Explosive and thermic compositions or charges – Metal or alloy or metalloid – each in particulate form – with...
Reexamination Certificate
2003-02-13
2003-12-23
Miller, Edward A. (Department: 3641)
Explosive and thermic compositions or charges
Metal or alloy or metalloid, each in particulate form, with...
C149S006000
Reexamination Certificate
active
06666936
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to coated metal particles and more particularly to particles having a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer covalently attached to the buffer layer.
BACKGROUND OF THE INVENTION
Explosives are energetic materials that typically include an oxidant and a reductant that react rapidly with each other to produce product gases (e.g. CO
2
, H
2
O, and others) and energy in the form of heat and shock. Explosives include materials such as TNT, TATB, RDX, nitroglycerine, and the like, which produce energy at a very fast and uncontrolled rate. For applications that require a more controlled rate of energy production, “metastable intersitital composite” (MIC) materials have been developed.
MIC materials have been described, for example, in U.S. Pat. No. 5,266,132 to W. C. Danen et al. entitled “Energetic Composites,” and in U.S. Pat. No. 5,606,146 to W. C. Danen et al. entitled “Energetic Composites and Method of Providing Chemical Energy,” both hereby incorporated by reference. The MIC materials described in the '132 and '146 patents are layered materials that include alternating layers of oxidant and reductant. The oxidant layers are physically separated from the reductant layers by buffer layers. When the buffer layers are disrupted, the oxidant and reductant layers come into contact and react to produce chemical energy. The amount of energy produced and the rate of energy production depend on, among other things, the chemical composition of the oxidant and reductant layers and the number and thickness of these layers.
MIC materials in the form of powders are also known (see U.S. Pat. No. 5,717,159 to G. Dixon et al. entitled “Lead-Free Percussion Primer Mixes Based on Metastable Interstitial Composite (MIC) Technology,” hereby incorporated by reference). The MIC powders of the '159 patent are a blend of oxidant powder and reductant powder. The powders are used as percussion primers. The reductant powder is aluminum powder made up of aluminum particles having a thin oxide coating. One percussion primer composition is a mixture of about 45 wt % of reductant aluminum powder and about 55 wt % of oxidant molybdenum trioxide powder. Another primer composition is a mixture of about 50 wt % aluminum powder and about 50 wt % polytetrafluoroethylene. The particle sizes are less than 0.1 micron, and preferably from about 200-500 Angstroms.
A problem common to these known MIC materials is their susceptibility to degradation upon aging, which typically involves the slow oxidation of reactive metal reductant to the corresponding unreactive metal oxide. Using a MIC powder composition that includes aluminum powder and molybdenum trioxide as a example, as more of the aluminum metal degrades and is converted to unreactive aluminum oxide, less aluminum is available for reaction with molybdenum trioxide. Thus, aging through oxidative degradation of reductant metal powder reduces the shelf life and performance of MIC materials. To ensure that the performance of these types of materials is maintained during storage and under conditions that promote degradation, there remains a need for MIC materials and MIC components that are more resistant to degradation.
Therefore, an object of the present invention is to provide MIC materials that are more resistant to degradation.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes powder particles having a central metal core, a buffer layer surrounding the central metal core, and a fluoroalkylsilane layer surrounding and covalently bonded to the buffer layer.
The invention also includes energetic powder. The energetic powder is a blend of reductant powder and oxidant powder. The reductant powder includes particles having a central metal core, a buffer layer surrounding the central metal core, and a fluoroalkylsilane layer surrounding and covalently bonded to the buffer layer. The oxidant powder includes oxidant powder particles that chemically react with the reductant powder particles to release chemical energy.
The invention also includes a method of releasing energy. The method involves providing energetic powder particles having a central metal core, a buffer layer surrounding the central metal core, and a fluoroalkylsilane layer that surrounds and is covalently bonded to the buffer layer. When the buffer layer is disrupted, the metal core contacts and chemically reacts with the fluoroalkylsilane layer to release chemical energy.
The invention also includes a method of releasing chemical energy. The method involves providing an energetic powder that includes an oxidant powder blended with a reductant powder. The reductant powder includes particles having a central metal core, a buffer layer that surrounds the central metal core, and a fluoroalkylsilane layer that surrounds and is covalently bonded to the buffer layer. Disrupting the buffer layer brings the metal core and oxidant powder into contact so that they can chemically react and release energy.
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Atsushi Hozumi et al., “Fluoroalkylsilane Monolayers Formed by Chemical Vapor Surface Modification on Hydroxylated Oxide Surfaces,” Langmuir, 1999, No. 22, vol. 15, pp. 7600-7604.
Stephen R. Wasserman et al., “Structure and Reactivity of Alkylsiloxane Monolayers Formed by Reaction of Alkyltrichlorosilanes on Silicon Substrates,” Langmuir, 1989, No. 4, vol. 5, pp. 1074-1087.
C. E. Aumann et al., “Oxidation Behavior of Aluminum Nanopowders,” J. Vac. Sci. Technol. B., vol. 13(3), May/Jun. 1995.
C. G. Granqvist et al., “Ultrafine Metal Particles,” Journal of Applied Physics, vol. 47, No. 5, pp. 2200-2219, May 1976.
Danen Wayne C.
Jorgensen Betty S.
Borkowsky Samuel L.
Miller Edward A.
The Regents of the University of California
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