Silicide compositions containing alkali metals and methods of making the same

Abstract

The invention relates to a method of making alkali metal silicide compositions, and the compositions resulting from the method, comprising mixing an alkali metal with silicon and heating the resulting mixture to a temperature below about 475° C. The resulting compositions do not react with dry O 2 . Also, the invention relates to sodium silicide compositions having a powder X-ray diffraction pattern comprising at least three peaks with 2Theta angles selected from about 18.2, 28.5, 29.5, 33.7, 41.2, 47.4, and 56.2 and a solid state 23 Na MAS NMR spectra peak at about 18 ppm. Moreover, the invention relates to methods of removing a volatile or flammable substance in a controlled manner. Furthermore, the alkali metal silicide compositions of the invention react with water to produce hydrogen gas.

The claimed invention is: 
     
         1 . A method of removing a volatile or flammable substance in a controlled manner, the volatile or flammable substance being in the presence of water, the method comprising the step of:
 exposing the volatile or flammable substance to an alkali metal silicide composition,   wherein the alkali metal silicide composition is a sodium silicide powder or a potassium silicide powder; and   wherein the alkali metal silicide composition is stable in dry air and reacts exothermically with the water causing a controlled burn, thereby removing the volatile or flammable substance.   
     
     
         2 . A method of  claim 1 , wherein the alkali metal silicide composition comprises Na 4 Si 4  or K 4 Si 4 . 
     
     
         3 . A method of  claim 1 , wherein the molar ratio between the alkali metal and the silicon in the alkali metal silicide composition is about 1:1. 
     
     
         4 . A method of  claim 1 , wherein an exothermic reaction between the alkali metal silicide composition and the water consumes the volatile or flammable substance. 
     
     
         5 . A method of  claim 1 , wherein an exothermic reaction between the alkali metal silicide composition and the water cleans the volatile or flammable substance. 
     
     
         6 . A method of removing a volatile or flammable substance in a controlled manner, the method comprising the steps of:
 exposing the volatile or flammable substance to an alkali metal silicide composition; and   exposing the alkali metal silicide composition to water,   wherein the alkali metal silicide composition is a sodium silicide powder or a potassium silicide powder; and   wherein the alkali metal silicide composition is stable in dry air and reacts exothermically with the water causing a controlled burn, thereby removing the volatile or flammable substance.   
     
     
         7 . A method of  claim 6 , wherein the alkali metal silicide composition comprises Na 4 Si 4  or K 4 Si 4 . 
     
     
         8 . A method of  claim 6 , wherein the molar ratio between the alkali metal and the powdered silicon in the alkali metal silicide composition is about 1:1. 
     
     
         9 . A method of  claim 6 , wherein an exothermic reaction between the alkali metal silicide composition and the water consumes the volatile or flammable substance. 
     
     
         10 . A method of  claim 6 , wherein an exothermic reaction between the alkali metal silicide composition and the water cleans the volatile or flammable substance. 
     
     
         11 . A method of making an alkali metal silicide composition comprising the steps of:
 mixing an alkali metal selected from sodium and potassium with powdered silicon in an inert atmosphere; and   heating the resulting mixture to a temperature from 150° C. up to 500° C.,   wherein the alkali metal silicide composition is stable in dry air and reacts with water; and   wherein the alkali metal silicide composition is a sodium silicide powder or a potassium silicide powder.   
     
     
         12 . A method of  claim 11 , wherein the alkali metal silicide composition comprises Na 4 Si 4  or K 4 Si 4 . 
     
     
         13 . A method of  claim 11 , wherein the molar ratio between the alkali metal and the powdered silicon is about 1:1. 
     
     
         14 . A composition comprising a containment material and an alkali metal silicide composition. 
     
     
         15 . A composition of  claim 14 , wherein the alkali metal silicide composition is a sodium silicide composition selected from:
 an air stable sodium silicide composition having a powder X-ray diffraction pattern comprising peaks at 2Theta angles of about 18.2 and about 41.2 and at least one peak with a 2Theta angle selected from about 28.5, 29.5, 33.7, 47.4, and 56.2;   an air stable sodium silicide composition having a single peak in the solid state 23Na MAS NMR spectra at about 18 ppm; and   an air stable sodium silicide composition that does not react with dry O 2 .   
     
     
         16 . A composition of  claim 15 , wherein the molar ratio between the sodium metal and the silicon is about 1:1. 
     
     
         17 . A composition of  claim 15 , wherein the sodium silicide composition is imbedded or encapsulated in the containment material. 
     
     
         18 . The composition of  claim 17 , wherein the containment material is a foam, a polymer or a porous material. 
     
     
         19 . A method for producing hydrogen gas comprising the step of contacting a composition of  claim 14  with water. 
     
     
         20 . A method of  claim 19 , wherein the containment material delays the release of at least some of the sodium silicide composition from the composition upon contact with the water. 
     
     
         21 . A storage container comprising a water soluble pouch and an alkali metal composition contained within the pouch. 
     
     
         22 . A storage container of  claim 21 , wherein the alkali metal silicide composition is a sodium silicide composition selected from:
 an air stable sodium silicide composition having a powder X-ray diffraction pattern comprising peaks at 2Theta angles of about 18.2 and about 41.2 and at least one peak with a 2Theta angle selected from about 28.5, 29.5, 33.7, 47.4, and 56.2;   an air stable sodium silicide composition having a single peak in the solid state 23Na MAS NMR spectra at about 18 ppm; and   an air stable sodium silicide composition that does not react with dry O 2 .   
     
     
         23 . A method for producing hydrogen gas comprising the step of contacting a storage container of  claim 21  with water. 
     
     
         24 . A method of  claim 23 , wherein the water soluble pouch delays the release of at least some of the alkali metal silicide composition from the container upon contact with the water.