Patent Application
20050189050
The present disclosure relates to energetic material compositions. More specifically, the present disclosure relates to an energetic material composition based on oxide of phosphorus and its use in munitions, for example to neutralize a target agent and/or to reduce structural integrity of a civil engineering structure.
In the discussion of the state of the art that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention
A typical warhead configuration includes a hard casing which carries a payload material. The hard casing often includes a substantially elongated cylindrical body with an ogive shaped nose section. Such warheads can be deployed by cruise or ballistic missiles or by release from an aircraft, but are not limited to such deployment. Examples of current conventional warheads include the BLU-109, BLU-113, BLU-116, the Mk-82, Mk-83 and Mk-84 warheads. In some configurations, these warheads are a hard target penetrating warhead, designed to penetrate a hardened structural defense and deliver a main explosive payload to the interior of the structure.
Dissemination of weapons of mass destruction based on chemical or biological agents has compounded the difficulty in targeting and successfully destroying targets, including hardened targets, which contain such chemical or biological agents.
Conventional prompt agent defeat (PAD) and thermobaric (TBX) weapons are filled with white phosphorus and high explosive. The high explosive disperses the white phosphorus when the high explosive detonates. Dispersed white phosphorus burns when exposed to air and releases heat. The heat generated by white phosphorus can be used in a PAD weapon as a neutralizing agent, such as for neutralizing a chemical weapon, and/or can be used in a TBX weapon to create a thermobaric effect, in which a differential pressure induces or enhances the explosive effect of the weapon. Further, oxides of phosphorus resulting from the dispersion event and the burning event can combine with water to form phosphoric acid to therebv generate a residual agent neutralizing effect.
Because white phosphorus is pyrophoric, white phosphorus requires extensive safeguards for safe handling and storage. Typically, to prevent auto-ignition or to provide stable storage, white phosphorus is excluded from air, which complicates handling and storage procedures.
Representative devices for delivery of active biological and/or chemical agents are disclosed in U.S. Pat. No. 3,831,520 to Bowen et al., U.S. Pat. No. 3,661,083 to Weimholt and U.S. Pat. No. 3,596,602 to Gey et al. Generally, these devices do not disclose delivery of neutralizing agents. An example of an energy dense explosive (EDE), wherein particles of a reducing metal and a metal oxide are dispersed throughout a conventional high explosive, is disclosed in U.S. Pat. No. 5,505,799 to Jones. An example of a heat generating material is disclosed in U.S. Pat. No. 5,505,799 to Makowiecki.
There is a need for a substitute material for white phosphorus that is more stable, yet provides at least some of the performance of conventional white phosphorus, particularly in a weapon application.
An exemplary energetic material composition comprises a reducing material and an oxide of phosphorus.
An exemplary method of neutralizing a targeted species comprises reacting a composition including a reducing material and an oxide of phosphorus to generate heat and to produce elemental phosphorus, and at least one of exposing the targeted species to the generated heat and exposing the targeted species to phosphoric acid formed from a product of reacting the reducing material and the oxide of phosphorus.
An exemplary method of reducing a structural integrity of a civil engineering structure comprises reacting a composition including a reducing material and an oxide of phosphorus to create a differential pressure, and exposing the civil engineering structure to the differential pressure.
An exemplary munition comprises a warhead having a cavity, and a composition including a reducing material and an oxide of phosphorus, the composition arranged in the cavity.
The following detailed description of preferred embodiments can be read in connection with the accompanying drawings in which like numerals designate like elements and in which:
The constituents of the energetic material composition can, upon initiation of a reaction, release energy and elemental phosphorus as a reaction product. The energetic material composition generally reacts as follows:
where M is a reducing material, PxOy is an oxide of phosphorus, MnOp is an oxide of the reducing material, P is elemental phosphorus, Δheat is a change in heat, and coefficients a, b, c, and d balance the reaction either stoichiometrically or non-stochiometrically. This reaction is autocatalytic once initiated by, for example, a fuse. Other suitable initiation mechanisms, δ, can also be used.
In one exemplary embodiment, the reducing material is a reducing metal. For example, the reducing metal can be selected from the group consisting of Li, Na, K, Be, Mg, Ca, B, Al, Ga, Ti, Zr, Zn, Cd, and alloys or mixtures thereof. In a preferred embodiment, the reducing material is aluminum. In another preferred embodiment, the reducing material is a hydride of the reducing metal.
In a further exemplary embodiment, the reducing material has a sufficiently high negative enthalpy in reaction with the oxide of phosphorus to produce a sufficient heat to neutralize a targeted agent. For example, a targeted agent can be a biological or chemical species and the heat derived in an exothermic reaction of reducing material and oxide of phosphorus is sufficient to neutralize the species. The capability of the material composition to produce a sufficient heat is preferred where the targeted agent is, for example, a biological or chemical agent capable of use in a weapon, such as a nerve agent or an infectious agent.
An example of a sufficiently high negative enthalpy, e.g., an exothermic enthalpy, in reaction with an oxide of phosphorus, e.g., P4O10, includes exothermic enthalpies in the range of approximately (e.g., ±10%) 400 cal per mole of oxide of phosphorous to 1300 cal per mole of oxide of phosphorous. Preferably, the oxide of phosphorous is P4O10 and the reducing material is aluminum or aluminum-based, e.g., an alloy or mixture of including aluminum.
Typically, sufficient heat in the context of neutralizing a targeted agent is greater than 100° C. Preferably, sufficient heat is greater than 300° C. and more preferably greater than 500° C. The sufficient heat is at temperature for at least a sustained period of time, such as, for example, one to three seconds. The time-temperature relationship varies for specific targeted agents, but is generally an inverse relationship, e.g., a higher temperature can be sustained for a shorter time and a lower temperature can be sustained for a longer time to obtain comparable neutralizing effect. The time-temperature relationship can be readily determined for a particular targeted agent.
In one exemplary embodiment, the oxide of phosphorus includes a stoichiometric oxide of phosphorous. For example, the stoichiometric oxide of phosphorous can be phosphorus pentoxide, P4O10. However, examples of oxides of phosphorus that may be used in the energetic material composition can also include non-stoichiometric oxides of phosphorous. These non-stoichiometric oxides of phosphorous can be used with reducing materials of suitable exothermic reaction enthalpies as described and disclosed herein.
The energetic material composition may be in the munition in any suitable form. For example, the exemplary embodiment of
In one exemplary embodiment, powders of individual constituents of the energetic composition were milled mechanically, e.g. in a ball mill, or manually, e.g. with mortar and pestle, to an average diameter of less than 10 microns. The powders of the individual constituents were then jointly milled, mechanically or manually, to produce the final mixture. This final mixture was then available for reaction, for example, in a reaction initiated by a fuse, such as a nichrome bridgewire initiator.
Other forms of the energetic material composition may include substantially segregating the reducing material and the oxide of phosphorus. For example,
Still further, the layers may have a transition zone between adjacent layers. For example, an adjacent first layer and second layer can have a gradient where the composition of the first layer decreases and the composition of the second layer increases as position within the layers changes from the first layer to the second layer. In other words, there is a compositional, transitional area between the species of the layers. In an additional example, a powder of a first species of the energetic composition may be poured into a cavity and optionally settled or leveled to form a first layer. A powder of a second species of the energetic composition may be poured into the cavity over a portion or over the whole of the first layer and optionally settled or leveled to form a second layer. This procedure may be repeated for as many species, e.g., two, three, four, or more, and as many layers, e.g., two, three, four, or more, as desired. The first layer and the second layer are not strictly separated, but rather are intermingled in the thickness of the transition zone where the powder of a second species was poured over the powder of the first species.
Thickness of each layer, whether a solid layer, powder layer or other form of layer, is generally such that a substantial amount, e.g., greater than 75%, preferably greater than 90%, of the constituents of the energetic composition participate in the reaction during any reaction. In other words, there is less than 25% unreacted material, preferably less than 10% unreacted material. The thickness of the layers is at least partially dependent on the length scales of the reaction kinetics. In one preferred example, the powder of each of the constituents is about (±10%) 500 microns in average diameter and the layer thickness of a layer of any one species is about (±10%) three times the average diameter, e.g. about 1500 microns for this example. Other sizes of powders and thicknesses of layers are contemplated, as disclosed herein.
In exemplary embodiments, a dispersant aid is included to assist in dispersing the elemental phosphorus reaction product. For example, a high explosive can be included in the munition, which, upon detonation, disperses the elemental phosphorus.
In preferred embodiments, the dispersing aid is integrated into the energetic material composition. For example, the dispersing aid can include a metal hydride, such as a metal hydride of a reducing metal disclosed herein. Initiation of the reaction of the energetic material composition, e.g., the reaction between the reducing metal hydride and the oxide of phosphorus, results in, in addition to the above disclosed heat and elemental phosphorus, an evolved gaseous product, such as hydrogen gas. The evolved gaseous product assists in dispersing the elemental phosphorus. In such preferred embodiments, a separate and dedicated dispersing aid, such as a high explosive, is preferably not utilized, although a high explosive based dispersing aid may optionally be included, for example, for additional dispersing power.
In general, exemplary embodiments of the energetic material composition can be used in a munition, such as in PAD or TBX weapons. For example, the heat generated by the elemental phosphorus can be used as a neutralizing agent, such as for a chemical species or a biological species, and/or can be used to create a thermobaric effect, in which a differential pressure induces or enhances the explosive effect of the weapon. Further, elemental phosphorus resulting from the dispersion event and the burning event can combine with water to form phosphoric acid. The phosphoric acid can generate a residual agent neutralizing effect.
An exemplary method of neutralizing a targeted species is shown in
In exemplary embodiments, overpressure can be generated through the production of hot gaseous reaction products. The overpressure can be used to damage structures, e.g., reducing structural integrity by collapsing walls, breaking windows, and/or breaking doors. Either the whole structure or a portion of the structure can be damaged.
An exemplary method of reducing a structural integrity of a civil engineering structure is shown in
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims.
This application claims the benefit of U.S. Provisional Patent Application No. 60/536,231, filed on Jan. 14, 2004, entitled “PHOSPHORUS OXIDE BASED ENERGETIC MATERIAL,” the entire content of which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60536231 | Jan 2004 | US |
