Abstract:
Insensitive, high performance explosives obtained by combining certain  enetic, high density inorganic compounds with insensitive, underoxidized organic nitro compounds.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention. 
     This invention relates to insensitive, high performance explosives. 
     2. Description of the Prior Art. 
     The use of organic nitro compounds as explosives is well known. These compounds are self-oxidizing, i.e., the nitro groups provide the oxygen used in oxidation. 
     The highest detonation pressures achievable with the currently used organic nitro compounds are about 390 kbar. Further, the best performers (those from which detonation pressures approaching 390 Kbar are achievable) are highly sensitive. Thus, the use of the highest performing organic nitro compounds as explosives is risky and impractical. On the other hand, the lower performing explosives which possess acceptable stability are, without exception, underoxidized and generally exhibit low densities. The densities of the stable explosives are generally less than two grams per cm 3 . These two factors, i.e., the underoxidized nature of the stable organic nitro compounds and their low densities, severely limit their performance. 
     SUMMARY OF THE INVENTION 
     It has now been found that the performance of explosives based on commonly used organic nitro compounds can be increased to about 530 kbar by adding certain dense and stable but highly energetic inorganic oxidizers. Among the suitable oxidizers are: (NF 4 ) 2  TiF 6 , NF 4  BF 4 , Ti(ClO 4 ) 4 , (NF 4 ) 2  NiF 6  and other hereinafter named compounds. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Typical examples of performance increases achievable by the use of the inorganic oxidizers of this invention are illustrated in the following table. 
     
                       TABLE______________________________________ Examples of TheoreticalPerformance Improvements                        DetonationSystem             Weight %  Pressure (kb)______________________________________Nitroquanidine (NQ)              100       255NQ + (NF.sub.4).sub.2 TiF.sub.6              43-57     349Triaminotrinitrobenzene (TATB)              100       280TATB + NF.sub.4 BF.sub.4              29-71     375TATB + (NF.sub.4).sub.2 TiF.sub.6              30-70     408HMX                100       382HMX + NF.sub.4 BF.sub.4              51-49     449HMX + Ti (C10.sub.4).sub.4              70-30     456HMX + (NF.sub.4).sub.2 TiF.sub.6              52-48     471HMX + (NF.sub.4).sub.2 NiF.sub.6              56-44     527______________________________________ 
    
     The detonation pressures set forth in the foregoing table were calculated by means of the Kamlet correlation (J. Chem. Phys., 48, 23 (1968)), a method commonly used for the performance evaluation of explosives. The percentage of oxidizer used was chosen to obtain complete combustion of the organic nitro compound (to CO 2 , N 2  and HF in the case of HMX or NQ and to COF 2 , N 2  and HF in the case of TATB). As can be seen from the table, the performance of organic nitro explosives is significantly increased by the addition of dense energetic inorgaic oxidizers. 
     Laboratory tests have shown that the oxidizers and explosives are mutually compatible. For example, HMX and NF 4  BF 4  were found to be stable at 150° C. and drop weight tests of the HMX/NF 4  BF 4  mixtures showed only a moderate increase in sensitivity over that of pure HMX. 
     The examples given in the above table are illustrative only and are not intended to limit the scope of the invention. Other commonly used, underoxidized organic nitro compounds of suitable stability could be substituted for the explosives given as examples in the table. Similarly, other inorganic oxidizers could be substituted for those listed in the table. 
     The primary requirements for suitable oxidizers are high energy content, high density, high thermal stability and low reactivity with the organic nitro compounds. From this point of view, NF 4  + containing salts are ideally suited. The NF 4  +cation is isoelectronic with the extremely inert CF 4  molecule and, therefore, in spite of its high energy content, a relatively high activation energy is required to cause it to react with other compounds. 
     The concept of this invention is not limited to fluorine containing oxidizers. As can be seen from the example of Ti(ClO 4 ) 4  in the table, this fluorine-free oxidizer is equally useful. By analogy with the NF 4  + salts, Ti(ClO 4 ) 4  possesses all the necessary properties for use as an explosive ingredient. 
     Although oxygen containing oxidizers will be as effective as fluorine containing oxidizers in most explosives, fluorine containing oxidizers are advantageous in aluminized formulations. The addition of aluminum is known to increase the performance of an explosive, but the Al 2  O 3  combustion product formed in a fluorine-free system may not remain for a long enough time in the gas phase. AlF 3 , on the other hand, is formed as a combustion product when fluorine containing oxidizers are used. Since AlF 3  (sublimation point 1270° C.) is much more volatile than Al 2  O 3  (boiling point 2250° C.), the use of fluorine containing oxidizers offers a distinct advantage for aluminized systems in that efficiencies higher than those obtainable with oxygen containing oxidizers are achieved. 
     It has been stated above that the oxidizers listed in the table are illustrative only. Examples of other suitable oxidizers are NF 4  + salts such as: NF 4  Sb 3  F 16 , NF 4  SbF 6 , NF 4  HF 2 , NF 4  BiF 6 , NF 4  PF 6 , NF 4  GeF 5 , NF 4  AsF 6 , NF 4  Ti 2  F 9 , NF 4  Ti 3  F 13 , NF 4  Ti 6  F 25 , (NF 4 ) 2  SnF 6  and NF 4  SnF 5  and other metal perchlorates. 
     The salts disclosed herein are not soluble in organic nitro compounds so their use in liquid explosives in conjunction with liquid organic compounds is not possible. However, they may be used in plastic bonded (solid) explosives of the type wherein explosive ingredients are bound in a suitable binder (many of which are known in the art) and in slurries where oxidizer particles are suspended in liquid organic nitro compounds.