Patent Application
20110239890
The present invention pertains generally to materials, systems and methods for creating metal foams. More particularly, the present invention pertains to formulations wherein a foaming agent is combined with thermite to create a metal foam in response to an ignition of thermite. The present invention is particularly, but not exclusively, useful as a material, system and method for enveloping and neutralizing chemical and biological (C/B) warfare agent weapons and facilities.
It is well known that many chemical and biological (C/B) agents are, by design, toxic or very hazardous materials. When released, they can be dispersed over a wide area where they pose serious threats to life and property. To prevent such potential situations, it is essential that enemy access to C/B agent storage and production facilities be denied while also ensuring the agents be somehow neutralized or destroyed. Often this requires immediate action under circumstances (e.g. combat) that are not conducive to a more methodical operation. Conventional explosive munitions have been considered as an immediate response. Explosive munitions, however, can exacerbate the situation by contributing to an unwanted dispersal of the C/B agents.
An effective way of denying access to C/B agents is to envelop them in a manner that will prevent their further dispersal. Specifically, such a restrictive confinement requires enveloping the C/B materials within a rigid barrier. Preferably, as alluded to above, this process can be accomplished quickly and efficiently under hostile conditions, without dispersing the C/B agents.
Any of several types of well known metal foams may be suitable for the purpose of enveloping C/B materials. In particular, foams generally known as closed cell foams are preferable in order to minimize the chance of agent release. The creation of such foams, however, typically requires elevated temperatures. In the context of a system for creating a metal foam that can be used to confine and neutralize C/B materials (i.e. where the system is an Agent Defeat Weapon), the metal foam is preferably created by a heat-activated-chemical (HAC) method that will generate the required elevated temperatures. Thermite provides such an HAC method.
In the most common form of thermite, aluminum-iron (III) oxide, aluminum (Al) reduces the iron oxide to produce a large exothermic heat of reaction and molten iron. The reaction is:
Fe2O3+2Al2Fe+Al2O3+Heat
Operational temperatures in excess of 2000° C. have been developed with the above stated reaction.
In light of the above, it is an object of the present invention to provide an HAC material, system and method for creating a metal foam that envelops and neutralizes a target thought to include C/B agents. The target may include warehoused or stored munitions, bulk materials, and/or manufacturing facilities and supplies related to C/B agents. Another object of the present invention is to provide a system and method for creating a metal foam that can be used to render C/B materials unusable by virtue of the solidified metal foam adhering to surfaces of the C/B material containers or facilities. Still another object of the present invention is to provide a material, system and method for creating a metal foam in response to the ignition of a thermite powder formulation. Yet another object of the present invention is to provide a material, system and method for creating a metal foam that is easy to use, simple to manufacture, and cost effective.
In accordance with the present invention, a material, system and method for creating a metal foam are provided. Specific purposes for this metal foam are to envelop and neutralize C/B targets or to disable facilities and munitions. In detail, a formulation for creating the metal foam includes thermite, and a foaming agent that is admixed with the thermite. Together the resultant formulation creates a powdered thermite/metal matrix. In addition to the molten iron inherent to the reacting thermite, secondary melt-forming metals may be included in the formulation to adjust the necessary foaming conditions, such as temperature. The formulation may also include a thickening agent that is blended into the powder matrix (formulation) to provide the most favorable foaming properties as the thermite reacts. Additionally, the powder matrix (formulation) can include a heat sink agent that is dispersed throughout the powder matrix to moderate the temperature of the matrix during the thermite reaction. The powder matrix may also include a binder that is combined with the matrix for holding the constituents together.
As envisioned for the present invention, the thermite preferably comprises an aluminum (Al) powder fuel component having particles with diameters in a range of about three to one hundred and thirty microns (3-130 microns). The thermite will also include an iron oxide oxidant powder having particles less than about one micron (<1 micron) in diameter. In the preferred embodiment, the oxidant may be either red Fe2O3 or black Fe3O4. In the case of red Fe2O3, the aluminum (Al) and iron oxide will typically be mixed together in a weight ratio of approximately 8:3. For black Fe3O4, a weight ratio of approximately 3:1 will typically be used.
Alternative formulations for the thermite are also envisioned for the present invention. For example, the formulation may contain excess Al over that described in the preceding paragraph, resulting in a mixture of molten iron and aluminum that may be more easily foamed. In other alternate embodiments, the Al fuel component of the thermite can be replaced with Mg, Ca, Ti, Zn, Si or B. Further, along with the replacements for Al, the oxidant for alternate embodiments of the thermite can be selected from a group consisting of B2O3, SiO2, Cr2O3, MnO2 and CuO.
For the present invention, the foaming agent (a.k.a. blowing agent) may be selected from a group consisting of FeO+C, SrCO3, VO2+C, Cr2O3+C, MnO+C and TiH2. In particular, the content of the foaming agent in the formulation will be, for example, less than about 2.5 wt % of the metal foam, and the foaming agent will be made of particles having diameters in the range of one to two microns (1-2 microns). The thickening agent may be selected from a group consisting of SiC, Al2O3 and MgO. Typically, the thickening agent will be about 10-30 wt % of the metal foam and will be made up, for example, of particles of five to twenty microns (5-20 microns) in diameter. The heat sink agent may be TiC and will, for example, be less than about 10 wt % of the metal foam. In the powder formulation, the heat sink agent will have particle sizes between one and three microns (1-3 microns). As mentioned above, the powder formulation may include a binder. If so, the binder will typically be selected from a group consisting of KBr, NaBr, CaBr2 and S. The binder will normally be between about 5-8 wt % of the metal foam and, in the powder formulation, will have particle sizes of about 5 microns diameter.
In the preceding concept, the metal foam is formed from the molten iron phase that results from the thermite reaction. In an alternative binary munition concept, the thermite constituents and metal foam constituents are not mixed together but, instead, packaged side-by-side. Heat from the thermite reaction is transferred to the foam forming mixture, allowing formation of foam from a molten phase other than that associated with the thermite reaction.
When used in a system, the powder formulation is placed in a canister and an igniter is provided to initiate a reaction in the formulation. This reaction will then create the metal foam. In use, the canister holding the formulation can be deployed to the C/B target by any of several means. Examples of possible delivery means include: manned or unmanned aircraft, rocket or artillery delivery systems, and hand delivery. The delivery means may include apparatus for dispersing the foam or foam forming constituents or canisters. Regardless of how it may be delivered, when ignited at or approaching the target, the formulation turns into a molten metal foam that surrounds and envelops the target. In this process, as the metal foam is enveloping the target, it freezes to envelop and neutralize the target.
The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
Referring initially to
In accordance with the present invention, the essential ingredients 12 of the formulation 10 are thermite 16 and a foaming agent 18. Further, the thermite portion of the formulation 10 will include both a metal component and an oxidant. Preferably, the component is a metal such as Al, and the oxidant is an iron oxide that can be either Fe2O3 or Fe3O4. There are, however, possible alternatives for the metal component Al. Also, there are possible alternatives for the oxidant (Fe2O3 or Fe3O4). For example, Al can be selectively replaced by Mg, Ca, Ti, Zn, Si or B, and the oxidant can be selectively replaced by B2O3, SiO2, Cr2O3, MnO2 or CuO. Additional details about these constituents of the thermite 16, as well as details for other possible constituents of the formulation 10, are set forth in the Table provided in
Insofar as possible additives 14 for the formulation 10 are concerned, they may include a thickening agent 20, a heat sink agent 22, and a binder 24. Specifically, in order, the thickening agent 20 can be provided for the purpose of increasing the viscosity of the molten metal that results during a thermal reaction of the formulation 10. Specifically, if used, the thickening agent 20 will help the molten metal maintain suitable characteristics as it is being transformed into a metallic foam 26 (see
Still referring to
In use, a canister 28 that has been filled with the formulation 10 is somehow positioned in near proximity to a target 32 as shown in
Note that in some cases, it may be advantageous to initiate the foaming reaction while the device is still en route to the target to allow effective dispersal and envelopment from above. Furthermore, the delivery device may advantageously contain multiple submunitions and dispersal methods to facilitate more effective dispersal of the foam forming charges.
In an alternative binary munition concept, the thermite constituents and metal foam constituents are not mixed together but arranged side-by-side. Heat from the ignited thermite reaction is transferred to the foaming composition, allowing formation of foam from a molten phase other than that associated with the thermite reaction. This embodiment can enable the use of lower-temperature molten metals that are easier to foam and less prone to penetrate the agent container, hence reducing the chance of unintended agent release.
While the particular Thermite-Metal Foam as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.
