Composite reactive materials with independently controllable ignition and combustion properties

Abstract

The present invention is directed to composite particles that react with a small and adjustable input energy. The ignition threshold depends primarily upon reactant spacing and chemistry, not overall particle size. Combustion properties, such as burn duration and temperature, are controlled by adjusting particle size or reactant composition. The best performance is achieved by selecting reactants with strong intermetallic formation reaction and that combust in different phases (condensed vs gaseous). These particles are fabricated by various methods, including physical vapor deposition, or ball milling. The concept of purposefully decoupling ignition and combustion properties by fabricating particles where ignition is determined by reactant spacing and/or composition and combustion is determined by adjusting particle size and/or composition is described. Combinations of specific reactants, such as Al, Zr, Ti, Mo, Mg, B, Li, etc. exhibit dual-phase combustion, and/or enhance combustion through prevention of terminating species. Ternary additions are used to form gaseous species.

1 . A composite particle comprising: two or more elemental or metallic alloy reactants; and wherein spacing and average composition of the two or more elemental or metallic alloy reactants are controlled so as to enable and tune an exothermic formation reaction that leads to an extensive combustion reaction of a product where the combustion reaction is controlled through use of chemistry and/or particle size. 
     
     
         2 . The composite particles of  claim 1  wherein an average reactant spacing is between 100 nm and 10 μm, so as to tune (e.g. lower) threshold for igniting the exothermic formation reaction. 
     
     
         3 . The composite particle of  claim 1  wherein a chemistry for the exothermic formation reaction comprises a primary reactant taking a form of one chosen from a group consisting of Al or an Al alloy and a secondary reactant taking a form of one chosen from a group consisting of B, Co, Ti, Zr, Hf, Nb, or V and an average composition ranges from 10Al:X to Al:10X wherein X is the secondary reactant. 
     
     
         4 . The composite particle of  claim 1  wherein a chemistry for the exothermic formation reaction comprises a primary reactant taking a form of one chosen from a group consisting of B or a B alloy and a secondary reactant taking the form of one chosen from a group consisting of Hf, Mg, Mo, Nb, Ta, Ti, V, or Zr and an average composition ranges from 10B:X to B:10X wherein X is the secondary reactant. 
     
     
         5 . The composite particle of  claim 1  wherein a chemistry for the exothermic formation reaction comprises a primary reactant taking a form of one chosen from a group consisting of a C or a C alloy and a secondary reactant taking a form of one chosen from a group consisting of Hf, Nb, Si, Ta, Ti, V, or Zr and an average composition ranges from 10C:X to C:10X wherein X is the secondary reactant. 
     
     
         6 . The composite particle of  claim 1  wherein a chemistry for the exothermic formation reaction comprises a primary reactant taking a form of one chosen from a group consisting of Si or a Si alloy and secondary reactant taking a form of one chosen from a group consisting of Mo, Nb, V, Zr, Ti, Hf, or Ta and an average composition ranges from 10Si:X to Si:10X wherein X is the secondary reactant. 
     
     
         7 . The composite particles of  claim 1  wherein the composite particle contains at least one component that undergoes a vapor phase combustion such as one chosen from a group consisting of Al, B, Mg, Ca, Li, K, or Na for enhanced combustion. 
     
     
         8 . The composite particle of  claim 1  wherein the composite particle has a ternary addition that is one chosen from a group consisting of Mg, Ca, Li, K, or Na for enhanced ignition, wherein an atomic percentage of an alloying element is varied between 0 and 25% within a system of primary reactants. 
     
     
         9 . The composite particle of  claim 1  wherein the composite particle has a ternary addition that could be one of, but is not limited to one chosen from a group consisting of Mg, Ca, Li, K, or Na for enhanced combustion, wherein an atomic percentage of an alloying element is varied between 0 and 25% within a system of primary reactants. 
     
     
         10 . The composite particle of  claim 1  wherein the composite particle has a binary chemistry and one or more ternary additions that are chosen from a group consisting of Mg, Ca, Li, K, or Na for modified reaction pathways that minimize formation of unwanted low energy byproducts during combustion. 
     
     
         11 . The composite particle of  claim 1  further comprising composite particles whose average diameter is between 100 nm and 500 μm so as to tune a duration of the combustion reaction independently from ignition thresholds. 
     
     
         12 . A composite particle comprising: two or more elemental or metallic alloy reactants; wherein a spacing of the two or more elemental or metallic alloy reactants is controlled so as to tune and enable an exothermic formation reaction; and, wherein a chemistry of the two or more elemental or metallic alloy reactants is chosen so as to lead to a combustion reaction that is dual phase (condensed and vapor). 
     
     
         13 . The composite particle of  claim 12  further comprising the composite particle in which an average reactant spacing is between 100 nm and 10 μm, so as to tune a threshold for igniting the exothermic formation reaction independently from combustion behavior. 
     
     
         14 . The composite particle of  claim 12  further comprising the composite particle in which an average particle diameter is between 100 nm and 500 μm, so as to tune a duration of the combustion reaction independently from ignition thresholds. 
     
     
         15 . The composite particles of  claim 12  wherein a chemistry for the exothermic formation reaction comprises a primary vapor phase reactant taking a form of Al or an Al alloy and a secondary solid phase reactant taking a form of one chosen from a group consisting of Ti, Zr, Ta, Mb, V, or Hf and an average composition ranges from 10Al:X to Al:10X where X is the secondary reactant. 
     
     
         16 . The composite particle of  claim 12  wherein a chemistry for the exothermic formation reaction comprises a primary vapor phase reactant taking a form of B or a B alloy and a secondary solid phase reactant taking a form of one chosen from a group consisting of Ti, Zr, Ta, Mb, V, or Hf and an average composition ranges from 10B:X to B:10X where X is the secondary reactant. 
     
     
         17 . The composite particle of  claim 12  wherein the composite particle contains one component that enhances vapor phase combustion and is one chosen from a group consisting of Al, B, Mg, Ca, Li, K, or Na. 
     
     
         18 . The composite particle of  claim 12  having a ternary addition that is one chosen from a group consisting of Mg, Ca, Li, K, or Na for modified reaction pathways that minimize formation of unwanted low energy byproducts during combustion. 
     
     
         19 . The composite particle of  claim 12  wherein the composite particle has a ternary addition that is one chosen from a group consisting of Mg, Ca, Li, K, or Na for enhanced ignition, wherein an atomic percentage of an alloying element is varied between 0 and 25% within a system of primary reactants. 
     
     
         20 . The composite particle of  claim 12  having a ternary addition that is one chosen from a group consisting of Mg, Ca, Li, K, or Na for enhanced vapor phase combustion, wherein an atomic percentage of an alloying element is varied between 0 and 25% within a system of primary reactants. 
     
     
         21 . The composite particles of  claim 12  having a ternary addition that could be one of, but is not limited to Mg, Ca, Li, K, or Na for enhanced condensed phase combustion, wherein an atomic percentage of an alloying element is varied between 0 and 25% within a system of primary reactants. 
     
     
         22 . A composite particle comprising: two or more reactants; wherein one of the two or more reactants is alloyed with a more volatile element to enhance combustion, and an atomic percentage of an alloying element is varied to control combustion properties. 
     
     
         23 . The composite particle of  claim 22  wherein one reactant of the two or more reactants is chosen from a group consisting of Al, B, C, and Si and an enhancing alloy is one chosen from a group consisting of Li, K, Na, Mg, or Ca. 
     
     
         24 . A composite particle of  claim 22  whereas a chemistry is chosen so as to lead to a combustion reaction that is dual phase (condensed and vapor). 
     
     
         25 . A composite particle comprising: two elemental or metallic alloy reactants; wherein spacing, composition, and particle size of the two elemental or metallic alloy reactants are controlled such that particles are non-pyrophoric even at particle sizes <30 um, non-toxic, experience low agglomeration compared to nanoaluminum, and/or have a shelf life of over a year. 
     
     
         26 . The composite particle of  claim 25  further comprising a composite particle formed from one element chosen from a group consisting of of Al, B, or Si, plus a second element chosen from a group consisting of Ti, Zr, or Hf, and has an average diameter <100 um. 
     
     
         27 . The composite particle of  claim 25  further formed from reactants that have a spacing between 100 nm and 10 μm, so as to tune a threshold for igniting the exothermic formation reaction.