Gas sorbents on the basis of intermetallic compounds and a method for producing the same

Abstract

The present invention relates to new gas sorbents on the basis of intermetallic compounds and a method for producing the same. The method comprises the following steps: mixing and melting of initial metals and homogenization of the melt under negative pressure of inert gas, manufacturing of cast shot by quenching of melted droplets under positive pressure, obtaining of skeleton-type granules by evaporation of the excess of the component A from cast shot under vacuum.

1 . Gas sorbents on the basis of intermetallic compounds with high surface area of the formula A n Me m , where component A is a volatile metal and Me is a non-toxic nonvolatile metal, and where n≧m, in the form of an isolated dendrite carcass, separated from a rapidly solidified heterogeneous alloy with the help of sublimation of its volatile fraction, the intermetallic compounds of the alloy being obtainable by a method comprising the following steps: 
 mixing and melting of initial metals and homogenization of the melt under negative pressure of inert gas,    manufacturing of cast shot by quenching of melted droplets under positive pressure,    obtaining of skeleton-type granules by evaporation of the excess of the component A from cast shot under vacuum.    
   
   
       2 . Gas sorbents according to  claim 1 , wherein the melted droplets containing a certain excess of component A over a stoichiometric composition are subjected to quenching in liquid argon, then as a result of crystallization of a structure occurs consisting of a dendritic carcass A n Me m  and an eutectic, which fills the space between the dendrite arms.  
   
   
       3 . Gas sorbents according to  claim 1 , wherein component A in formula A n Me m  is a chemically active metal selected from the group consisting of alkaline metals, earth alkaline metals, lanthanide metals, actinide metals, especially from the group consisting of Ca, Sr, Li, Mg, Ba.  
   
   
       4 . Gas sorbents according to  claim 3 , wherein component A in formula A n Me m  is calcium or strontium.  
   
   
       5 . Gas sorbents according to  claim 1 , wherein Me in formula A n Me m  is selected from the group of metals consisting of Ag, Al, Cu, Fe, Ga, Ge, In, Ni, Si, Sn, Ta, Ti, Zr.  
   
   
       6 . Gas sorbents according to  claim 1 , wherein the intermetallic compounds are selected from the group consisting of Ca 3 Ag, Ca 2 Cu, Ca 28 Ga 11 , Ca 3 In, Ca 2 Si, Ca 2 Ge, Ca 2 Sn, Sr 3 Ag 2 , SrCu, Sr 8 Al 7 , Sr 8 Ga 7 , Sr 3 In, Sr 2 Si, Sr 2 Ge, Sr 2 Sn and SrNi.  
   
   
       7 . A method for producing high-purity metallic gas sorbents on the basis of intermetallic compounds of the formula  
       A n Me m    
     which are in a thermodynamic equilibrium with the component A forming with it an eutectic and in which A is a chemically active volatile metal, Me is a non-toxic non-volatile metal, and n≧m, starting from chemically active metals or alloys, said method comprising the following steps: 
 mixing and melting of initial metals and homogenization of the melt under negative pressure of inert gas,  
 manufacturing of cast shot by quenching of melted droplets under positive pressure,  
 obtaining of skeleton-type granules by evaporation of the excess of the component A from cast shot under vacuum,  
 packaging of the product by sealing it off in a container under vacuum or under negative pressure of an inert gas.  
 
   
   
       8 . The method according to  claim 7 , wherein the inert gas is argon.  
   
   
       9 . The method according to  claim 7 , wherein the melted droplets containing a certain excess of component A over a stoichiometric composition are subjected to quenching in liquid argon, then as a result of crystallization of a structure occurs consisting of a dendritic carcass A n Me m  and an eutectic, which fills the space between the dendrite arms.  
   
   
       10 . The method according to  claim 7 , wherein component A in formula A n Me m  is selected from the group consisting of alkaline metals, earth alkaline metals, lanthanide metals, actinide metals, especially from the group consisting of Ca, Sr, Li, Na, Mg, Ba.  
   
   
       11 . The method according to  claim 7 , wherein Me in formula A n Me m  is selected from the group of metals consisting of Ag, Al, Cu, Fe, Ga, Ge, In, Ni, Si, Sn, Ta, Ti, Zr.  
   
   
       12 . The method according to  claim 7 , wherein the intermetallic compounds are selected from the group containing Ca and Sr as component A in formula A n Me m  consisting of Ca 3 Ag, Ca 2 Cu, Ca 28 Ga 11 , Ca 3 In, Ca 2 Si, Ca 2 Ge, Ca 2 Sn, Sr 3 Ag 2 , SrCu, Sr 8 Al 7 , Sr 8 Ga 7 , Sr 3 In, Sr 2 Si, Sr 2 Ge, Sr 2 Sn, SrNi.  
   
   
       13 . The method according to  claim 7 , wherein the metal A is melted in an atmosphere of pure argon under pressure of about 1 to 100 mbar with the help of inductive heating while maintaining below the crucible a slightly excessive pressure.  
   
   
       14 . The method according to  claim 7 , wherein the parameters of the sublimation process are defined from the phase diagrams and thermodynamic data on A-Me alloys, wherein the volatilization temperature is limited by the subsolidus area and by the pressures at which decomposition of A n Me m  crystals does not take place.  
   
   
       15 . The method according to  claim 7 , wherein the additional thermal treatment of the cast shot consists of a sublimation for removal of a volatile phase A from the material for obtaining of a skeleton-type structure of isolated intermetallic compounds.  
   
   
       16 . The method according to  claim 7 , wherein the condensation of liquid argon at positive pressure is in the pressure range from 1 to 5 bar in order to obtain a sufficient volume of quenching liquid.  
   
   
       17 . Gas sorbents obtainable by the method of  claim 7 .  
   
   
       18 . An apparatus for carrying out the method according to  claim 7 , said apparatus comprising: 
 a charging compartment (I) comprising a glove box and a doser ( 4 ) for charging and mixing of initial metals or components,    a melting compartment (II) comprising a crucible ( 6 ), wherein the initial metals or components, previously subjected to deep outgassing, are introduced, a flight tube ( 20 ),    a quenching compartment (III), where the droplets solidify in liquid argon, a sublimation compartment (IV) comprising a gas collector ( 13 ).