Encapsulated, particulate energetic composition and the making of same

Abstract

An encapsulated, particulate energetic composition includes one of explosive particles of a known size, oxidizer particles of a known size, and a mixture of explosive particles and oxidizer particles of known sizes, in which particles of one of the explosive particles, the oxidizer particles, and the mixture of the explosive and the oxidizer particles, are encapsulated by a combustible fuel of a known thickness to enhance the energy output. A method of making the encapsulated, particulate energetic composition includes placing one of explosive particles, oxidizer particles, and a mixture of explosive particles and oxidizer particles within a deposition chamber, mixing one of the explosive particles, the oxidizer particles, and the mixture of explosive particles and the oxidizer particles, and depositing, to a known encapsulating thickness, a combustible fuel onto the one of the explosive particles, the oxidizer particles, and the mixture of explosive particles and oxidizer.

Claims

1. An encapsulated, particulate energetic composition, consisting of: one of explosive particles of a known size, oxidizer particles of a known size, and a mixture of explosive particles and oxidizer particles, wherein said one of said explosive particles each comprises a particle surface, wherein said explosive particles and said oxidizer particles of said mixture are of known sizes, wherein particles of said one of said explosive particles, said oxidizer particles and said mixture of explosive particles and oxidizer particles, are encapsulated by a known thickness of a combustible fuel, wherein a thin film of the combustible fuel is bonded to said particle surface through a reaction to encapsulate said one of said explosive particles, said oxidizer particles and said mixture of explosive particles and oxidizer particles where the thin film is immediately adjacent the particle surface, which is encapsulated, and wherein said know thickness of the thin film is directly deposited and directly bonded to the particle surface absent an intermediate layer between the thin film and the particle surface using a sputtering process in order to form the encapsulated, particulate energy composition, and wherein the combustible fuel is one of a combustible metal and a combustible metal oxide.

2. The encapsulated, particulate energetic composition of claim 1, wherein said explosive particles comprise any of 1,3,5-trinitro-1,3,5-triazinan (RDX), 1,3,5,7-tetranitroperhydro-1,3,5, 7-tetrazocine (HMX), 2,4,6,8,10,12-hexanitro 2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), 2-methyl-1,3,5-trinitrobenzene (TNT), 2,4,6-trinitrophenyl-N-methlynitramine (Tetryl), 1,3,5-trinitro-2-[2-(2,4,6-trinitrophenyl)ethenyl]benzene (HNS), 3-nitro-1,2, triazol-5-one (NTO), 1,3,3-trinitroazetidine (TNAZ), nitroguanidine (NQ), tetrazine dioxide (TDO), 2,4,6-trinitrobenzene (TNB), 2,4,6-trinitropyridine (TNPy), 2,4,6-trinitropyridine-N-oxide (TNPyOx) 2,6-diazido-4-nitro-pyridine-N-oxide (DazN-PyOX), triaminoguanidinium azotetrazolate (TAGAZ), diamino azobis tetrazine (DAAT), 2,5-diamino-3,6-dinitropyrazine (ANPZ-i), 2,6-diamino-3,5-dinitropyridine-1-oxide (ANPyO), 2,6-diamino-3,5-dinitropyridine (ANPy), 2,6-bis(picrylamino)-3,5 dinitropyridine (PYX), 2,4-dinitroimidazole (DNI), 1,1-diamino-2,2-dinitroethylene (DADNE or FOX-2,6-diamino-3,5-dinitropyrazine (ANPZ), 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), 1,3-dinnitrato-2,2-bis(nitratomethyl)propane (PETN), 4,1O-Dinitro-2,6,8,12-tetraoxa-4, 10-diaza-tetracyclododecane (TEX), ammonium dinitramide (AND), 1-amino-2,4,6-trinitrobenzene (MATB), 1,3-diamino-2,4,6-trinitrobenzene (DATB), 1,3 diazido-2-nitrazapropane (DANP), 1,5 diazido-2,4-nitrazapentane (DADZP), 1,7 diazido-2,4,6-trinitrazaheptane (DATH), n-propyl azidoethyl nitramine (Pr NENEA), and 1,3,5 triamino-2,4,6-trinitrobenzene (TATB).

3. The encapsulated, particulate energetic composition of claim 1, wherein said oxidizer particles comprise any of potassium nitrate, sodium nitrate, ammonium nitrate, potassium perchlorate, sodium perchlorate, ammonium perchlorate, lithium perchlorate, nitronium perchlorate, ammonium dinitramide, hydrazinium nitroformate, and phosphorus pentoxide.

4. The encapsulated, particulate energetic composition of claim 1, wherein said combustible fuel comprises any of aluminum, copper, iron, tungsten, hafnium, tantalum, magnesium, nickel, sodium, molybdenum, potassium, phosphorous, silicon, boron, aluminum oxide, copper oxide, iron oxide, tungsten hafnium oxide, tantalum oxide, magnesium oxide, nickel oxide, sodium monoxide, molybdenum oxides, potassium oxide, boron oxides, and silicon oxides.

5. The encapsulated, particulate energetic composition of claim 1, wherein said known size of said explosive particles, said known size of said oxidizer particles, and said known sizes of said explosive particles and said oxidizer particles in said mixture ranges from 0.1 microns diameter to 1 centimeter diameter.

6. The encapsulated, particulate energetic composition of claim 1, wherein said known thickness of a combustible fuel is greater than 1 nanometer.

7. The encapsulated, particulate energetic composition of claim 1, further comprising any of a combustion catalyst, a desensitizer, a plasticizer, and a wetting agent.

8. An encapsulated, particulate energetic composition, consisting of: one of explosive particles of a known size, oxidizer particles of a known size, d a mixture of explosive particles and oxidizer particles, wherein said one of said explosive particles and said oxidizer particles being of known sizes, wherein particles of said one of explosive particles, said oxidizer particles, said mixture of explosive particles and oxidizer particles, are and encapsulated a by known thickness of one of a combustible metal oxide fuel, and a combustible metal fuel and the combustible metal oxide fuel, wherein a thin film of said one of said combustible metal oxide fuel, an said combustible metal fuel and said combustible metal oxide fuel, is bonded to said particle surface through a reaction to encapsulate said one of said explosive particles, said oxidizer particles and said mixture of explosive particles and oxidizer particles where the thin film is immediately adjacent the particle surface, which is encapsulated, and said known thickness of the thin film is formed from a continuous sputtering deposition process, wherein said known thickness of the thin film is directly deposited and directly bonded to the particle surface using a continuous sputtering deposition process absent an intermediate layer between the thin film and the particle surface in order to form the encapsulated, particulate energy composition.

9. The encapsulated, particulate energetic composition of claim 1, wherein the encapsulated, particulate energetic composition includes the explosive particle comprised of RDX crystals and the combustible fuel comprised of aluminum, wherein a bond exists between a nitro group of the RDX crystals and the aluminum, and wherein a N 1s x-ray photoelectron spectrum of the bond includes the nitro group peak of the RDX crystal is diminished in intensity relative to a ring structure peak of the RDX crystal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the present invention are discussed herein in reference to the drawings, in which:

(2) FIG. 1 illustrates a wide-scan X-ray photoelectron spectrum of 1,3,5-trinitro-1,3,5-triazinane (RDX) explosive particles for the C 1s, N 1s, O 1s regions of RDX explosive particles, and a detailed view of the N 1s region, which identified changes to the chemical state of the RDX as relates to the nitro group and the ring structure, in an exemplary embodiment of the present invention; and

(3) FIG. 2 illustrates a wide-scan X-ray photoelectron spectrum of RDX explosive particles following aluminum sputter deposition, in which the nitrogen peak associated with the nitro group was diminished compared to that of the ring structure, indicating a preferential reaction of the nitro group of the RDX to the aluminum deposition, while leaving the ring structure intact structure, in an exemplary embodiment of the present invention;

(4) FIG. 3 illustrates a schematic diagram of a sputtering system used for the physical deposition of an encapsulating combustible fuel on explosive and/or oxidizer particles of an encapsulated, particulate energetic composition in an exemplary embodiment of the present invention; and

(5) FIG. 4 illustrates a flow diagram of a method of making an encapsulated, particulate energetic composition in an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(6) An exemplary embodiment of the encapsulated, particulate energetic composition of the present invention may include explosive particles of a known size, oxidizer particles of a known size, and/or a mixture of explosive and oxidizer particles of known sizes, each of the explosive and/or oxidizer particles being encapsulated by a combustible fuel of a known thickness.

(7) The explosive particles may include any of nitramines, sometimes referred to as nitroamines, for example, 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitroperhydro-1,3,5,7-tetrazocine (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), and other energetic compounds, for example, 2-methyl-1,3,5-trinitrobenzene (TNT), 2,4,6-trinitrophenyl-N-methlynitramine (Tetryl), 1,3,5-trinitro-2-[2-(2,4,6-trinitrophenyl)ethenyl]benzene (HNS), 3-nitro-1,2,4-triazol-5-one (NTO), 1,3,3-trinitroazetidine (TNAZ), nitroguanidine (NQ), tetrazine dioxide (TDO), 2,4,6-trinitrobenzene (TNB), 2,4,6-trinitropyridine (TNPy), 2,4,6-trinitropyridine-N-oxide (TNPyOx), 2,6-diazido-4-nitro-pyridine-N-oxide (DazN-PyOX), triaminoguanidinium azotetrazolate (TAGAZ), diamino azobis tetrazine (DAAT), 2,5-diamino-3,6-dinitropyrazine (ANPZ-i), 2,6-diamino-3,5-dinitropyridine-l-oxide (ANPyO), 2,6-diamino-3,5-dinitropyridine (ANPy), 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), 2,4-dinitroimidazole (DNI), 1,1-diamino-2,2-dinitroethylene (DADNE or FOX-7), 2,6-diamino-3,5-dinitropyrazine (ANPZ), 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), 1,3-dinnitrato-2,2-bis(nitratomethyl)propane (PETN), 4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diaza-tetracyclododecane (TEX), ammonium dinitramide (AND), 1-amino-2,4,6-trinitrobenzene (MATB), 1,3-diamino-2,4,6-trinitrobenzene (DATB), 1,3 diazido-2-nitrazapropane (DANP), 1,5 diazido-2,4-nitrazapentane (DADZP), 1,7 diazido-2,4,6-trinitrazaheptane (DATH), n-propyl azidoethyl nitramine (Pr NENEA) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in an exemplary embodiment of the invention. In an exemplary embodiment of the invention, the explosive particles may comprise a crystal of an explosive material or a polycrystalline structure of the explosive material.

(8) In an exemplary embodiment of the invention, the oxidizer particles may include any of potassium nitrate, sodium nitrate, ammonium nitrate, potassium perchlorate, sodium perchlorate, ammonium perchlorate, lithium perchlorate, nitronium perchlorate, ammonium dinitramide, hydrazinium nitroformate, and phosphorus pentoxide. In an exemplary embodiment of the invention, the oxidizer particle may comprise a crystal of an oxidizer material or a polycrystalline structure. In an exemplary embodiment of the invention, the oxidizer particles may include a crystal of an oxidizer material or a polycrystalline structure of the oxidizer material.

(9) In an exemplary embodiment of the invention, an encapsulating thickness of combustible fuel may include a combustible metal, for example, any of aluminum, copper, iron, tungsten, hafnium, tantalum, magnesium, nickel, sodium, molybdenum, and potassium, or a non-metal, for example, any of phosphorous, silicon, and boron. The combustible fuel may also include a metal oxide, for example, any of aluminum oxide, copper oxide, iron oxide, tungsten oxide, hafnium oxide, tantalum oxide, magnesium oxide, nickel oxide, sodium monoxide, molybdenum oxides, and potassium oxide, or a non-metal oxide, for example, any of boron oxides and silicon oxides.

(10) Experimental (Actual) Methodology:

(11) The RDX explosive crystals of a known size, i.e., 150 to 300 microns diameter, were commercially obtained from BAE Systems, Ordnance Systems Inc., Holston Army Ammunition Plant, Kingsport Tenn. Alternatively, a known size of explosive particles may be obtained by sieving, recrystallization, and/or milling explosive particles to obtain a known size of explosive particles.

(12) Similarly, oxidizer particles of a known size (distribution) may be obtained commercially or may be sieved, recrystallized, and/or milled to obtain a known size of oxidizer particles.

(13) Sputtering of aluminum onto RDX crystals was accomplished in an ultra high vacuum (UHV) apparatus. Sputtering is a physical vapor deposition technique used to deposit thin films of a material onto an RDX crystal. A gaseous plasma of argon gas was created in the sputtering chamber and the plasma ions were accelerated onto a target material of aluminum. The target material was eroded by the arriving plasma ions, via energy transfer, and was ejected in the form of neutral particles, that is, individual aluminum atoms or clusters of aluminum atoms. An energy source, for example, RF, DC, or microwave, was used to initiate and maintain the plasma state. This dynamic condition was created by metering argon gas into a pre-pumped vacuum chamber and allowing the chamber pressure to reach a specific level, for example, 0.01 Torr, and by introducing a live electrode into this low pressure gas environment using a vacuum feedthrough.

(14) To overcome the two main problems of conventional sputtering, that is, overheating and structural damage to the target by electron bombardment, and a slow deposition rate, the inventor also used the technique of magnetron sputtering. Magnetron sputtering uses magnets behind the target to create strong electric and magnetic fields. These fields trap electrons directly above the target surface, where they are less likely to bombard the target. Instead, the electrons follow helical paths around the magnetic field lines, providing more ionizing collisions with neutral gaseous particles, for example, argon, near the target surface than would otherwise occur. The extra argon ions created as a result of these collisions lead to a higher deposition rate of the target atoms.

(15) Magnetron sputtering has proven extremely beneficial in the semiconductor industry for the deposition of two dimensional thin films. In an exemplary embodiment of the invention, encapsulation of the particle surfaces of the explosive material, RDX, with aluminum was accomplished by the mixing and/or agitation of the RDX explosive particles within the magnetron sputtering chamber. As is known to one of ordinary skill in the art, the degree of encapsulation of each individual RDX particle varies with inter alia the deposition rate of the aluminum, the exposure time of individual surfaces of the RDX particles to the deposited aluminum, the amount of mixing, and the time of aluminum deposition. Effective encapsulation of the RDX particles by magnetron sputtering was determined by microscopic visualization of the encapsulated RDX particles, which showed a homogeneous metallic encapsulation of the RDX particles.

(16) Referring to FIG. 3, sample particles 2, that is, RDX explosive particles of 150-300 microns diameter were effectively encapsulated by magnetron sputtering of an aluminum target when the RDX explosive particles were rotated within a sample cup 4 of a magnetron sputtering chamber 6. The sample cup 4, containing the RDX explosive articles 2, was positioned at an angle with respect to the gravitational force in an exemplary embodiment of the invention. The RDX explosive particles 2 were rotated in the sample cup at a rate of approximately or about 0-20 rotations per minute in an exemplary embodiment of the invention. In various exemplary embodiments, the sample cup 4 may also be cooled 8, for example, through the use of air, gas, liquid nitrogen, or water. In an exemplary embodiment of the invention, an effective angle (Angle.sub.1) and rotation rate (R) were empirically selected to cause the RDX explosive particles to slip or fall within the rotating sample cup 4, to create the desired mixing of the RDX explosive particles. In various exemplary embodiments of the invention, mixing of the explosive particles may be enhanced by vibrating via a vibration mechanism 12 the rotating sample cup 4 or by introduction of a stirrer 12, while the sample cup is rotating. The stirrer may, for example, be attached to a linear feedthrough of the magnetron sputtering chamber, which allows for the adjustment in its position with respect to the sample cup. Additionally, the introduction of inert materials, which were of a larger size than the RDX explosive particles and which could tumble inside the rotating sample cup, was also found useful in enhancing the mixing of the RDX explosive particles in an exemplary embodiment of the invention. Alternatively, other particulate mixing processes well known to those in the art may be used.

(17) Similarly, in various exemplary embodiments of the invention, oxidizer particles of a known size (distribution) or a mixture of explosive and oxidizer particles of known sizes (distribution) may be encapsulated by a combustible fuel to a known thickness by magnetron sputtering, when the oxidizer particles or the mixture of explosive and oxidizer particles is rotated within the sample cup of the magnetron sputtering chamber. In addition, the sample cup containing the oxidizer particles or a mixture of explosive and oxidizer particles may be positioned at a known angle with respect to the gravitational force, rotated at a known rate of rotation, and/or cooled in various exemplary embodiments of the invention. Likewise, mixing of the oxidizer particles or a mixture of explosive and oxidizer particles, contained in the sample cup, may be enhanced by vibrating the rotating sample cup, introducing a stirrer while the sample cup is rotating, or introducing large inert particles, which may tumble inside the rotating sample cup. Alternatively, other particulate mixing processes well known to those in the art may be used.

(18) Experimentally, the positioning of the sample cup, containing the RDX explosive particles, relative to the aluminum target 14 was found to affect, greatly, the deposition rate of the aluminum onto the RDX explosive particles. In the present experiment, the height (Position.sub.1) and angle (Angle.sub.1) of the sample cup, containing the RDX explosive particles, and the position (Position.sub.2) and angle (Angle.sub.2) of the aluminum target could be adjusted with respect to the magnetron sputtering chamber. In various exemplary embodiments, empirically adjusting the positions and angles of the combustible fuel target and the sample cup, containing explosive particles, oxidizer particles, and/or a mixture of explosive and oxidizer particles, may be used to adjust deposition rates of the combustible fuel material on the explosive particles, oxidizer particles, or a mixture of explosive and oxidizer particles.

(19) Experimental (Actual) Analysis:

(20) The experimental analysis of the aluminum encapsulated RDX crystals was performed in a stainless steel UHV chamber with a working base pressure of 110.sup.10 Torr. The UHV chamber contained, among other things, a hemispherical analyzer used in concert with a dual Al/Mg K.sub. X-ray source for X-ray photoelectron spectroscopy (XPS), and a quadrupole mass spectrometer for residual gas analysis. The thickness of the deposited aluminum was verified by a quartz crystal microbalance and XPS data. The aluminum thickness ranged from about 1 to about 10,000 nm. The RDX crystals were mounted onto a grounded translation stage with double-sided conductive tape to minimize electrical charging.

(21) FIG. 1 shows an N 1s X-ray photoelectron spectrum of RDX crystals, while FIG. 2 shows the N 1s X-ray photoelectron spectrum of the RDX crystals following encapsulation with aluminum of less than 1 nm thickness. Following encapsulation with aluminum, the N 1s spectrum reveals that the nitrogen peak associated with the nitro group is diminished compared to that of the ring structure. This difference is an indication of the preferential reaction of the nitro group of the RDX crystals to the aluminum encapsulation, which leaves the ring structure intact. With increasing thickness of the aluminum encapsulation, the signal associated with the nitro group is diminished further with little change observed in the N 1s intensity of the ring structure.

(22) Experimental results produced aluminum encapsulated RDX crystalline explosive particles of 150-300 microns diameter, each crystal being encapsulated by an aluminum metal thickness of approximately or about 100 nm. Microscopic visualization of the particle-like nature of the encapsulated RDX particles demonstrated that the underlying RDX particles remained intact and were not damaged during encapsulation; the shiny metallic surface of the encapsulated RDX particles was also indicative of a homogenous coating.

(23) Method of Making:

(24) Referring to FIG. 4, in various exemplary embodiments of the invention, a method of making an encapsulated, particulate energetic composition 400 may include placing one of explosive particles of a known size, oxidizer particles of a known size, and a mixture of explosive particles and oxidizer particles of known sizes within a sample cup located in a magnetron sputtering chamber 410, fixing the sample cup at a position and angle relative to a combustible fuel target in the magnetron sputtering chamber 420, and sputtering, to a known encapsulating thickness, a combustible fuel from the combustible fuel target onto one of explosive particles of a known size (distribution), oxidizer particles of a known size (distribution), and a mixture of explosive particles and oxidizer particles of known sizes in the sample cup 430.

(25) Because many varying and different exemplary embodiments may be made with the scope of the inventive concepts taught herein, and because many modifications may be made in the exemplary embodiments detailed herein in accordance with the descriptive requirements of the law, it is to be understood that the detailed descriptions herein are to be interpreted as illustrative and not in a limiting sense.

(26) Finally, any numerical parameters set forth in the specification and attached claims are approximations (for example, by using the term about or approximately) that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of significant digits and by applying ordinary rounding.