Patent Application
20150376079
The present invention relates to energetic material formulations which contain potassium ferrate as an oxidizer for use in pyrotechnic applications. These formulations will eliminate toxic oxidizers, providing environmentally friendly alternative formulations.
Many pyrotechnic compositions contain oxidizers that are not environmentally friendly, such as perchlorates and those containing heavy metals. Replacement of such oxidizers in military munitions has been an area of strong emphasis over the past two decades. Perchlorates, which are used in a wide variety of pyrotechnic formulations, are powerful oxidizers; however, they are also persistent groundwater contaminants and pose health risks by interfering with proper thyroid function. Heavy metal oxidizers are also used in pyrotechnic formulations, especially delays, and pose detrimental environmental and health effects. For example, barium chromate has two major health and environmental impacts due to both its barium and chromium (VI) content. Environmental regulations threaten the use of these types of formulations, so environmentally acceptable alternatives are needed, while retaining performance characteristics.
In one exemplary embodiment of the present disclosure, a pyrotechnic composition comprises a fuel comprised of at least one of magnesium, boron, tungsten, aluminum, and sucrose. The fuel comprises less than half of the pyrotechnic composition. The pyrotechnic composition further comprises an oxidizer comprised of potassium ferrate which comprises more of the pyrotechnic composition than the fuel.
In a further exemplary embodiment of the present disclosure, a pyrotechnic composition comprises a fuel free of perchlorates, chlorates, oxides, peroxides, and heavy metals, an oxidizer comprised of potassium ferrate and free of perchlorates, chlorates, oxides, peroxides, and heavy metals, and a binder.
Another exemplary embodiment of the present disclosures includes a pyrotechnic device comprising a housing including a volume chamber and a pyrotechnic composition received within the volume. The pyrotechnic composition includes a fuel comprised of at least one of magnesium, boron, tungsten, aluminum, and sucrose. The fuel comprises less than half of a weight percentage of the pyrotechnic composition. Additionally, the pyrotechnic composition includes an oxidizer comprised of potassium ferrate and has a greater weight percentage of the pyrotechnic composition than the fuel.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.
DETAILED DESCRIPTION OF THE DRAWINGS
The embodiments of the invention described herein are not intended to be exhaustive or to limit the invention to precise forms disclosed. Rather, the embodiments selected for description have been chosen to enable one skilled in the art to practice the invention.
This invention includes pyrotechnic formulations or charges using potassium ferrate as an oxidizer. Pyrotechnic formulations are comprised of one or more fuels and one or more oxidizers, and may contain a binder and/or other additives. Each formulation has unique thermal and combustion properties, and thus formulations may be optimized to enhance combustion performance depending on the desired application.
Illustratively, with respect to
The pyrotechnic formulations described herein may be used in pyrotechnic apparatus 2 (
Exemplary pyrotechnic formulations covered by this invention are free of, or do not include, chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals (e.g., barium chromate). More particularly, the exemplary pyrotechnic compositions can include the following ingredients: Sucrose (fuel) plus potassium ferrate (oxidizer); Magnesium and sucrose (fuels) plus potassium ferrate (oxidizer); Magnesium (fuel) plus potassium ferrate (oxidizer); Boron (fuel) plus potassium ferrate (oxidizer); Boron (fuel) plus potassium ferrate and potassium periodate (oxidizers); Tungsten (fuel) plus potassium ferrate (oxidizer); Tungsten (fuel) plus potassium ferrate and potassium periodate (oxidizers); Aluminum (fuel) plus potassium ferrate (oxidizer); Magnesium and aluminum or alloy thereof (fuels) plus potassium ferrate (oxidizer). In one embodiment, potassium ferrate is a primary oxidizer and potassium periodate is an auxiliary or secondary oxidizer. As an auxiliary oxidizer, potassium periodate comprises less of the total pyrotechnic composition than potassium ferrate (by weight percentage).
In practice formulations containing these sets of ingredients may include other additives, such as binders, burn rate modifiers, processing aids or other ingredients essential to a desired combustion performance. For example, binders may comprise polymeric-based materials and, in one exemplary embodiment, polytetrafluoroethylene (PTFE) may be used as a binder. Alternatively, the binder materials may be varied to accommodate processing procedures and specific applications for each pyrotechnic formulation.
Example 1: a binary mixture of sucrose plus potassium ferrate may burn more slowly at a low temperature with smoke and minimal flame. This mixture could include an organic dye, and be used as a replacement for sucrose plus potassium chlorate in a smoke formulation.
Example 2: a binary mixture of magnesium plus potassium ferrate may burn more rapidly with an intense orange fireball. By adjusting magnesium particle size and percentages, this mixture could be used as an ignition composition, first-fire, photoflash, illuminant or infrared flare.
Example 3: a binary mixture of boron plus potassium ferrate may burn more rapidly with grey smoke and an orange flash. When polyvinyl chloride is added to this mixture, it may combust more slowly, with a small fireball and dense white smoke. When polytetrafluoroethylene is added instead, it may combust more slowly with no fireball and grey smoke. When potassium periodate is added instead, it may combust more slowly with no fireball and whitish smoke. These formulations could be used as ignition, first-fire or delay compositions, depending on additives and ingredient percentages.
Example 4: a binary mixture of tungsten and potassium ferrate may burn more gently with an orange flame and grey smoke. This formulation could be used as a delay composition.
Example 5: a mixture of boron fuel with a potassium ferrate primary oxidizer and potassium periodate auxiliary, or secondary, oxidizer may combust more slowly. This formulation may be used a delay composition. The mixture of Example 5 comprises less potassium periodate than potassium ferrate in the overall pyrotechnic composition, by percentage.
Example 6: a mixture of tungsten fuel and a potassium ferrate oxidizer may combust more slowly. This formulation may be used as a delay composition.
Example 7: a mixture of tungsten fuel with a potassium ferrate primary oxidizer and potassium periodate auxiliary, or secondary, oxidizer may combust more slowly. This formulation may be used a delay composition. The mixture of Example 7 comprises less potassium periodate than potassium ferrate in the overall pyrotechnic composition, by percentage.
Example 8: a mixture of aluminum fuel and a potassium ferrate oxidizer may burn rapidly and with an intense fireball. This formulation may be used as a photoflash composition.
Example 9: a mixture of magnesium and aluminum fuels, or an alloy thereof, with a potassium ferrate oxidizer may burn rapidly and with an intense fireball. This formulation may be used as an illuminant composition.
Table 1 shows exemplary color base formulations in accordance with embodiments of the invention. In some cases, formulations are fuel-rich and in practice will also contain an organic dye, which is sublimed to form smoke, and a coolant, which acts to reduce the reaction temperature and slow the burn rate. For the Table 1 calculations, no dye was included, an analytical computation used to generate Table 1 results assumed complete combustion for organic dyes. The approach used in creating the Table 1 results yields products including carbon oxides, water and nitrogen oxides, and the reallocation of energy to combust the organic dye that would reduce the predicted reaction temperature significantly. Therefore, only fuels and oxidizers are included in the formulations to compare their predicted reaction temperatures and products.
Exemplary replacement formulation (Mix A) is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, more particularly, can include an oxidizer rich mixture of potassium ferrate and sugar. As shown in Table 1, the oxidizer of replacement formulation Mix A, illustratively potassium ferrate, comprises more than half of the overall composition of the pyrotechnic formulation, by weight percentage. The predicted reaction temperature of 1173 K is much cooler, and a significant fraction of the products are condensed species. Because a fairly cool temperature is predicted, a coolant may not be required for smoke formulations containing potassium ferrate. This could be an added benefit replacement by potassium ferrate. However, the large fraction of condensed species might be unfavorable for smoke cloud formation, as gaseous products may more efficiently transport the volatilized dye into the air.
Some exemplary illuminant compositions are given in Table 2. An exemplary baseline formulation (Mix E) contains fuel and oxidizer used in exemplary illuminating systems. Mix E has a high reaction temperature (>3100 K) and a single condensed product, molten magnesium oxide. Mix C is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, more particularly, contains magnesium and potassium ferrate. As shown in Table 2, the oxidizer of replacement formulation Mix C, illustratively potassium ferrate, comprises more than half of the overall weight percentage of the pyrotechnic formulation. Mix C can be predicted to have a somewhat lower combustion temperature (˜2800 K) and an additional condensed product of iron oxide. Both of these exemplary mixtures (C and E) are fuel-rich. Based on temperatures and condensed species, Mix C may be a feasible illuminant, as magnesium burns brightly.
Exemplary Mix D is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, more particularly, includes an oxidizer-rich with a blend of magnesium and sucrose fuels. Sucrose was added to the mixture with intent of reducing the reaction temperature and, in practice, slowing the reaction rate. A desired shift in stoichiometry should further various effects. As shown in Table 2, the oxidizer of replacement formulation Mix D, illustratively potassium ferrate, comprises more than half of the overall weight percentage of the pyrotechnic formulation. A predicted reaction temperature can be also reduced significantly (1962 K) using an exemplary embodiment. A fraction of condensed products in one embodiment e.g., Mix D, can be close to that of the baseline Mix E, with species of particulate carbon, molten iron and magnesium oxide predicted. Mix D is not as attractive a candidate for an illuminant application.
Thermochemical calculations were also completed for embodiments including magnesium with cesium nitrate, barium nitrate and strontium nitrate, as shown in Table 3. Barium and strontium nitrate can be used with magnesium in colored flares to generate green and red emitters. A replacement with potassium ferrate in some embodiments would not be useful for colored flares, but information regarding their oxidative properties relative to sodium nitrate and potassium ferrate are of interest. Cesium nitrate can be used in a limited number of pyrotechnic formulations. Exemplary Mix F with cesium nitrate was predicted to have a combustion temperature within 5 K of Mix E with sodium nitrate (Table 2), but with a much lower fraction of condensed magnesium oxide. Exemplary Mix G with barium nitrate has been shown to have a slightly lower predicted combustion temperature, and a slightly higher condensed fraction than exemplary Mix F. Exemplary Mix H with strontium nitrate had the highest predicted temperature of the nitrates (3280 K), and a condensed fraction higher than exemplary baseline Mix E, and near that of Mix C with potassium ferrate (See Table 2). Combustion properties predicted for nitrate oxidizers were all similar. Ferrate mixtures (e.g., C and D, Table 2) were demonstrated to have cooler predicted temperatures than all of the nitrate oxidizers. These testing results indicate that the use of ferrate as an oxidizer may require formulation adjustment if high temperature is required.
An igniter composition, boron-potassium nitrate (B-KNO3) was included in experimentation as shown in Table 4. Another exemplary composition (Mix J) has a predicted combustion temperature of 2558 K, and a very small fraction (0.06) of particulate boron nitride as a product.
An additional amount of oxygen was added as a reactant in some experiments conducted to evaluate various embodiments. An exemplary replacement mix with boron and potassium ferrate (Mix I) is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, more particularly, includes a mixture of boron fuel with a potassium ferrate oxidizer and oxygen. The replacement formulation Mix I was shown to have a higher reaction temperature (2763 K) than Mix J and a higher fraction (0.11) of partially oxidized molten iron as its condensed product. These characteristics would make it a good igniter. As shown in Table 4, the oxidizer of replacement formulation Mix I, illustratively potassium ferrate, comprises more than half of the overall weight percentage of the pyrotechnic formulation.
As potassium perchlorate is one of the oxidizers that under consideration as a being replaced with potassium ferrate, its behavior with boron was also investigated. Exemplary Mix K is a stoichiometric mixture with a predicted combustion temperature of 3070 K and no condensed products. Exemplary Mix I has a combustion temperature 300 degrees lower than Mix K and small fraction of condensed products. In general, boron with potassium ferrate was shown to burn cooler than boron with potassium perchlorate, but hotter than boron with potassium nitrate.
15a
A common boron delay formulation is listed in Table 5. Exemplary Mix M included a slightly fuel rich mixture of boron and barium chromate. Mix M has a predicted reaction temperature near 2100 K, and a high condensed fraction (0.71), comprised mainly of molten boric oxide and solid barium oxide and chromium. Two ferrate-containing compositions were simulated. Mix I (Table 4) is an oxidizer-rich mixture of boron and potassium ferrate, with a predicted reaction temperature of 2756 K and a condensed fraction of only 0.11. This is significantly hotter and has a much higher fraction of gaseous products than either baseline. For this reason Mix I may not function well as a delay.
Mix L is fuel-rich and contains PVC. Illustratively, the replacement formulation Mix L is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, more particularly, includes a boron fuel, a potassium ferrate oxidizer, PVC, and oxygen. Oxygen was included in this simulation to obtain convergence. In both cases where potassium ferrate was substituted for barium chromate, more gaseous products are predicted than for the baseline. An addition of PVC did cool the temperature to near that of a baseline but still yielded a low percentage of condensed products. As shown in Table 5, the oxidizer of replacement formulation Mix L, illustratively potassium ferrate, comprises more than half of the overall weight percentage of the pyrotechnic formulation.
10a
Mix O can include a common delay formulation containing tungsten fuel, barium chromate and potassium perchlorate oxidizers, and VAAR (vinyl acetate alkyl resin) binder, as shown in Table 6. This is fuel-rich and has a predicted combustion temperature of 1602 K and a condensed product fraction of 0.88. Tungsten with potassium ferrate (Mix N) is a stoichiometric mixture with a predicted combustion temperature of 1375 K and all condensed products. Oxygen (16%) had to be included in the simulation for convergence. The replacement formulation Mix N is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, as shown in Table 6, the oxidizer of replacement formulation Mix N, illustratively potassium ferrate, comprises more than half of the overall weight percentage of the pyrotechnic formulation. Mix N may be a feasible replacement for a delay application.
Both magnesium and aluminum when combined with potassium perchlorate react with a very energetic flash and report. Exemplary Mix Q in Table 7 includes a slightly fuel-rich flash composition. Mix Q contains more fuel than a typical oxidizer-rich flash composition would. Its predicted reaction temperature is 3802 K, the highest predicted in this study. Its only condensed product is alumina. Mix P is free of chlorate materials, perchlorate materials, oxide materials, peroxide materials, and heavy metals and, more particularly, is a stoichiometric mix of aluminum and potassium ferrate. As shown in Table 7, the oxidizer of replacement formulation Mix P, illustratively potassium ferrate, comprises more than half of the overall weight percentage of the pyrotechnic formulation. Its predicted reaction temperature is 1000 K lower, with nearly 60% condensed products. Mix C (Table 2), which contains magnesium and potassium ferrate, has a similar predicted temperature and condensed products. The predicted temperature is also close to the predicted temperature for boron and ferrate (Mix I, Table 4). In general, when perchlorate is replaced with ferrate, temperature is reduced and more condensed species are formed. This reduction in temperature may not be favorable for use as a flash composition.
Some advantages of exemplary embodiments of the invention include the minimal environmental and health impact. Potassium ferrate will replace hazardous ingredients such as perchlorates, chlorates, oxides, peroxides, and heavy metals, such as barium, chromium, and lead, in current pyrotechnic formulations. Potassium ferrate, when mixed with fuel, will combust into final products which include iron oxide (rust), which has no known hazards. Potassium ferrate is currently used as an oxidizer for treatment of wastewater. As the using activities spends more funds on mitigating the use and cleanup of hazardous materials, the use of environmentally friendly pyrotechnic formulations will be a major investment by such activities and private industries. The activities must ensure that the use of potassium ferrate by activities is protected and that private entities should not develop and charge activities for the use of environmentally-friendly pyrotechnic formulations with potassium ferrate.
Theoretical modeling predictions indicated that potassium ferrate may be a feasible alternative oxidizer in certain embodiments. Flame temperatures and combustion products were comparable to baseline formulations in several, but not all cases. This material may be a viable oxidizer for smokes, illuminants, igniters, and tungsten-based delays. It is noted that in all cases where potassium ferrate was directly substituted for potassium perchlorate, the temperature predicted was significantly lower (300K-1000K). For this reason potassium ferrate may not be a suitable drop-in replacement for potassium perchlorate in all embodiments thus cannot be considered an obvious design choice.
Potassium ferrate is environmentally friendly because it contains no heavy metals, chlorides, or other halogen impurities. It is shelf-stable and its decomposition by-product is rust. In addition, potassium ferrate may be able to generate a secondary catalytic effect (e.g. Fe2O3) to further oxidize the combustion products to much more environmentally-friendly chemical species.
Based on these initial data, it is highly probable that formulations incorporating potassium ferrate will results in reactive compositions that will ignite and sustain combustion. Because a single set of percentages was used to perform calculations, formulation adjustments will be needed to obtain required temperature and reaction rates in practice. A set of formulations has been identified for further study and characterization, including combustion testing in various embodiments.
As previously discussed, any of these pyrotechnic compositions may be included in an embodiment of pyrotechnic apparatus 2. For example, the pyrotechnic composition may be received within volume chamber 6 of housing 4. Cap 8 may be sealed or otherwise coupled to housing 4 to retain the pyrotechnic composition therein. Additionally, trigger mechanism 10 may be operably coupled to the pyrotechnic composition for detonating the pyrotechnic composition and achieving a desired effect (e.g., delayed detonation, ignition of additional pyrotechnic compositions, first-fire, photoflash, illumination, infrared flare, smoke).
Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the spirit and scope of the invention as described and defined in the following claims.
The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/950,068, entitled FERRATE BASED PYROTECHNIC FORMULATIONS and filed on Mar. 8, 2014 (Attorney Docket No. NC 102,260), and U.S. Provisional Patent Application Ser. No. 61/977,283, entitled FERRATE BASED PYROTECHNIC FORMULATIONS and filed on Apr. 9, 2014 (Attorney Docket No. NC 102,260A), the complete disclosures of which are expressly incorporated by reference herein.
The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used and licensed by or for the United States Government for any governmental purpose without payment of any royalties thereon. This invention (NC 103,100) is assigned to the United Stated Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Technology Transfer Office, Naval Surface Warfare Center Crane, email: Cran_CTO@navy.mil.
| Number | Date | Country | |
|---|---|---|---|
| 61977283 | Apr 2014 | US | |
| 61950068 | Mar 2014 | US |
