Method for fabricating a functionally-graded monolithic sintered working component for magnetic heat exchange and an article for magnetic heat exchange

A method for fabricating a functionally-graded monolithic sintered working component for magnetic heat exchange, comprising:

• providing a plurality of powders comprising elements in amounts sufficient for forming a La1-aRa(Fe1-x-yTyMx)13HzCb phase with a NaZn13 structure, wherein T is one or more of the elements selected from the group consisting of Mn, Co, Ni, Ti, V and Cr, M is one or more of the elements selected from the group consisting of Si and Al, and R is one or more of the elements selected from the group consisting of Ce, Nd, Y and Pr, wherein a is such that 0≤a≤0.5, b is such that 0≤b≤1.5, x is such that 0.05≤x≤0.2, y is such that 0≤y≤0.2, and z is such that 0≤z≤3;
• mixing the powders with a liquid and optionally with a binder and/or a dispersant to form a green body in the form of a slurry or paste in which an amount of at least one element selected from the group consisting of T, R, C and M varies in a pre-determined direction,
• heat treating the green body at a temperature T and for a time t selected to allow diffusion of one or more of the elements selected from the group consisting of T, R and C, and
• forming a working component from the green body comprising a Curie temperature that monotonically increases or monotonically decreases in the pre-determined direction, and wherein a gradient of the increase or decrease does not exceed 10° C./0.5 mm anywhere in the working component.

A method for fabricating a functionally-graded monolithic sintered working component for magnetic heat exchange, comprising:

• providing a plurality of powders comprising elements in amounts sufficient for forming a La1-aRa(Fe1-x-yTyMx)13HzCb phase with a NaZn13 structure, wherein T is one or more of the elements selected from the group consisting of Mn, Co, Ni, Ti, V and Cr, M is one or more of the elements selected from the group consisting of Si and Al, and R is one or more of the elements selected from the group consisting of Ce, Nd, Y and Pr, wherein a is such that 0≤a≤0.5, b is such that 0≤b≤1.5, x is such that 0.05≤x≤0.2, y is such that 0≤y≤0.2, and z is such that 0≤z≤3;
• mixing the powders with a liquid and optionally with a binder and/or a dispersant to form a green body in the form of a slurry or paste in which an amount of at least one element selected form the group consisting of T, R, C and M varies in a pre-determined direction, the slurry or paste having a viscosity between 200 mPas and 100,000 mPas,
• heat treating the green body at a temperature T and for a time t selected to allow diffusion of one or more of the elements selected from the group consisting of T, R and C,
• forming a working component from the green body comprising a Curie temperature that monotonically increases or monotonically decreases in the pre-determined direction.

A method for fabricating a functionally-graded monolithic sintered working component for magnetic heat exchange, comprising:

• providing a plurality of powders comprising elements in amounts sufficient for forming a La1-aRa(Fe1-x-yTyMx)13HzCb phase with a NaZn13 structure, wherein T is one or more of the elements selected from the group consisting of Mn, Co, Ni, Ti, V and Cr, M is one or more of the elements selected from the group consisting of Si and Al, and R is one or more of the elements selected from the group consisting of Ce, Nd, Y and Pr, wherein a is such that 0≤a≤0.5, b is such that 0≤b≤1.5, x is such that 0.05≤x≤0.2, y is such that 0≤y≤0.2, and z is such that 0≤z≤3;
• mixing the powders with a liquid and optionally with a binder and/or a dispersant to form a green body in the form of a slurry or paste in which an amount of at least one element selected from the group consisting of T, R, C and M varies in a pre-determined direction,
• applying the slurry or paste to a surface layer by layer to form a stack such that the content of at least one element selected from the group consisting of R, T, C and M increases or decreases in a direction of the stack,
• heat treating the green body at a temperature T and for a time t selected to allow diffusion of one or more of the elements selected from the group consisting of T, R and C,
• forming a working component from the green body comprising a Curie temperature that monotonically increases or monotonically decreases in the pre-determined direction, and wherein a gradient of the increase or decrease does not exceed 10° C./0.5 mm anywhere in the working component.

A method for fabricating a functionally-graded monolithic sintered working component for magnetic heat exchange, comprising:

• providing powder comprising elements in amounts sufficient for forming a La1-aRa(Fe1-x-yTyMx)13HzCb phase with a NaZn13 structure, wherein T is one or more of the elements selected from the group consisting of Mn, Co, Ni, Ti, V and Cr, M is one or more of the elements selected from the group consisting of Si and Al, and R is one or more of the elements selected from the group consisting of Ce, Nd, Y and Pr, wherein a is such that 0≤a≤0.5, b is such that 0≤b≤1.5, x is such that 0.05≤x≤0.2, y is such that 0≤y≤0.2, and z is such that 0≤z≤3;
• mixing the powders with a liquid and optionally with a binder and/or a dispersant to form a green body in the form of a slurry or paste in which an amount of at least one element selected from the group consisting of T, R, C and M varies in a pre-determined direction,
• applying the slurry or paste to a surface layer by layer to form a stack, each layer in the stack having a thickness of 10 μm to 60 μm,
• heat treating the green body at a temperature T and for a time t selected to allow diffusion of one or more of the elements selected from the group consisting of T, R and C, and
• forming a working component comprising a Curie temperature that monotonically increases or monotonically decreases in the pre-determined direction.