Thermite ignition and rusty iron regeneration by localized microwaves

Abstract

A method and corresponding devices employ a mixture of at least a metal oxide and a metal which undergoes an exothermic chemical reaction. Microwave radiation is applied to the mixture so as to generate a localized hot spot in the mixture, thereby initiating the exothermic chemical reaction. The use of localized microwave radiation facilitates low power and portable implementations. Devices and techniques for cutting, drilling, welding, material synthesis, generating thrust, and mechanical power and motion are also disclosed.

What is claimed is: 
     
         1 . A method comprising the steps of
 (a) providing a mixture of at least a metal oxide and a metal which undergoes an exothermic chemical reaction; and   (b) applying microwave radiation to the mixture so as to generate a localized hot spot in the mixture, said localized hot spot having at least one dimension smaller than the wavelength of the microwave radiation, thereby initiating the exothermic chemical reaction.   
     
     
         2 . The method of  claim 1 , wherein said exothermic chemical reaction has an ignition temperature in excess of 900 degrees Celsius. 
     
     
         3 . The method of  claim 1 , wherein said exothermic chemical reaction has an ignition temperature in excess of 1400 degrees Celsius. 
     
     
         4 . The method of  claim 1 , wherein said exothermic chemical reaction is a thermite reaction. 
     
     
         5 . The method of  claim 1 , wherein the microwave radiation is generated by a microwave source of power less than 2 kW. 
     
     
         6 . The method of  claim 1 , wherein the microwave radiation is generated by a microwave source of power less than 200 W. 
     
     
         7 . The method of  claim 1 , wherein the microwave radiation is generated by a solid-state microwave source. 
     
     
         8 . The method of  claim 1 , wherein the microwave radiation is generated at one or more frequency in the range of 300 MHz to 300 GHz. 
     
     
         9 . The method of  claim 1 , wherein a total mass of said mixture is less than 10 g. 
     
     
         10 . The method of  claim 1 , wherein a total mass of said mixture is less than 1 g. 
     
     
         11 . The method of  claim 1 , wherein said applying is performed by coupling an evanescent field with the mixture. 
     
     
         12 . The method of  claim 1 , wherein said applying is performed using an open ended waveguide as an applicator. 
     
     
         13 . The method of  claim 1 , wherein said applying is performed using a waveguide terminating at one or more slot as an antenna. 
     
     
         14 . The method of  claim 1 , wherein the mixture is deployed so as to achieve cutting, drilling, or welding of adjacent materials when initiated. 
     
     
         15 . The method of  claim 1 , wherein said applying is performed underwater or in another oxygen free environment. 
     
     
         16 . The method of  claim 1 , wherein the mixture includes rust formed on the surface of an iron-based metal object and a reactive metal such that the chemical reaction is effective to convert said rust to iron. 
     
     
         17 . The method of  claim 1 , wherein the mixture is dynamically added to a reaction region within which the microwave radiation is applied to the mixture during application of the microwave radiation to the mixture. 
     
     
         18 . The method of  claim 1 , wherein the mixture includes at least one gas-generating reagent. 
     
     
         19 . The method of  claim 18 , wherein said applying microwave radiation is performed within a rocket motor arrangement to generate thrust. 
     
     
         20 . The method of  claim 18 , further comprising converting gas pressure to mechanical motion so as to serve as an engine powering a mechanical device. 
     
     
         21 . The method of  claim 1 , wherein said mixture is chosen so that said exothermic reaction performs a self-propagating high-temperature synthesis (SHS) of a porous material. 
     
     
         22 . The method of  claim 1 , wherein the microwave radiation is provided to the mixture via a plurality of applicators. 
     
     
         23 . A method comprising the steps of:
 (a) providing a mixture of at least a metal oxide and a metal which undergoes an exothermic chemical reaction; and   (b) applying microwave radiation to the mixture so as to generate heat within the mixture, thereby initiating the exothermic chemical reaction, wherein said microwave radiation is applied in a manner so as to satisfy at least one of the conditions:
 (i) a hot spot is generated in the mixture, said hot spot having at least one dimension smaller than the wavelength of the microwave radiation; 
 (ii) heat is generated in a region having at least one dimension smaller than the wavelength of the microwave radiation; 
 (iii) a hot spot is generated in a region smaller than a volume of the mixture. 
   
     
     
         24 . A method comprising the steps of:
 (a) providing a mixture of at least a metal oxide and a metal which undergoes an exothermic chemical reaction; and   (b) applying electromagnetic radiation at one or more frequency in the range of 1 MHz to 1 THz to the mixture so as to generate heat within the mixture, thereby initiating the exothermic chemical reaction, said electromagnetic radiation is applied in a manner so as to satisfy at least one of the conditions;
 (i) a hot spot is generated in the mixture, said hot spot having at least one dimension smaller than the wavelength of the electromagnetic radiation; 
 (ii) heat is generated in a region having at least one dimension smaller than the wavelength of the electromagnetic radiation; 
 (iii) a hot spot is generated in a region smaller than a volume of the mixture.