METHOD OF FABRICATING AN ARTICLE FOR MAGNETIC HEAT EXCHANGER
A method of fabricating an article for magnetic heat exchange is provided. The method comprises mixing a binder comprising a poly (alkylene carbonate) and powder comprising a magnetocalorically active phase with a NaZn 13 -type crystal structure to produce a brown body or powder comprising elements in amounts suitable to produce a magnetocalorically active phase with a NaZn 13 -type crystal structure, removing the binder from the brown body to produce a green body, and sintering the green body to produce an article for magnetic heat exchange.
1 . A method of fabricating an article for magnetic heat exchange, comprising:
mixing a binder comprising a poly (alkylene carbonate) and powder comprising a magnetocalorically active phase with a NaZn 13 -type crystal structure or powder comprising elements in amounts suitable to produce a magnetocalorically active phase with a NaZn 13 -type crystal structure and producing a brown body;
removing the binder from the brown body and producing a green body;
sintering the green body, and producing an article for magnetic heat exchange.
2 . The method according to claim 1 , wherein the poly (alkylene carbonate) comprises a decomposition temperature of less than 300° C.
3 . The method according to claim 1 , wherein the polyalklylene carbonate comprises one of the group consisting of poly (ethylene carbonate), poly (propylene carbonate), poly (butylene carbonate) and poly (cyclohexene carbonate).
4 . The method according to claim 1 , wherein the mixture comprises 0.1 weight percent to 10 weight percent binder.
5 . The method according to claim 1 , wherein the removing the binder comprises heat treating the brown body at a temperature of less than 400° C.
6 . The method according to claim 5 , wherein the heat treating the brown body is carried out in at least one of the group consisting of a noble gas atmosphere, a hydrogen-containing atmosphere and vacuum.
7 . The method according to claim 1 , wherein the removing the binder is carried out for 30 min to 20 hour.
8 . The method according to claim 1 , wherein at least 90% by weight of the binder, preferably more than 95 weight percent, is removed.
9 . The method according to claim 1 , further comprising mixing a solvent with the binder and the powder.
10 . The method according to claim 9 , further comprising removing the solvent from the precursor article and producing the brown body.
11 . The method according to claim 10 , wherein the removing the solvent comprises drying the precursor article at a temperature of less than 100 C.
12 . The method according to claim 9 , wherein the solvent comprises one of the group consisting of 2,2,4-Trimethylpentane, isopropanol, 3 Methoxy-1-butanol, propylacetate, dimethyl carbonate and methylethylketone.
13 . The method according to claim 9 , wherein the binder is Polypropylene carbonate and the solvent is methylethylketone.
14 . The method according to claim 1 , further comprising mechanically forming the brown body.
15 . The method according to claim 14 , wherein the mechanically forming the brown body comprises one of the group consisting of injection molding, extrusion, foil casting, screen printing, three-dimensional screen printing and calendaring.
16 . The method according to claim 14 , wherein the mechanically forming the brown body comprises fluidized bed granulisation.
17 . The method according to claim 14 , wherein the mechanically forming the brown body comprises extruding the brown body to form a rod, singulating the rod to form a plurality of brown bodies and rounding the plurality of brown bodies.
18 . The method according to claim 1 , wherein the sintering the green body comprises heat treating at a temperature between 900° C. and 1200° C.
19 . The method according to claim 18 , wherein the sintering is carried out in a noble gas atmosphere, a hydrogen-containing atmosphere or in vacuum.
20 . The method according to claim 18 , wherein the sintering is carried out for a total sintering time t tot , wherein the green body is sintered in vacuum for 0.95t tot to 0.75t tot and subsequently in a noble gas or hydrogen-containing atmosphere for 0.05t tot to 0.256t tot .
21 . The method according to claim 1 , wherein the magnetocalorically active phase is La 1-a R a (Fe 1-x-y T y M x ) 13 H z C b wherein M is Si and, optionally, Al, T is one or more of the elements from the group consisting of Mn, Co, Ni, Ti, V and Cr and R is one or more of the elements from the group consisting of Ce, Nd, Y and Pr, wherein 0≦a≦0.5, 0.05≦x≦0.2, 0.003≦y≦0.2, 0≦z≦3 and 0≦b≦1.5.
22 . The method according to claim 21 , wherein 1.2≦z≦3.
23 . The method according to claim 21 , wherein 0.005≦a≦0.5.