Crystallization and Stabilization in the Synthesis of Microcrystalline Alpha Alane

Abstract

Systems and methods for producing microcrystalline alpha alane are provided herein. An exemplary process comprises the elimination of the crystallization aid lithium borohydride through the use of excess lithium aluminum hydride or sodium borohydride. Further exemplary processes comprise methods for passivating microcrystalline alpha alane using a weak acid in a nonaqueous solvent solution.

What is claimed is: 
     
         1 . A method for stabilizing aluminum hydride, comprising:
 producing aluminum hydride;   placing the aluminum hydride in a nonaqueous solvent;   adding a weak acid solution to the nonaqueous solvent and allow the aluminum hydride to contact the weak acid solution for a period of time to form passivated aluminum hydride;   separating the passivated aluminum hydride from the solvent and weak acid solution; and   washing and drying the passivated aluminum hydride.   
     
     
         2 . The method of  claim 1 , wherein the nonaqueous solvent comprises an aromatic solvent, a hydrocarbon solvent, or mixtures thereof. 
     
     
         3 . The method of  claim 1 , wherein the nonaqueous solvent comprises toluene. 
     
     
         4 . The method of  claim 1 , wherein the weak acid comprises an acid with a dissociation constant less than that of hydrochloric acid. 
     
     
         5 . The method of  claim 1 , wherein the weak acid comprises an acid that partially dissociates in water. 
     
     
         6 . The method of  claim 1 , wherein the step of forming passivated aluminum hydride further comprises cooling the weak acid solution and the nonaqueous solvent. 
     
     
         7 . The method of  claim 1 , wherein the step of separating the passivated aluminum hydride from the solvent and weak acid solution further comprises filtering the aluminum hydride from the solvent and weak acid solution, washing the aluminum hydride with water, and washing the aluminum hydride with alcohol. 
     
     
         8 . The method of  claim 1 , wherein the step of drying the passivated aluminum hydride further comprises heating the passivated aluminum hydride. 
     
     
         9 . The method of  claim 8 , further comprising heating the passivated aluminum hydride under vacuum. 
     
     
         10 . The method of  claim 1 , wherein the aluminum hydride comprises alpha alane.