Patent Application
20250162959
This present invention is directed to a powder comprising a composite of primary nanoparticles of aluminum and/or aluminum oxide, each nanoparticle being separated from the others by an intervening organic or polymeric material, and formed into secondary particles that are substantially larger than the primary nanoparticles. The design of this powder improves combustion performance and facilitates desirable mixing and processing characteristics when introduced into material formulations such as a solid rocket fuels, propellants, and explosives.
A solid rocket motor or composite propellant rocket motor is a propulsion system with a motor that uses solid propellants comprising a fuel, an oxidizer, and a polymer binder material. The solid propellant is normally in the form of a propellant grain located within the interior of the rocket motor pressure vessel, or combustion chamber, and burned to produce hot gases which, in turn, exit through the throat and expansion nozzle of the rocket motor at high velocity to provide thrust which propels the rocket in the opposite direction.
Powdered aluminum metal is commonly used in solid propellant formulations to increase energy density and specific impulse. Certain explosives formulations contain aluminum powder, which burns during the explosion and contributes to secondary blast effects. Ultrafine or nanoparticulate aluminum has the potential to increase combustion rates due to its much higher surface-to-volume ratio. However, these aluminum materials suffer from difficulties of manufacture, safety hazards, and increasing amount of aluminum oxide content as the particle size decreases. Due to the strongly exothermic aluminum (Al) to aluminum oxide (Al2O3) reaction, powdered aluminum has long found use in energetic materials including solid propellants. The rate of reaction is proportional to the surface area available for oxidation, and thus there is significant interest in the use of nanoscale Al powders in energetic materials. Commercial ultrafine Al powders are typically produced by electro-explosion of aluminum wire, or by plasma synthesis methods. However, the commercially available powders are of 100-200-nm particle diameter, well above the nano regime at which dramatic increases in surface area and reactivity are expected. In fact, some studies on truly nanoscale Al powders found that they perform more poorly than expected because a native aluminum oxide layer forms on the surface of metallic Al upon exposure to air. In the case of nanoscale Al powders, the aluminum oxide layer encompasses a large fraction of the overall particle mass, leaving little remaining reactive aluminum in Al nanopowders formed by conventional methods.
Each of the prior art methods for producing aluminum nanoparticle powders results in powders comprised of agglomerated nanoparticles. See C. E. Johnson, S. Fallis, A. P. Chafin, T. J. Groshens, K. T. Higa, I. M. K. Ismail, T. W. Hawkins, Journal of Propulsion and Power 2007, 23, 669-682. Aluminum nanopowders have previously been commercially produced by three methods: electrical explosion of metallic wire, (B. Baschung, D. Grune, H. H. Licht, M. Samirant, in K. K. Kuo, L. T. DeLuca (editors), Combustion of Energetic Materials, New York, NY: Begell House 2002, 219-25.), plasma condensation, and mechanical milling (L. Meda, G. Marra, L. Galfetti, F. Severini, L. De Luca, Materials Science and Engineering C 2007, 27, 1393). All these methods produce powders consisting of agglomerated nanoparticles that are impossible to re-disperse by any known method when combining with a polymer (C. E. Johnson, S. Fallis, A. P. Chafin, T. J. Groshens, K. T. Higa, I. M. K. Ismail, T. W. Hawkins, Journal of Propulsion and Power 2007, 23, 669-682). The prior art suffered from the disadvantage that it is not able to achieve the requisite composition homogeneity and uniform, unagglomerated dispersions of primary nanoparticles, especially when the particle size ranges are very small (<100 nm).
Another prior art production method is known from US Patent Application Publication No. US 2013/0317170 A1, Marks et al (2013) (“Marks”). Marks discloses a composite comprised of a polyolefin polymer filled with aluminum nanoparticles with an aluminum oxide coating. Mark's composite is produced by an in-situ polymerization technique, in which a commercially available aluminum nanoparticle powder (with native oxide coating) is functionalized with a polymerization catalyst, after which propylene is polymerized around the functionalized particles, in so forming the composite of aluminum in polypropylene. Marks uses terms such as “homogeneous” and “well dispersed” in describing the dispersion of aluminum nanoparticles in their disclosed composite but does not disclose a composition of dispersed primary nanoparticles of aluminum. This fact is made clear in
The small particle size and high surface-to-volume ratio of aluminum nanopowders presents major processing challenges. When these fine powders are combined with the polymer binders and other ingredients typically used in energetic formulations (fuels, propellants, explosives), the mixture viscosity becomes too high to process. One approach that has been attempted to overcome this problem is to process the aluminum nanoparticles into agglomerates that are much larger than the sizes of the primary nanoparticles, for example, agglomerates that are several micrometers or larger in diameter. Such large agglomerates may have processing characteristics similar to those of conventional micrometer-sized aluminum powders. Polymer binders and other ingredients have been combined with the aluminum nanoparticles during the controlled agglomeration process to produce powders of composite compositions. Examples of these methods in the prior art include H. Wang, G. Jian, S. Yan, J. B. DeLisio, C. Huang, and M. R. Zachariah, ACS Applied Materials & Interfaces, 2013, 5, 6797-6801, and R. J. Jacob, B. Wei, M. R. Zachariah, Combustion and Flame, 2016, 167, 472-480.
These examples used commercially available aluminum nanopowder as their starting material, which was combined with a solvent with various methods such as stirring and sonication applied to partially disperse the powders, and then an electrospray procedure was used to evaporate the solvent and produce the powder. The powders described by these examples are porous in nature, meaning that they have a large amount of internal porosity and void space within the powders (i.e. the nanoparticle agglomerates). Porous powders are potentially problematic for use in energetic formulations in which a maximum mass density or energy density is desired. The volumetric loading of aluminum (meaning the mass of aluminum per unit volume) in a formulation using such powders will be limited due to the porous nature of the particles. The porous nature of these powders is due to use of aluminum nanopowder as a starting material. As noted above, aluminum nanopowder inherently consists of agglomerates of aluminum nanoparticles, and the agglomerates cannot be broken up and dispersed into unagglomerated primary nanoparticles. The formation of these agglomerated nanoparticles into larger, micrometer-sized secondary agglomerates inherently creates a porous material because the individual primary nanoparticles are not freely mobile (being strongly attached to neighboring particles) and therefore cannot rearrange themselves into a closely packed, densified structure during the formation of the larger micrometer-sized secondary agglomerates (for example, during the electrospray process). Non-porous, micrometer-sized agglomerates of primary aluminum nanoparticles, and methods to produce such powders, would have significant advantages over the prior art. Another disadvantage of these examples is that the aluminum nanopowder used as starting materials contains only around 70% active aluminum (meaning aluminum in its metallic form) due to the presence of the native oxide coating on the particles. Compositions with higher active aluminum content, and methods to produce such compositions, would be advantageous over the prior art.
U.S. Pat. No. 9,573,857 B2, Reid et al. (2017) (“Reid”) describes a method to synthesize nanoparticles of aluminum beginning with a molecular precursor of aluminum such as an amine adduct of alane, and combining it with a polymer such as hydroxyl terminated polybutadiene (HTPB), to which has been bonded an organometallic complex that acts as a catalyst to decompose the aluminum precursor. Upon combining the aluminum precursor with the catalyst-functionalized polymer, the precursor decomposes to form metallic aluminum particle nuclei, which, as they form, become coated with the catalyst-attached polymer molecules. This reaction mechanism, involving the simultaneous formation of aluminum particle nuclei by action of the catalyst and their coating with the polymer to which the catalyst is attached, produces a composite material containing dispersed primary nanoparticles of aluminum, which can be used as a binder component in a propellant or explosive, in which the rapid combustion of the dispersed primary aluminum nanoparticles increases the propellant or explosive performance. The aluminum nanoparticles formed by this method can be made nearly free of any native-oxide coating.
One deficiency of Reid is that it does not teach powder compositions or methods for producing powders. Reid teaches non-powder solids and describes their applications as binders in solid fuels, propellants, and explosives. Reid also teaches liquid fuels. Many energetic formulations require components (sometimes called ingredients) that are used in powder form during energetic manufacturing processes such as explosive or propellant mixing, and are present in the resulting energetic composition in the form of a powder that is surrounded by a binder and/or intermixed with other powders.
Accordingly, a combustible composite powder which overcomes the shortcomings of the prior art is desired.
A powder comprising primary nanoparticles of aluminum and/or aluminum oxide that are physically separated from one another by an intervening organic or polymeric material and formed into secondary particles that are substantially larger than the primary nanoparticles.
The features and advantages of the present invention will become more readily apparent from the following detailed description of the invention in which like elements are labeled similarly and in which:
Disclosed embodiments in this Disclosure are described with reference to the attached figures, wherein like reference numerals are used throughout the figures to designate similar or equivalent elements. The figures are not drawn to scale and they are provided merely to illustrate the disclosed embodiments. Several aspects are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the disclosed embodiments. One having ordinary skill in the relevant art, however, will readily recognize that the subject matter disclosed herein can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring structures or operations that are not well-known. This Disclosure is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with this Disclosure.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of this Disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5.
Disclosed embodiments include powders comprising primary nanoparticles of aluminum, aluminum oxide, aluminum coated with a surface oxide layer, or combinations of these materials, which are separated from each other by an organic or polymer material, and which are agglomerated into secondary particles substantially larger than the primary nanoparticles.
For the purpose of this disclosure, the term “primary nanoparticle” means a particle less than 200 nanometers in diameter that is the smallest discrete identifiable entity observable by transmission electron microscopy, and excludes aggregates or agglomerates of such particles. The terms “aggregate” and “agglomerate”, which are often used interchangeably in the field of materials science, mean clusters of more than one primary particle, which are held together by physical or chemical interactions. The primary nanoparticle may be a homogeneous particle composed of a single type of material (i.e. of uniform chemical composition), or it may contain more than one type of material, such as an aluminum oxide layer on the surface of an aluminum particle, or organic molecules chemically bonded to the surface of an inorganic particle. Two or more primary nanoparticles that are separated from each other by a dissimilar material are not considered to be aggregated or agglomerated, i.e., they are unagglomerated.
In describing the microstructure of composites, especially composites containing nanoparticles, terms such as “homogeneous” and “uniform” are commonly used in the academic and patent literature to describe the quality of dispersion of particles in their surrounding medium. In the inventor's review of the literature, we find these terms to be problematic in describing the microstructure of the subject composites. These terms are problematic because they are subjective, with meanings that change based on the context and size regimes being described. For clarity in this disclosure, the inventors therefore use the term “dispersed primary nanoparticles” to differentiate between the microstructures of the disclosed compositions and those of prior art describing uniform or homogeneous particle dispersions at various context size scales, which may contain dispersed nanoparticle aggregates or agglomerates, but which do not contain dispersed primary nanoparticles.
Some of the disclosed embodiments are powders. For the purpose of this disclosure, each powder particle of the subject invention is called a “secondary particle” in order to distinguish it from the primary nanoparticles contained within the secondary particle. The primary nanoparticles described in this invention are composed of materials including aluminum, aluminum oxide, aluminum coated with aluminum oxide (i.e. the native oxide of aluminum), or aluminum coated with a different type of molecule called a passivating molecule. The passivating molecule can by any compound that forms a chemical bond with aluminum or aluminum oxide. These compounds include carboxylic acids, alcohols, ketones, diketones, aldehydes, epoxy compounds, and silanes. The polymeric or organic component of the subject invention can also be considered a passivating molecule if the molecules of that component are chemically bonded or physically adsorbed to the primary nanoparticles. The size range of the primary nanoparticles is typically less than 200 nm in diameter, and preferably less than 50 nm in diameter.
A powder is differentiated from a continuous solid by a few characteristics. One characteristic is the size of the particles of the powder, which is generally from a few millimeters (coarse powder) to sub-micrometer (fine powder) in size. Another characteristic is that, when placed in a container, the powder will move or flow when the container is tilted and can be poured out of the container. A third characteristic is present when the powder is incorporated into a larger material formulation, in which it is common for the particles of powder to be dispersed as discrete particles within a continuous phase or binder. In some industries, common terminology refers to powders as fillers or solids, and the continuous phase in which the powder is dispersed as a binder or matrix.
The material that separates each primary nanoparticle from the other includes at least one type of organic or polymeric material. Polymeric materials include carbon-based polymers (organic polymers) and silicon-based polymers (inorganic polymers, such as silicones or polysiloxanes). Examples of organic materials include, but are not limited to, waxes, polypropylene, polyethylene terephthalate, polyvinylidene fluoride, polycarbonates, fluoropolymers, polyethylene glycol, polycaprolactone, cellulose acetate butyrate, polyimides, polystyrene, poly (ether ether ketone), polybutadiene, hydroxyl terminated polybutadiene (HTPB), polyphenylene sulphide, acrylonitrile butadiene styrene, polybutadiene acrylonitrile (PBAN), polybutadiene acrylic acid (PBAA), carboxyl terminated polybutadiene (CTPB), polyglycidyl nitrate (PGN), glycidyl azide polymer (GAP), poly(3,3-bis(azidomethyl) Oxetane) Poly(BAMO), poly(3-azidomethyl 3-methyl oxetane) Poly(AMMO), and poly(3-nitratomethyl methyl oxetane) poly(NIMMO) and polysiloxanes.
In another embodiment of this material, the polymer, silicone, or organic component is removed during processing of the material, such as by thermal decomposition, leaving behind a different type of insulating material (for example, a carbonaceous material derived from the decomposition of a polymer), or oxides of aluminum or of a different metal, or pores or voids. In this embodiment, the primary aluminum nanoparticles are separated and electrically isolated from one another by one or more of these different types of insulating materials.
The novel characteristic of each of these embodiments is a composition that includes unagglomerated primary nanoparticles of aluminum or aluminum oxide, which are separated from one another by at least one type of polymeric or organic material. The unaggregated and unagglomerated nature of the primary nanoparticles in the composite powder's secondary particles is responsible for the favorable properties of the material.
To overcome the problem of primary nanoparticle agglomeration in aluminum nanoparticle powders, the inventors looked to a method previously developed to produce aluminum nanoparticle polymer composites for propellant and explosive applications. U.S. Pat. No. 9,573,857 B2, Reid et al. (2017) (“Reid”) describes a method to synthesize nanoparticles of aluminum beginning with a molecular precursor of aluminum such as an amine adduct of alane, and combining it with a polymer such as hydroxyl terminated polybutadiene (HTPB), to which has been bonded an organometallic complex that acts as a catalyst to decompose the aluminum precursor. Upon combining the aluminum precursor with the catalyst-functionalized polymer, the precursor decomposes to form metallic aluminum particle nuclei, which as they form become coated with the catalyst-attached polymer molecules. This reaction mechanism, involving the simultaneous formation of aluminum particle nuclei by action of the catalyst and their coating with the polymer to which the catalyst is attached, produces a composite material containing dispersed primary nanoparticles of aluminum as a binder component in a propellant or explosive, in which the rapid combustion of the dispersed primary aluminum nanoparticles increases the propellant or explosive performance.
The present invention uses composites containing up to approximately 95 percent aluminum by mass, which is much higher than the concentrations of aluminum envisioned for use in a polymer binder, which generally is required to have liquid or flowable characteristics during the propellant mixing process.
The present invention is produced using a process generally categorized into two steps. In the first step, a powder precursor solution is prepared. The precursor solution contains at least three components: unagglomerated primary nanoparticles of aluminum, at least one kind of dissolved organic or polymeric material, and a volatile solvent (meaning a solvent that can be removed by evaporation). The dissolved organic or polymeric material(s) may be chemically or physically adsorbed to the surface of the primary nanoparticles of aluminum, or may be freely dissolved in the solvent (unbonded to the primary nanoparticles of aluminum), or a combination of these. The precursor solution may contain other ingredients such as passivating compounds, polymer curing agents, other types of particles, and additives such as surfactants to improve particle stability in the suspension and prevent sedimentation. Trace compounds and impurities from synthesis biproducts may also be present in the solution.
As described above, this first step of preparing the precursor solution can be prepared by the methods described in Reid. Reid teaches the synthesis of nanoparticles of aluminum beginning with a molecular precursor of aluminum such as an amine adduct of alane, and combining it with a polymer such as hydroxyl terminated polybutadiene (HTPB), to which has been bonded an organometallic complex that acts as a catalyst to decompose the aluminum precursor to produce unagglomerated primary nanoparticles of aluminum. Each of these components can be dissolved in a volatile solvent, or mixture of solvents, which facilitates the chemical reactions described therein. One convenient solvent is toluene. The reactions are typically performed in an apparatus filled with an inert gas atmosphere such as argon to prevent oxidation of the air-sensitive materials like aluminum. The present inventors discovered that, because this method produces unagglomerated primary nanoparticles of aluminum, which are homogeneously dissolved, together with a dissolved organic or polymeric material, in a solvent that can subsequently be removed by evaporation, that a subsequent step can be added to this method, which processes the precursor solution into a powder of the compositions and characteristics described in this invention. The discovery that powders with the described favorable characteristics can be produced by the methods described in this invention is an advancement over the prior art. The prior art does not teach the formation of powders by these methods and does not anticipate that such powders would have the favorable characteristics described in this invention.
In one embodiment of the present invention, the ratios of reaction ingredients is such that aluminum constitutes a majority of the total mass of the composition except for the solvent. Less than majority aluminum compositions may also be used, if the application warrants a lower aluminum content, and if the composition creates a material with a predominantly solid characteristic, so that it can be formed into a powder. Examples of compositions that have predominantly solid characteristics, as opposed to liquids that could not be processed into a powder, include those in which the organic or polymeric constituent is a solid itself, and provides the solid characteristic necessary for the composition to be a solid in the powder form, and those in which the organic or polymeric constituent is a liquid, gel, or soft phase that could not be processed into a powder, but the total composition contains a sufficient concentration of primary nanoparticles of aluminum such that the composition is a solid and can be processed into a powder.
Upon completion of the aluminum nanoparticle synthesis reaction and preparation of the powder precursor solution, the second step in the production of the present invention is to remove the solvent by a method that results in the formation of a powder, or a solid that can be subsequently processed into a powder. The formation of a powder with the characteristics described in this invention is one aspect that differentiates the present invention from the prior art. A significant discovery by the current inventors was that the described precursor solution is capable of forming powders that have desirable characteristics such as having little or no internal void space (i.e. having full or nearly full density). The solvent removal step is typically performed by evaporation. If the absence of aluminum oxide is desired, the evaporation can be performed in an air and water-free environment, such as a container or chamber filled with inert gas. Solvent evaporation may be performed using a wide range of techniques. One particularly suitable evaporation technique is spray drying. This technique feeds the precursor solution through a nozzle, which sprays warm droplets of the solution into an evaporation chamber. As the solvent evaporates, the solute components in the droplet coalesce into a solid particle. The spray drying process generally includes a particle collection technique such as a cyclone. The spray drying operation can be performed using inert gas filled equipment to prevent aluminum oxidation. The collected particles are the secondary particles described in this disclosure, which contain within the primary nanoparticles of aluminum and the organic and/or polymeric constituents.
Other powder formation methods have been demonstrated as the second step in the production process. For example, the solution can be cast into a film or boiled to dryness under vacuum to yield a solid residue, followed by mechanical grinding or milling to produce a powder. Other powder formation methods may be used, including but not limited to freeze drying (also known as lyphilization) and electrospraying. The powder can range in sizes from coarse (up to several millimeters in average particle diameter) to fine (1 micrometer average particle diameter or smaller). Films, flakes, and other solid material morphologies can be prepared by these methods.
The total solute content of the precursor solution is generally around 0.1-20% by mass, but is only limited by the solubility limits of the constituents. In one embodiment, the precursor solution contains types of particles in addition to the aluminum nanoparticles. Examples of additional types of particles or other dissolved substances that include but are not limited to oxidizers, explosives, polymers or polymer particles such as fine particles of fluoropolymers, particles of other types of metals, larger particles of aluminum including particles larger than 100 nm in diameter, and metal-oxides such as iron oxide or copper oxide. These additional particles or dissolved substances may be of a type that reacts with aluminum at elevated temperatures to liberate heat. When these additional particles or dissolved substances are included in the precursor solution, they become intermixed with the primary nanoparticles of aluminum or aluminum oxide in the secondary particles of the resulting powder. In this embodiment, the composition of the powder includes one or more of these additional types of particles or substances as a component of the secondary particles.
Key features of the present invention, which when combined distinguish it from the prior art, include:
The unique composition of the powder, in which each primary nanoparticle of aluminum is separated from the others by an intervening organic or polymeric material, produces favorable combustion properties when the powder is used in a propellant, explosive, fuel, or other energetic material or application. Although precise mechanisms are difficult to discern under relevant combustion environments, based on combustion rate measurements, the authors propose that as the secondary particles are heated to the oxidation or decomposition temperature of the organic or polymer phase, those components rapidly expand and decompose to yield vapor decomposition and/or oxidation products. This gas formation breaks apart the secondary particles and exposes their internal surface area, including the primary nanoparticles, to the oxidizing environment, in which they rapidly react. Because of this advantageous composition, this powder improves combustion performance in several ways over conventional aluminum ingredients:
Disclosed embodiments include composite solid propellants containing a powder comprising primary nanoparticles of aluminum separated from one another by an intervening organic or polymeric material, a solid oxidizing agent, and a polymer binder. The propellants may additionally contain other types of metal particles including aluminum powder, boron, and magnesium, various curatives including diisocyanates, various plasticizers, bonding agents, catalysts such as iron oxide, copper oxide, aluminum oxide, or titanium oxide, antioxidants, and other ingredients known to the propellant and explosive trades. Energetic ingredients including explosives such as RDX, HMX, and CL-20, may be included. Many ingredients may optionally be included in the propellants, such as those known in the prior art to affect mechanical properties, aging characteristics, temperature response, and performance.
In experiments conducted by the present inventors, the methods described by Reid were used to produce a toluene solution with the following approximate composition: 1.8 g/mL aluminum nanoparticles, 0.39 g/mL HTPB R45M, and 0.093 g/mL acetylacetone, which was produced and stored in argon filled vessels. This solution was processed into a powder by spray drying using argon carrier gas. The spray drying system was equipped with an inert gas loop to maintain an air-free environment within the dryer, and a system to condense and capture the flammable solvent. The powder was collected and analyzed. The powder was stable in air upon removal from the spray dryer. The active aluminum content of the powder was calculated by measuring the volume of hydrogen gas evolved by the reaction of aluminum with aqueous sodium hydroxide. The reaction is 2 Al+2 NaOH+2 H2O→2 NaAlO2+3H2. By this method, only the “active”, unoxidized aluminum content is measured. Aluminum oxide or hydroxide do not contribute to the evolved hydrogen gas reaction. The active aluminum concentration was measured to be 78.5% by mass. The density, as measured by liquid pycnometry, was measured to be 1.918 g/cc, which closely matches the theoretical density of 1.909 g/cc for the composition of 78.5% aluminum and 21.5% HTPB. The closeness in match between the measured and theoretical density implies that nearly 100% of the aluminum present in the powder is active (i.e. in its unoxidized state).
In a typical experiment, three composite solid propellants were prepared and propellant burning rates were measured. Propellants were made with HTPB R45M binder containing 73% ammonium perchlorate, 10% aluminum, 2% DOA plasticizer, and minor ingredients and additives. Propellant 1 contained H5 grade micron aluminum powder. Propellant 2 contained the present invention powder made by a method of film casting, then drying, then grinding to form a coarse powder with secondary particle sizes of approximately 50-1000 micrometers. Propellant 3 contained the present invention powder made by a spray drying method to produce a fine powder with secondary particle sizes of approximately 1-15 micrometers. Strand burner testing of the burning rates of propellants 1, 2, and 3 found that propellants containing the present invention (propellants 2 and 3) had increased burning rates compared to propellants containing an equivalent amount of micrometric aluminum powder (propellant 1). The burning rates of propellants 2 and 3 were only slightly different, meaning that burning rates are only slightly affected by the secondary particle size (coarse or fine) of the current invention, which provides evidence that the secondary particles break apart during combustion and thus the originating particle size has little effect on the reaction rate.
As seen in
While various disclosed embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Numerous changes to the subject matter disclosed herein can be made in accordance with this Disclosure without departing from the spirit or scope of this Disclosure. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.
Thus, the breadth and scope of the subject matter provided in this Disclosure should not be limited by any of the above explicitly described embodiments. Rather, the scope of this Disclosure should be defined in accordance with the following claims and their equivalents.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
This application claims the benefit of U.S. Provisional Application No. 63/345,949 filed on May 26, 2022. The entire contents of these applications are incorporated herein by reference in their entirety.
The subject invention was made with U.S. Government support under Contract No. HQ014718C7437 with the Missile Defense Agency. The U.S. Government has certain rights in this invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2023/023668 | 5/26/2023 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63345949 | May 2022 | US |
