Method for producing metal-based materials for magnetic cooling or heat pumps

Abstract

The process for preparing metal-based materials for magnetic cooling or heat pumps comprises the following steps: a) reacting chemical elements and/or alloys in a stoichiometry which corresponds to the metal-based material in the solid phase and/or liquid phase, b) if appropriate converting the reaction product from stage a) to a solid, c) sintering and/or heat treating the solid from stage a) or b), d) quenching the sintered and/or heat treated solid from stage c) at a cooling rate of at least 100 K/s.

1 . A process for preparing a metal-comprising material, the process comprising:
 a) reacting at least one chemical element and/or at least one alloy in a stoichiometry which corresponds to the metal-comprising material, in solid phase and/or liquid phase, to yield a first reaction product;   b) optionally., converting the first reaction product from a) to a solid;   c) sintering and/or heat treating the first reaction product from a) or the solid from b), to give a second solid; and   d) quenching the second solid from c) at a cooling rate in a range from 200 to 1300 K/s.   
     
     
         2 . The process according to  claim 1 , wherein the reacting in a) is effected by heating the at least one element and/or alloy together in a closed vessel or in an extruder, or by solid phase reaction in a ball mill. 
     
     
         3 . The process according to  claim 1 , wherein the converting to a solid in b) is effected by melt spinning or spray cooling. 
     
     
         4 . The process according to  claim 1 , wherein, in c), first sintering is effected at a temperature in a range from 800 to 1400° C. and then heat treating at a temperature in a range from 500 to 750° C. 
     
     
         5 . The process according to  claim 1 , wherein the metal-comprising is at least one selected from the group consisting of
 (1) a compound of formula (I)
   (A y B y     −     1 ) 2+δ C w D x E z   (I),
 
   
       wherein
 A is Mn or Co, 
 B is Fe, Cr, or Ni, 
 C, D, E at least two of C, D, E are different, have a non-vanishing concentration and are selected from the group consisting of P, B, Se, Ge, Ga, Si, Sn, N, As, and Sb, whereby at least one of C, D, and E is Ge or Si, 
 δ is a number in a range from −0.1 to 0.1, 
 w, x, y, z are numbers in a range from 0 to 1, whereby w+x+z=1; 
 (2a) an La- and Fe-based compound of formulae (II)
   La(Fe x Al 1−x ) 13 H y  or La(Fe x Si 1−z ) 13 H y   (II),
 
 
 
       wherein
 x is a number from 0.7 to 0.95, and 
 y is a number from 0 to 3; 
 (2b) an La- and Fe-based compound of formula III
   La(Fe x Al y Co z ) 13  or La(Fe x Si y Co z ) 13   (III),
 
 
 
       wherein
 x is a number from 0.7 to 0.95, 
 y is a number from 0.05 to 1−x, and 
 z is a number from 0.005 to 0.5; 
 (2c) an La- and Fe-based compound of formula IV
   LaMn x Fe 2−x Ge  (IV),
 
 
 
       wherein
 x is a number from 1.7 to 1.95; and 
 (3) a Heusler alloy of MnTP composition, wherein T is a transition metal and P is a p-doping metal with an electron count per atom, e/a, in a range from 7 to 8.5. 
 
     
     
         6 . The process according to  claim 5 , wherein the metal-comprising material is at least one at least quaternary compound of formula (I) which, as well as Mn, Fe, P, and optionally Sb, additionally comprises
 Ge or Si or As, or   Ge and As, or   Si and As, or   Ge, Si and As.   
     
     
         7 . The process according to  claim 1 , wherein
 a) is a solid phase reaction of the at least one element and/or alloy in a ball mill, to give a first material;   b) is melt spinning the first material obtained in a) to give a second solid;   c) is heat treating the second solid from b) at a temperature in a range from 430 to 1200° C., for a period of from 10 seconds or 1 minute to 5 hours, to give a heat treated shaped body; and   d) is quenching the heat treated shaped body from c) at a cooling rate of from 200 to 1300 K/s.   
     
     
         8 . (canceled) 
     
     
         9 . A metalized material, obtained by a process as defined in  claim 5 , excluding As-comprising materials, with an average crystal size in a range from 10 to 400 nm. 
     
     
         10 . (canceled) 
     
     
         11 . The process according to  claim 2 , wherein the converting to a solid in b) is effected by melt spinning or spray cooling. 
     
     
         12 . The process according to  claim 2 , wherein, in c), first sintering is effected at a temperature in a range from 800 to 1400° C. and then heat treating at a temperature in a range from 500 to 750° C. 
     
     
         13 . The process according to  claim 3 , wherein, in c), first sintering is effected at a temperature in a range from 800 to 1400° C. and then heat treating at a temperature in a range from 500 to 750° C. 
     
     
         14 . The process according to  claim 11 , wherein, in c), first sintering is effected at a temperature in a range from 800 to 1400° C. and then heat treating at a temperature in a range from 500 to 750° C.