A SINTERING DEVICE HAVING A DIE LINING OF INCREASED THICKNESS

1 . A device having a sintering chamber, the sintering chamber being bordered by the following device parts:

i. a first punch surface of a first punch;

ii. a second punch surface of a second punch; and

iii. an interior surface of a die;

wherein

the punches are adapted and arranged to apply a pressure of at least 1 MPa along a compression axis to a target in the sintering chamber;

the first punch and the second punch are connected to an electrical power source adapted and arranged to provide a current of at least 5 kA;

the first and second punches comprise at least 50 wt. % carbon, based on the total weight of the punch;

the sintering chamber has a cross-sectional width W perpendicular to the compression axis of at least 300 mm;

wherein a layer δ of a carbon material C δ is present at at least part of the interior surface of the die, the δ having a mean thickness D δ determined over the interior surface of the die,

wherein D δ is in the range from 1.1 to 8 mm.

2 . The device according to claim 1 , wherein the layer δ has a standard deviation of thickness D δ in the range from 0.01 to 0.08 mm determined over the interior surface of the die.

3 . The device according to claim 1 , wherein the layer δ is made up of 2 or more stacked sub-layers.

4 . The device according to claim 1 , wherein both punches and the die are at least partially present in a vacuum chamber or in a non-oxidising atmosphere or both.

5 . The device according to claim 1 , wherein the sintering chamber has a diameter D c and the ratio D c :D δ of the diameter De and the mean thickness of the layer D δ is in the range from 100:1 to 350:1.

6 . The device according to claim 1 , wherein one or both of the following are satisfied:

a. a layer ϵ of a carbon material C ε is present at least part of the first punch surface ( 004 );

b. a layer θ of a carbon material C θ is present at least part of the second punch surface.

7 . The device according to claim 1 , wherein one or more of the following are satisfied:

a. The first punch is at least 99% wt. % carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the first punch;

b. the second punch is at least 99% wt. % carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the second punch;

c. The die is at least 99% wt. % carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the die;

d. The δ is at least 99% wt. % carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the δ.

8 . The device according to claim 1 , wherein the die is of a carbon material C y and one or more of the following are satisfied:

a. C δ and C y have a different anisotropy value,

b. C δ and C γ have a different specific conductivity, determined in a direction parallel to the compression axis,

c. C δ and C γ have a different specific conductivity, determined in a direction perpendicular to the interior surface,

d. C δ and C γ have a different specific thermal expansivity, determined in a direction parallel to the compression axis,

e. C δ and C γ have a different specific thermal expansivity, determined in a direction perpendicular to the interior surface,

f. The first carbon material and the second carbon material have a different ash content as determined by ASTM C-561].

9 . A process for the preparation of a ceramic body, comprising the steps:

a. providing a plurality of particles;

b. providing a device according to claim 1 ;

c. introducing the particles into the sintering chamber of the device;

d. applying a pressure P in the range from 1 MPa to 80 MPa and an electrical current I in the range from 1 kA to 100 kA to obtain the ceramic body.

10 . The process according to claim 9 , wherein the particles contain at least 30 wt. % yttrium in any chemical form, based on the total mass of yttrium atoms and the total mass of the particles.

11 . A ceramic body obtainable by a process according to claim 9 .

12 . The ceramic body according to claim 11 , wherein at least one or all of the following are satisfied:

a. A value for density divided by theoretical density that is less than 1.0;

b. An average grain size of less than 5 μm;

c. A standard deviation for the average grain size distribution that is in the range of 1.8±2 μm to 2.2±2 μm.

13 . An assembly comprising a ceramic body according to claim 11 .

14 . The assembly according to claim 13 , the assembly being selected from the group consisting of:

a. A plasma etcher,

b. Plasma processing chamber (etch or deposition processes),

c. A wear plate for a bearing,

d. A mill liner of a grinding mill.

15 . A use of a graphite layer of thickness in the range from 1.1 to 8 mm for preparing a ceramic body having an extension of at least 300 mm by spark plasma sintering.