustion catalysis SWNT materials in accordance with embodiments are provided in
As shown in
In summary, it has been surprisingly discovered that SWNT/metal nanoparticle compositions in accordance with embodiments may be used to improve combustion in energetic material applications. Although not to be bound by theory, the combination of small iron nanoparticles, high thermal conductivity and carbon nanomaterial-catalyzed combustion are observed to increase burn rates and total impulse seen in the tests performed. While the latter two components may be found in other carbon nanomaterials, only those produced in accordance with embodiments will contain the carbon encased iron nanoparticles, which are surprisingly found to improve combustion and are also stabilized against oxidation or other reactions.
Although specific combustion catalysis materials, their application and methods of their manufacture, have been provided, it should be understood that other materials and methods may also incorporate the improved combustion catalysis characteristics according to embodiments.
As can be inferred from the above discussion, the above-mentioned concepts can be implemented in a variety of different implementations in accordance with embodiments of the invention. Accordingly, although the present invention has been described in certain specific aspects, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that the present invention may be practiced otherwise than specifically described. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive.
The current application claims priority to U.S. Provisional Patent Application No. 62/428,388, filed, Nov. 30, 2016, the disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62428388 | Nov 2016 | US |
