Sintering device with temperature gradient control

Abstract

A method for producing a ceramic body, the method comprising the steps of: a. Providing a plurality of particles; b. Providing a device comprising a sintering chamber (013) delimited by a die (006); c. Introducing the particles into the sintering chamber (013); d. Applying a pressure P in the range of 1 MPa to 80 MPa to the plurality of particles in the sintering chamber (013) to obtain the ceramic body, the temperature in the sintering chamber (013) being controlled during the preparation of the ceramic body such that the temperature at the center of the sintering chamber (013) is lower than the temperature at the inner surface (005) of the die (006).

Description

[0001] describe Technical Field

[0002] The present invention generally relates to sintering under pressure and using an electric current, commonly referred to as spark plasma sintering (SPS). Particular aspects of the present invention relate to sintering apparatus, sintering methods, ceramic body products, assemblies including ceramic bodies, and the use of temperature differentials in sintering methods. Background Art

[0003] Sintering methods provide a way to form a body from particles by applying heat and pressure. In a method generally referred to as spark plasma sintering (SPS), heating is achieved using an electric current. Spark plasma sintering methods in the prior art have been applied to various materials. Existing literature focuses on small-scale systems, providing access to components with physical extensions of up to about 150 mm. Eugene A. Olevsky et al. evaluated the problem of using SPS to prepare larger components from a theoretical perspective in the following literature: "Fundamental Aspects of Spark Plasma Sintering: I. Experimental Analysis of Scalability" (J. Am. Ceram. Soc., 95 [8], 2406 to 2413 (2012)) and "Fundamental Aspects of Spark Plasma Sintering: II. Experimental Analysis of Scalability" (J. Am. Ceram. Soc., 95 [8], 2414 to 2422 (2012)). Several potential challenges and complications associated with large-scale systems were identified. Summary of the invention

[0004] It is an object of the present invention to provide an improved process for preparing ceramic bodies. It is a particular object of the present invention to provide an improved process for preparing ceramic bodies of increased size.

[0005] It is an object of the present invention to provide an improved process for producing ceramic bodies having a reduced energy requirement.

[0006] It is an object of the present invention to provide an improved process for producing ceramic bodies having a reduced scrap rate.

[0007] It is an object of the present invention to provide an improved process for producing ceramic bodies having reduced fracture sensitivity.

[0008] It is an object of the present invention to provide an improved process for producing ceramic bodies having reduced internal stresses.

[0009] It is an object of the present invention to provide an improved process for producing ceramic bodies having increased mechanical strength.

[0010] It is an object of the present invention to provide an improved process for producing ceramic bodies having increased density.

[0011] It is an object of the present invention to provide an improved process for producing ceramic bodies having increased density uniformity.

[0012] It is an object of the present invention to provide an improved process for producing ceramic bodies having increased etching resistance.

[0013] It is an object of the present invention to provide an improved process for producing ceramic bodies having reduced surface roughness.

[0014] The object of the present invention is to provide an apparatus for carrying out the above-mentioned improved method.

[0015] Any embodiment of the present invention contributes to at least partially achieving at least one of the above-mentioned objects.

[0016] A first (1st) embodiment of the present invention is a device having a sintering chamber, which is defined by the following device components:

[0017] i. the inner surface of the first punch of the first punch;

[0018] ii. the inner surface of the second punch of the second punch; and

[0019] iii. the inner surface of the die;

[0020] in:

[0021] The punch is adapted and arranged to apply a pressure of at least 1 MPa, preferably at least 5 MPa, more preferably at least 10 MPa, most preferably at least 15 MPa to the target in the sintering chamber along the compression axis. The punch may be adapted and arranged to apply a pressure of up to 80 MPa or even higher;

[0022] The first punch and the second punch are connected to an electrical power source, preferably adapted and arranged to provide a current of at least 5 kA, preferably at least 10 kA, more preferably at least 50 kA, most preferably at least 60 kA. The electrical power source may be adapted and arranged to provide a current of up to 100 kA or even more;

[0023] Based on the total weight of the punch, the first punch and the second punch comprise at least 50 wt %, preferably at least 90 wt %, more preferably at least 95 wt %, and most preferably at least 99 wt %.

[0024] % carbon;

[0025] The sintering chamber has a width perpendicular to the compression axis of at least 300 mm, preferably at least 500 mm,

[0026] More preferably a cross-sectional width W of at least 700 mm is preferred. W may be up to 2000 mm or more.

[0027] It is preferably not more than 1500 mm, more preferably not more than 900 mm.

[0028] In a preferred embodiment of the apparatus, the apparatus is adapted and arranged to control the temperature in the sintering chamber, more preferably the temperature of the target during sintering.This preferred embodiment is a second embodiment of the invention which preferably depends on the first embodiment of the invention.

[0029] In a preferred embodiment of the device, the device further comprises a first layer of the first kind in physical contact with a surface (preferably an outer surface) of the first punch, wherein the first layer of the first kind has a resistivity in the range of 10 μΩ·m to 260 μΩ·m, preferably in the range of 20 μΩ·m to 240 μΩ·m, and more preferably in the range of 30 μΩ·m to 215 μΩ·m. This preferred embodiment is the third embodiment of the present invention, and the third embodiment preferably depends on any one of the first to second embodiments of the present invention. The given resistivity values ​​are measured at 25°C.

[0030] In a preferred embodiment of the device, the first layer of the first type has a -1 ×K -1 Up to 55W·m -1 ·K -1 In the range of 1W·m -1 ·K -1 Up to 40W·m -1 ·K -1 and more preferably within the range of 4 W·m -1 ·K -1 Up to 36W·m -1 ·K -1 The preferred embodiment is the fourth embodiment of the present invention, and the fourth embodiment is preferably dependent on the third embodiment of the present invention.

[0031] In a preferred embodiment of the device, the first layer of the first species is anisotropic and wherein the first layer of the first species has at least one or all of the following properties:

[0032] a. the resistivity in the first direction is in the range of 10 μΩ·m to 70 μΩ·m, preferably in the range of 20 μΩ·m to 50 μΩ·m, and more preferably in the range of 30 μΩ·m to 40 μΩ·m;

[0033] b. the resistivity in the other direction is in the range of 90 μΩ·m to 260 μΩ·m, preferably in the range of 110 μΩ·m to 240 μΩ·m, and more preferably in the range of 130 μΩ·m to 215 μΩ·m;

[0034] c. Thermal conductivity in the first direction is 20 W·m -1 ·K -1 Up to 55W·m -1 ·K -1 In the range of 25W·m -1 ·K -1 Up to 40W·m -1 ·K -1 and more preferably within the range of 29

[0035] W·m -1 ·K -1 Up to 36W·m -1 ·K -1 within the scope of

[0036] d. The thermal conductivity in the other direction is 0.1 W·m -1 ·K -1 Up to 20W·m -1 ·K -1 In the range of 1W·m -1 ·K -1 Up to 16W·m -1 ·K -1 and more preferably in the range of 4

[0037] W·m -1 ·K -1 Up to 12W·m -1 ·K -1 within the range.

[0038] This preferred embodiment is the fifth embodiment of the invention, which is preferably dependent on any one of the third to fourth embodiments of the invention. In one aspect of the fifth embodiment, all possible combinations of features a. to d. are preferred aspects of this embodiment. These combinations are, for example, a; b; c; d; a+b; a+c; a+d; b+c; b+d; c+d; a+b+c; a+b+d; a+c+d; b+c+d; a+b+c+d. In one aspect of the fifth embodiment, the resistivity values ​​are measured at a temperature of 25°C. In a preferred aspect of the fifth embodiment, the first layer of the first kind comprises carbon fibers. In this aspect, it is preferred that the first direction is parallel to the fiber axis and the other direction is perpendicular to the fiber axis. In one aspect of the fifth embodiment, it is preferred that the first layer of the first kind is arranged so that the other direction is parallel to the compression axis.

[0039] In a preferred embodiment of the device, the first layer of the first species comprises carbon, silicon or a combination thereof. This preferred embodiment is the sixth embodiment of the present invention, which is preferably dependent on any one of the third to fifth embodiments of the present invention. In one aspect of the sixth embodiment, it is particularly preferred that the first layer of the first species comprises carbon, more preferably composite carbon fibers.

[0040] In a preferred embodiment of the device, the thickness of the first layer of the first type is in the range of 20 mm to 60 mm, preferably in the range of 32 mm to 48 mm, and more preferably in the range of 37 mm to 43 mm. This preferred embodiment is the seventh embodiment of the present invention, and the seventh embodiment preferably depends on any one of the third embodiment to the sixth embodiment of the present invention.

[0041] In a preferred embodiment of the device, the resistance of the first layer of the first species is in the range of 0.5 μΩ to 40 μΩ, preferably in the range of 5 μΩ to 25 μΩ, and more preferably in the range of 10 μΩ to 20 μΩ. This preferred embodiment is the eighth embodiment of the present invention, and the eighth embodiment preferably depends on any one of the third to seventh embodiments of the present invention.

[0042] In preferred embodiments of the device, at least one or all of the following apply:

[0043] a. The first layer of the first type is in electrical contact with a surface (preferably an outer surface) of the first punch;

[0044] b. The first layer of the first species is in thermal contact with a surface (preferably an outer surface) of the first punch.

[0045] This preferred embodiment is the ninth embodiment of the present invention, and this ninth embodiment preferably depends on any one of the third embodiment to the eighth embodiment of the present invention. In one aspect of the ninth embodiment, all possible combinations of features a. and b. are preferred aspects of this embodiment. These combinations are, for example, a; b; a+b.

[0046] In a preferred embodiment of the device, the device further comprises an additional layer of the first kind in physical contact with a surface (preferably an outer surface) of the second punch. This preferred embodiment is the tenth embodiment of the present invention, and the tenth embodiment preferably depends on any one of the first embodiment to the ninth embodiment of the present invention.

[0047] In a preferred embodiment of the device, the further layer of the first kind has at least one or all of the following properties:

[0048] a. Resistivity in the range of 10 μΩ·m to 260 μΩ·m, preferably in the range of 20 μΩ·m to 240 μΩ·m, and more preferably in the range of 30 μΩ·m to 215 μΩ·m. The given resistivity values ​​are measured at 25°C;

[0049] b. At 0.1W·m -1 ·K -1 Up to 55W·m -1 ·K -1 In the range of 1W·m -1 ·K -1 Up to 40W·m -1 ·K -1 and more preferably within the range of 4 W·m -1 ·K -1 Up to 36W·m -1 ·K -1 Thermal conductivity in the range of

[0050] c. is anisotropic;

[0051] d. comprising carbon, silicon or a combination of at least two thereof;

[0052] e. a thickness in the range of 20 mm to 60 mm, preferably in the range of 32 mm to 48 mm, more preferably in the range of 37 mm to 43 mm;

[0053] f. A resistance in the range of 0.5 μΩ to 40 μΩ, preferably in the range of 5 μΩ to 25 μΩ, and more preferably in the range of 10 μΩ to 20 μΩ.

[0054] This preferred embodiment is the eleventh embodiment of the invention, which is preferably dependent on the tenth embodiment of the invention. In one aspect of the eleventh embodiment, all possible combinations of features a. to f. are preferred aspects of this embodiment. These combinations are, for example, a; b; c; d; e; f; a+b; a+c; a+d; a+e; a+f; b+c; b+d; b+e; b+f; c+d; c+e; c+f; d+e; d+f; e+f; a+b+c; a+b+d; a+b+e; a+b+f; a+c+d; a+c+e; a+c+f; a+d+e; a+d+f; a+e+f; b+c+d; b+c+e; b+c+f; b+d+e; b+d+f; b+e+f; c+d+e; c+d+f; c+e+f; d+ In one aspect of feature c. of the eleventh embodiment, it is preferred that the further layers of the first species have at least one or all of the characteristics a. to d. listed in the fifth embodiment. In this respect, the preferred aspects of the fifth embodiment are also preferred aspects of the first type of further layer (e.g., the first type of further layer comprises carbon fibers, and preferably the first direction is parallel to the fiber axis, and the further direction is perpendicular to the fiber axis). In one aspect of feature d. of the eleventh embodiment, it is particularly preferred that the first type of further layer comprises carbon, more preferably composite carbon fibers.

[0055] In preferred embodiments of the device, at least one or all of the following apply:

[0056] a. The additional layer of the first type is in electrical contact with a surface (preferably an outer surface) of the second punch;

[0057] b. The further layer of the first kind is in thermal contact with a surface (preferably an outer surface) of the second punch.

[0058] This preferred embodiment is the twelfth embodiment of the present invention, and this twelfth embodiment preferably depends on any one of the tenth to eleventh embodiments of the present invention. In one aspect of the twelfth embodiment, all possible combinations of features a. and b. are preferred aspects of this embodiment. These combinations are, for example, a; b; a+b.

[0059] In a preferred embodiment of the device, the device further comprises a layer of another kind arranged at least partially around the outer surface of the die, and wherein the layer of another kind has a thermal conductivity measured at 1400° C., the thermal conductivity being 0.2 W·m -1 ·K -1 Up to 0.65W·m -1 ·K -1 In the range of 0.3W·m -1 ·K -1 Up to 0.55W·m -1 ·K -1 and further preferably within the range of 0.36 W·m -1 ·K -1 To 0.5W·m -1 ·K -1 This preferred embodiment is the thirteenth embodiment of the present invention, and the thirteenth embodiment preferably depends on any one of the first to twelfth embodiments of the present invention.

[0060] In a preferred embodiment of the device, the additional type of layer has at least one or all of the following properties:

[0061] a. At 0.005 g·cm -3 Up to 0.22 g·cm -3 In the range of 0.02 g·cm -3 to 0.15

[0062] g cm -3 and more preferably in the range of 0.06 g·cm -3 To 0.11 g·cm -3 Density within the range of

[0063] b. The average specific heat capacity measured at 1400°C is 1.40 J·g -1 ℃ -1 to 1.95

[0064] J.g -1 ℃ -1 In the range of 1.52 J·g -1 ℃ -11 Up to 1.80 J·g -1 ℃ -1 and more preferably 1.60 J·g -1 ℃ -1 to 1.72 J·g -1 ℃ -1 within the scope of

[0065] c. Thermal emissivity in the range of 0.7 and 0.99, preferably in the range of 0.85 and 0.99, and more preferably in the range of 0.95 and 0.99.

[0066] This preferred embodiment is the fourteenth embodiment of the invention, which is preferably dependent on the thirteenth embodiment of the invention. In one aspect of the fourteenth embodiment, all possible combinations of features a. to c. are preferred aspects of this embodiment. These combinations are, for example, a; b; c; a+b; a+c; b+c; a+b+c.

[0067] In a preferred embodiment of the device, the additional kind of layer comprises at least one or all of the following:

[0068] a. Natural fibers, synthetic fibers, or a combination thereof. Examples of synthetic fibers are rayon;

[0069] b. Foam, preferably open-cell foam.

[0070] This preferred embodiment is the fifteenth embodiment of the present invention, and this fifteenth embodiment preferably depends on any one of the thirteenth to fourteenth embodiments of the present invention. In one aspect of the fifteenth embodiment, all possible combinations of features a. and b. are preferred aspects of this embodiment. These combinations are, for example, a; b; a+b.

[0071] In a preferred embodiment of the device, the additional type of layer comprises carbon, preferably graphite, ceramic, molybdenum or a combination of at least two of them. This preferred embodiment is the sixteenth embodiment of the invention, which preferably depends on any one of the thirteenth to fifteenth embodiments of the invention. An example of a ceramic is a ceramic comprising alumina zirconia, preferably alumina zirconia fibers.

[0072] In a preferred embodiment of the device, the layer of the additional species covers at least 70% of the outer surface of the die, more preferably at least 80%, even more preferably at least 90%, and further preferably at least 95%. This preferred embodiment is the seventeenth embodiment of the present invention, and the seventeenth embodiment preferably depends on any one of the thirteenth embodiment to the sixteenth embodiment of the present invention.

[0073] In a preferred embodiment of the device, the thickness of the additional layer is in the range of 1 mm to 45 mm, preferably in the range of 5 mm to 35 mm, and more preferably in the range of 10 mm to 27 mm. This preferred embodiment is the eighteenth embodiment of the present invention, and the eighteenth embodiment preferably depends on any one of the thirteenth to seventeenth embodiments of the present invention.

[0074] In preferred embodiments of the device, at least one or all of the following apply:

[0075] a. the thickness of the additional layer measured parallel to the compression axis is in the range of 4 mm to 25 mm, preferably in the range of 7 mm to 17 mm, and more preferably in the range of 10 mm to 14 mm;

[0076] b. The thickness of the further kind of layer measured parallel to the compression axis is in the range of 15 mm to 35 mm, preferably in the range of 20 mm to 30 mm and more preferably in the range of 23 mm to 27 mm.

[0077] This preferred embodiment is the nineteenth embodiment of the present invention, and this nineteenth embodiment preferably depends on any one of the thirteenth to eighteenth embodiments of the present invention. In one aspect of the nineteenth embodiment, all possible combinations of features a. and b. are preferred aspects of this embodiment. These combinations are, for example, a; b; a+b.

[0078] In a preferred embodiment of the apparatus, at least one or all of the following are adapted and arranged to control the temperature in the sintering chamber, more preferably the temperature of the target during sintering:

[0079] a. The first layer of the first category;

[0080] b. an additional layer of the first type;

[0081] c. Another type of layer.

[0082] This preferred embodiment is the twentieth embodiment of the present invention, and this twentieth embodiment preferably depends on any one of the second to nineteenth embodiments of the present invention. In one aspect of the twentieth embodiment, all possible combinations of features a. to c. are preferred aspects of this embodiment. These combinations are, for example, a; b; c; a+b; a+c; b+c; a+b+c.

[0083] In a preferred embodiment of the device, the electrical power source is a rectified DC power source.This preferred embodiment is the twenty-first embodiment of the present invention, which is preferably dependent on any one of the first to twentieth embodiments of the present invention.

[0084] In a preferred embodiment of the device, the electrical power source is adapted and arranged for one or more of the following:

[0085] a. Rectify three-phase AC current into DC current;

[0086] b. Rectify single-phase AC current into DC current.

[0087] This preferred embodiment is the twenty-second embodiment of the present invention, and this twenty-second embodiment preferably depends on any one of the first to twenty-first embodiments of the present invention. In one aspect of the twenty-second embodiment, all possible combinations of features a. and b. are preferred aspects of this embodiment. These combinations are, for example, a; b; a+b.

[0088] In a preferred embodiment of the device, the device comprises one or more additional device components selected from the list consisting of:

[0089] a. Shell;

[0090] b. Vacuum equipment;

[0091] c. Hydraulic piston;

[0092] d. Foil lining at the inner surface of the die.

[0093] This preferred embodiment is the twenty-third embodiment of the present invention, and this twenty-third embodiment is preferably dependent on any one of the first to twenty-second embodiments of the present invention. In one aspect of the twenty-third embodiment, all possible combinations of features a. to d. are preferred aspects of this embodiment. These combinations are, for example, a; b; c; d; a+b; a+c; a+d; b+c; b+d; c+d; a+b+c; a+b+d; a+c+d; b+c+d; a+b+c+d.

[0094] A twenty-fourth (24th) embodiment of the present invention is a method for preparing a ceramic body comprising the steps of:

[0095] a. Providing multiple particles;

[0096] b. Providing a device comprising a sintering chamber defined by the inner surface of the die;

[0097] c. introducing the particles into the sintering chamber;

[0098] d. Applying a pressure P in the range of 1 MPa to 80 MPa to the plurality of particles in the sintering chamber to obtain a ceramic body.

[0099] In a preferred embodiment of the method for preparing a ceramic body, the temperature in the sintering chamber is controlled so that the temperature at the center of the sintering chamber is lower than the temperature at the inner surface of the die. This preferred embodiment is the twenty-fifth embodiment of the present invention, and the twenty-fifth embodiment is preferably dependent on the twenty-fourth embodiment of the present invention. In one aspect of the twenty-fifth embodiment, it is preferred to control the temperature during the preparation of the ceramic body, such as step d. in the twenty-fourth embodiment.

[0100] In a preferred embodiment of the method for preparing a ceramic body, the temperature gradient between the center of the sintering chamber and the inner surface of the die is in the range of 0.005°C / mm to 0.55°C / mm, preferably in the range of 0.02°C / mm to 0.45°C / mm, more preferably in the range of 0.07°C / mm to 0.38°C / mm. This preferred embodiment is the twenty-sixth embodiment of the present invention, and this twenty-sixth embodiment preferably depends on any one of the twenty-fourth to twenty-fifth embodiments of the present invention. In one aspect of the twenty-sixth embodiment, it is preferred that a temperature gradient exists during the preparation of the ceramic body, such as step d. in the twenty-fourth embodiment.

[0101] In a preferred embodiment of the method for preparing a ceramic body, the temperature difference between the center of the sintering chamber and the inner surface of the die is in the range of 1°C to 150°C, preferably in the range of 10°C to 135°C, more preferably in the range of 20°C to 125°C. This preferred embodiment is the twenty-seventh embodiment of the present invention, and the twenty-seventh embodiment preferably depends on any one of the twenty-fourth to twenty-sixth embodiments of the present invention. In one aspect of the twenty-seventh embodiment, it is preferred that there is a temperature difference during the preparation of the ceramic body, such as step d. in the twenty-fourth embodiment.

[0102] In a preferred embodiment of the method for preparing a ceramic body, the sintering chamber is defined by at least one punch having a punch surface, and wherein the electric power density measured at the punch surface, preferably the inner punch surface, is adjusted according to the diameter of the prepared ceramic body. This preferred embodiment is the twenty-eighth embodiment of the present invention, which preferably depends on any one of the twenty-fourth to twenty-seventh embodiments of the present invention. In one aspect of the twenty-eighth embodiment, the electric power density is preferably adjusted before preparing the ceramic body, for example before step d. in the twenty-fourth embodiment.

[0103] In a preferred embodiment of the method for preparing a ceramic body, the electric power density decreases as the diameter of the ceramic body to be prepared increases. This preferred embodiment is the twenty-ninth embodiment of the present invention, and the twenty-ninth embodiment preferably depends on any one of the twenty-fourth to twenty-eighth embodiments of the present invention. In one aspect of the twenty-ninth embodiment, the electric power density is preferably adjusted before preparing the ceramic body, for example, before step d. in the twenty-fourth embodiment.

[0104] In a preferred embodiment of the method for preparing a ceramic body, at least one or all of the following apply:

[0105] a. When the diameter of the ceramic body to be prepared is in the range of >500 mm to 650 mm, the electric power density is adjusted to 0.05 W mm2 Up to 1W·mm 2 In the range of 0.1 W·mm 2 Up to 0.7W·mm 2 and more preferably within the range of 0.3 W·mm 2 Up to 0.5W·mm 2 within the scope of

[0106] b. When the diameter of the ceramic body to be prepared is in the range of 300 mm to 500 mm, the electric power density is adjusted to > 0.1 W mm 2 Up to 1.6W·mm 2 In the range of, preferably >0.3W·mm 2 Up to 1.3W·mm 2 and more preferably >0.5 W·mm 2 Up to 1.0W·mm 2 within the range.

[0107] This preferred embodiment is the 30th embodiment of the present invention, and this 30th embodiment preferably depends on any one of the 24th to 29th embodiments of the present invention. In one aspect of the 30th embodiment, all possible combinations of features a. and b. are preferred aspects of this embodiment. These combinations are, for example, a; b; a+b. In one aspect of the 30th embodiment, it is preferred to adjust the electric power density before preparing the ceramic body, for example, before step d. in the 24th embodiment.

[0108] In a preferred embodiment of the method for preparing a ceramic body, the method further comprises subjecting the prepared ceramic body to a sintering chamber at 100° C. / hour. -1 Up to 165℃·hour -1 In the range of 115℃·hour -1 Up to 150℃·hour -1 and more preferably 125°C·hour -1 Up to 140℃·hour -1 The preferred embodiment is the thirty-first embodiment of the present invention, and the thirty-first embodiment is preferably dependent on any one of the twenty-fourth to thirtieth embodiments of the present invention. In one aspect of the thirty-first embodiment, it is preferred that a cooling step is performed after obtaining the ceramic body in step d. of the twenty-fourth embodiment.

[0109] In a preferred embodiment of the method for preparing a ceramic body, the temperature of the die is controlled. This preferred embodiment is the thirty-second embodiment of the present invention, and the thirty-second embodiment preferably depends on any one of the twenty-fourth embodiment to the thirty-first embodiment of the present invention. In one aspect of the thirty-second embodiment, it is preferred that the temperature is controlled during the preparation of the ceramic body, such as step d. in the twenty-fourth embodiment.

[0110] In a preferred embodiment of the method for preparing a ceramic body, a current I in the range of 1 kA to 100 kA, preferably in the range of 5 kA to 100 kA, more preferably in the range of 10 kA to 100 kA, even more preferably in the range of 50 kA to 100 kA, and further preferably in the range of 60 kA to 100 kA is applied to the device. This preferred embodiment is the thirty-third embodiment of the present invention, and the thirty-third embodiment is preferably dependent on any one of the twenty-fourth to thirty-second embodiments of the present invention.

[0111] In a preferred embodiment of the method for preparing a ceramic body, the particles contain at least 30% by weight, preferably at least 40% by weight, and more preferably at least 45% by weight of yttrium in any chemical form, based on the total mass of yttrium atoms and the total mass of the particles. This preferred embodiment is the thirty-fourth embodiment of the present invention, and this thirty-fourth embodiment preferably depends on any one of the twenty-fourth to thirty-third embodiments of the present invention.

[0112] In a preferred embodiment of the method for preparing a ceramic body, an apparatus according to the present invention is used, and more preferably the apparatus is any one of the first embodiment to the twenty-third embodiment according to the present invention. The preferred embodiment is the thirty-fifth embodiment of the present invention, and the thirty-fifth embodiment preferably depends on any one of the twenty-fourth embodiment to the thirty-fourth embodiment of the present invention.

[0113] The thirty-sixth (36th) embodiment of the present invention is a ceramic body obtained by the method for preparing a ceramic body according to the present invention, preferably a ceramic body obtainable by the method according to any one of the twenty-fourth to thirty-fifth embodiments of the present invention.

[0114] In a preferred embodiment of the ceramic body, at least one or all of the following are satisfied for the ceramic body:

[0115] a. The value of density divided by theoretical density is less than 1.0;

[0116] b. The average grain size is less than 5 μm, preferably less than 4.5 μm, more preferably less than 4 μm, and further preferably 1 μm to 3 μm;

[0117] c. The standard deviation of the average grain size distribution is in the range of 1.2±2 μm to 2.8±2 μm, preferably in the range of 1.6±2 μm to 2.4±2 μm, and more preferably in the range of 1.8±2 μm to 2.2±2 μm.

[0118] This preferred embodiment is the thirty-seventh embodiment of the present invention, and this thirty-seventh embodiment is preferably dependent on the thirty-sixth embodiment of the present invention. In one aspect of the thirty-seventh embodiment, all possible combinations of features a. to c. are preferred aspects of this embodiment. These combinations are, for example, a; b; c; a+b; a+c; b+c; a+b+c. In the thirty-seventh embodiment, in one aspect of feature a., the value of density divided by theoretical density is preferably at least 0.9, more preferably at least 0.95, and further preferably at least 0.99.

[0119] The thirty-eighth (38th) embodiment of the present invention is an assembly comprising a ceramic body according to the present invention, preferably a ceramic body according to any one of the thirty-sixth to thirty-seventh embodiments of the present invention.

[0120] In a preferred embodiment of the assembly, the assembly is selected from the group consisting of:

[0121] a. Plasma etcher,

[0122] b. Plasma processing chamber (etching or deposition method),

[0123] c. Wear plates for load bearing, and

[0124] d. Mill lining of grinding mill.

[0125] The preferred embodiment is the thirty-ninth embodiment of the present invention, and the thirty-ninth embodiment is preferably dependent on the thirty-eighth embodiment of the present invention.

[0126] The fortieth (40th) embodiment of the present invention is the use of a temperature difference for preparing a ceramic body having an extension of at least 300 mm by spark plasma sintering, preferably, the temperature difference is in the range of 5°C to 140°C, preferably in the range of 15°C to 130°C, and more preferably in the range of 25°C to 120°C. In one aspect of the fortieth embodiment, the temperature difference is preferably the temperature difference in the sintering chamber of a spark plasma sintering (SPS) device, more preferably the temperature difference during the preparation of the ceramic body using the SPS device. In one aspect of the fortieth embodiment, the ceramic body preferably has an extension of at least 300 mm, more preferably at least 400 mm, and further preferably at least 550 mm.

[0127] A forty-first (41st) embodiment of the present invention is the use of a layer of the first kind for producing a ceramic body having an extension of at least 300 mm, preferably at least 400 mm, more preferably at least 550 mm by spark plasma sintering.

[0128] A forty-second (42nd) embodiment of the present invention is the use of a further kind of layer for producing a ceramic body having an extension of at least 300 mm, preferably at least 400 mm, more preferably at least 550 mm by spark plasma sintering. DETAILED DESCRIPTION

[0129] The following abbreviations are used in the specification: AC (alternating current), DC (direct current).

[0130] sintering

[0131] The present invention relates to a sintering method. A preferred sintering method produces a body from particles by applying pressure and heat. The heating is preferably performed by applying an electric current.

[0132] Preferably sintering increases the density of the plurality of particles to produce a body. The body preferably has a higher density than the plurality of particles. Preferably sintering produces a product body having a density of at least 95%, preferably at least 99%, more preferably at least 99.9% of its theoretical density.

[0133] Device

[0134] The device of the present invention is suitable and arranged for sintering particles to produce a body. The device comprises at least a first punch, a second punch and a die. The device has a sintering chamber.

[0135] Sintering chamber

[0136] The device of the present invention has a sintering chamber. The sintering chamber is preferably suitable for and arranged to accommodate a plurality of particles. The sintering chamber is preferably defined by a first punch inner surface of the first punch, a second punch inner surface of the second punch, and an inner surface of the die. The sintering chamber may be defined only by the first punch inner surface, the second punch inner surface, and the inner surface, or may be additionally defined by one or more additional surfaces. The sintering chamber is preferably defined only by the first punch inner surface, the second punch inner surface, and the inner surface.

[0137] The sintering chamber may have one or more planes of symmetry or one or more axes of symmetry or both. The sintering chamber may have the form of a volume of revolution. The sintering chamber may be cylindrical.

[0138] Punch

[0139] The device of the present invention has a first punch and a second punch. The first punch has a first punch inner surface defining a sintering chamber. The second punch has a second punch inner surface defining a sintering chamber. Preferably, one or both of the punch inner surfaces are substantially flat.

[0140] The punch is preferably adapted and arranged to apply a force to the target in the sintering chamber, preferably for generating an increased pressure in the sintering chamber. The punch is preferably adapted and arranged to generate a pressure of at least 1 MPa, preferably at least 5 MPa, more preferably at least 10 MPa, most preferably at least 15 MPa in the sintering chamber. The punch may be adapted and arranged to apply a pressure of up to 80 MPa or even higher. The first punch and the second punch are preferably positioned vertically above and below the sintering chamber, respectively. The first punch and the second punch are preferably adapted and arranged to move along the compression axis.

[0141] The punch is preferably electrically conductive. The punch is preferably adapted and arranged to provide a current of at least 5 kA, preferably at least 10 kA, more preferably at least 50 kA, most preferably at least 60 kA across the sintering chamber. The electrical power source may be adapted and arranged to provide a current of up to 100 kA or even greater.

[0142] The punch is preferably made of a carbon material, most preferably graphite. The punch preferably comprises at least 95 wt% carbon, more preferably at least 99 wt%, still more preferably at least 99.5 wt% carbon. The punch may comprise one or more selected from: a layer and a region; made of a material other than carbon.

[0143] Die head

[0144] The device of the present invention has a die head. The die head has an inner surface defining a sintering chamber.

[0145] In one embodiment, the die is electrically conductive. Preferably, the die has anisotropic conductivity, preferably with a material orientation axis substantially aligned with the compression axis.

[0146] In one embodiment, the die comprises one or more elements selected from Group 14 of the periodic table. Group 14 elements are sometimes also referred to as Group IVA elements or Group 4A elements. The die preferably comprises one or more selected from the group consisting of C, Si, Ge, Sn and Pb, preferably selected from C, Si, Ge and Sn, most preferably selected from C and Si. C is the most preferred Group 14 element. In one aspect of this embodiment, the die comprises 50 wt % or more, more preferably 90 wt % or more, most preferably 95 wt % or more of the Group 14 element, based on the total weight of the die.

[0147] In one embodiment, the die comprises at least 50 wt %, preferably 90 wt % or more, more preferably 95 wt % or more, most preferably 99 wt % or more C, based on the total weight of the die. In one aspect of this embodiment, the die additionally comprises one or more additional Group 14 elements, preferably selected from Si, Ge, Sn and Pb, more preferably selected from Si, Ge and Sn, still more preferably selected from Si and Ge, most preferably Si. The other Group 14 elements are preferably present in a total content of at least 0.1 wt %, more preferably at least 1 wt %, most preferably at least 2 wt %. In this embodiment, elements other than C, Si, Ge, Sn and Pb are preferably present in a total content of not more than 1 wt %, more preferably not more than 0.5 wt %, most preferably not more than 0.1 wt %.

[0148] The die is preferably made of a carbon material, most preferably graphite.

[0149] The die can be a single piece or multiple pieces, preferably a single piece. Preferably, the die is a single continuous body, more preferably a single cylinder. The die is preferably present in 2 to 10 pieces, more preferably 2 to 5 pieces, still more preferably 2 to 3 pieces, most preferably 2 pieces.

[0150] The die head may have one or more planes of symmetry or one or more axes of symmetry or both. The sintering chamber may have the form of a volume of revolution. The sintering chamber may be hollow cylindrical.

[0151] orientation

[0152] The device of the invention has a compression axis. The device is preferably adapted and arranged to apply a force to the sintering chamber in the direction of the compression axis.

[0153] Preferably, the first punch is movable along the compression axis. Preferably, the second punch is movable along the compression axis. Preferably, both punches are movable along the compression axis.

[0154] In one embodiment, the compression axis is substantially vertical, preferably, wherein the first punch is positioned above the second punch. In one aspect of this embodiment, the first punch inner surface is preferably the lower surface of the first punch. In another aspect of this embodiment, the first punch inner surface is substantially horizontal. In another aspect of this embodiment, the second punch inner surface is preferably the upper surface of the second punch. In another aspect of this embodiment, the second punch inner surface is substantially horizontal.

[0155] The third type of layer

[0156] In one aspect of the present invention, it is preferred that a third type of layer is present at least a portion of the die inner surface. The third type of layer is preferably a carbon material layer. In aspects where a third type of layer is present, it is preferred that the third type of layer is present at 20% or more of the die inner surface, preferably 50% or more, more preferably 90% or more, most preferably 95% or more, based on the total area of ​​the die inner surface. In aspects where a third type of layer is present, it is most preferred that the third type of layer is substantially present on the entire inner surface of the die.

[0157] In aspects where a third type of layer is present, it is preferred that the third type of layer lines the interior surface of the die, preferably substantially the entire surface of the die.

[0158] In aspects where there is a third type of layer, it is preferred that a first gap exists between the inner surface of the die and the first punch, and the third type of layer exists in at least a portion of the gap, preferably in substantially the entire gap. In aspects where there is a third type of layer, it is preferred that a second gap exists between the inner surface of the die and the second punch, and the third type of layer exists in at least a portion of the gap, preferably in substantially the entire gap.

[0159] In aspects where there is a third type of layer, it is preferred that the third type of layer is a single layer, or has at least two stacked sub-layers. In aspects where there is a third type of layer, it is preferred that the third type of layer preferably has at least two stacked sub-layers, preferably between 2 and 20 stacked sub-layers. In aspects where there is a third type of layer, it is preferred that the single layer or any sub-layer may be present on a portion of the inner periphery of the die, or on substantially the entire inner periphery of the die, or on the entire inner periphery of the die and at least partially overlap itself.

[0160] In aspects where a third type of layer is present, it is preferred that the third type of layer is preferably close to the inner surface of the die, more preferably in physical contact with the inner surface of the die. In aspects where a third type of layer is present, it is preferred that the third type of layer may be a piece that is not integrally connected to the inner surface of the die. This is particularly the case before the sintering process. In aspects where a third type of layer is present, it is preferred that the third type of layer may be integrally connected to the inner surface of the die. This is particularly the case after the sintering process.

[0161] The thickness of the third type of layer is determined as an average value over the entire inner surface of the die.

[0162] In aspects where a third type of layer is present, it is preferred that the third type of layer is a graphite foil. The graphite foil preferably has a plurality of 2D platelets. The graphite foil is preferably arranged to form a roll.

[0163] In aspects where a third type of layer is present, it is preferred that the ash content of the third type of layer is preferably less than 1 wt%, more preferably less than 0.5 wt%, and even more preferably less than 0.4 wt%.

[0164] The first type of layer

[0165] In one aspect of the invention, it is preferred that the device according to the invention comprises a first layer of a first kind in physical contact with a surface of the first punch. In this aspect, it is preferred that the first layer of the first kind is in electrical contact, thermal contact, or both with an inner surface of the first punch. In this aspect, it is more preferred that the first layer of the first kind is in electrical contact, thermal contact, or both with an outer surface of the first punch.

[0166] In another aspect of the invention, it is preferred that the device according to the invention comprises a further layer of the first kind in physical contact with the surface of the second punch. In this aspect, it is preferred that the further layer of the first kind is in electrical contact, thermal contact, or both with the inner surface of the second punch. In this aspect, it is more preferred that the further layer of the first kind is in electrical contact, thermal contact, or both with the outer surface of the second punch.

[0167] In one aspect of the invention, it is preferred that the device according to the invention comprises a first layer of the first kind in physical contact with the surface of the first punch, and a further layer of the first kind in physical contact with the surface of the second punch. In this aspect, it is particularly preferred that the first layer of the first kind is in electrical and thermal contact with the outer surface of the first punch, and the further layer of the first kind is in electrical and thermal contact with the outer surface of the second punch.

[0168] In one aspect of the invention, it is preferred that at least 70%, more preferably at least 80%, and further preferably at least 90% of the surface (preferably the outer surface) of the first punch is in physical contact with the first layer of the first kind. In one aspect of the invention, it is preferred that at least 70%, more preferably at least 80%, and further preferably at least 90% of the surface (preferably the outer surface) of the first punch is in electrical contact with the first layer of the first kind. In one aspect of the invention, it is preferred that at least 70%, more preferably at least 80%, and further preferably at least 90% of the surface (preferably the outer surface) of the first punch is in thermal contact with the first layer of the first kind.

[0169] In one aspect of the invention, it is preferred that at least 70%, more preferably at least 80%, and further preferably at least 90% of the surface (preferably the outer surface) of the second punch is in physical contact with the further layer of the first kind. In one aspect of the invention, it is preferred that at least 70%, more preferably at least 80%, and further preferably at least 90% of the surface (preferably the outer surface) of the second punch is in electrical contact with the further layer of the first kind. In one aspect of the invention, it is preferred that at least 70%, more preferably at least 80%, and further preferably at least 90% of the surface (preferably the outer surface) of the second punch is in thermal contact with the further layer of the first kind.

[0170] In one aspect of the invention, it is preferred that the first type of layer comprises carbon (preferably in the form of carbon fibers), silicon, or a combination of at least two of them. An example of a combination of carbon and silicon is silicon carbide. An example of a combination of carbon and plastic is carbon fiber reinforced plastic.

[0171] In one aspect of the invention, it is preferred that the layers of the first kind are "anisotropic". This should preferably be understood to mean that the value of at least one physical property measured in a first direction is different from the value of at least one physical property measured in another direction. Examples of the at least one physical property are the resistivity and the thermal conductivity of the layers of the first kind. In this aspect, it is preferred that the first direction is perpendicular to the other directions.

[0172] In one aspect of the present invention, preferably, the first type of layer comprises at least two sub-layers stacked on top of each other. In this respect, preferably, the sub-layer has a thickness in the range of 12mm to 28mm, preferably in the range of 17mm to 23mm.

[0173] Layers of the first kind comprising composite carbon fibers are well known to the person skilled in the art. Such layers of the first kind are commercially available from, for example, SGL Carbon SE (Germany) and Cera Materials (USA).

[0174] Another type of layer

[0175] In one aspect of the invention, it is preferred that the device according to the invention comprises a further kind of layer. The outer surface of the die should preferably be understood as any surface of the die that does not define a sintering chamber. In this aspect, it is preferred that the further kind of layer is in physical contact with the outer surface of the die.

[0176] Preferred additional types of layers include at least one or all of the following: carbon felt (e.g., graphite felt), ceramic felt, graphite foam, ceramic foam, or a combination of at least two of them. In this respect, it is particularly preferred that the additional type of layer includes graphite felt. Additional types of layers are well known to those skilled in the art and are commercially available from all major graphite producers such as Mersen SA (France).

[0177] Type of contact

[0178] If two components of the device are in "electrical contact", this should be understood to mean that current can flow between the two components. For example, if a first type of layer is in electrical contact with the surface of the punch, current can flow between the first type of layer and the surface of the punch.

[0179] If two components of the device are in "thermal contact", this should be understood to mean that heat can flow between the two components. For example, if a first type of layer is in thermal contact with the surface of the punch, heat can flow between the first type of layer and the surface of the punch.

[0180] If two components of a device are in "physical contact", this is understood to mean that the two components are in contact with each other. For example, if a layer of a first kind is in physical contact with the surface of a punch, then the layer of the first kind is in contact with the surface of the punch. For example, if a layer of a further kind is in physical contact with the outer surface of a die, then the layer of the further kind is in contact with the outer surface of the die.

[0181] Control power input

[0182] In one aspect of the invention, it is preferred that the electric power input to the device is controlled by controlling an electric power source connected to the device. For example, the current provided by the electric power source is reduced or increased. In another aspect of the invention, it is preferred that the electric power input to the device is controlled using at least one first type of layer. In another aspect of the invention, it is preferred that the electric power input to the device is controlled by controlling an electric power source connected to the device and using at least one first type of layer.

[0183] product

[0184] The product of the present invention is a ceramic body. The ceramic body preferably has a higher density than the plurality of particles. Preferably the body is a continuous object. Preferably the density of the body divided by the theoretical density is at least 0.9, preferably at least 0.95, more preferably at least 0.99.

[0185] Preferred ceramics are inorganic materials. Preferred ceramics are non-metallic. Some preferred ceramics are oxides, nitrides, carbides, or combinations thereof. Preferred ceramics are refractory materials.

[0186] Preferred oxide ceramics may be oxides of a single element, or mixed oxides of more than one element. Oxide ceramics may contain some nitride or carbide content or both. Oxide ceramics may be nitride-free or carbide-free or both. Preferred ceramic oxides may be stoichiometric or non-stoichiometric. Stoichiometric oxides preferably have integer ratios between the atomic numbers of their constituent elements. Oxide ceramics may contain two or more element groupings, each element in stoichiometric ratios to each other element of its own grouping, but in non-stoichiometric ratios to each element of other groupings.

[0187] Preferred nitride ceramics may be nitrides of a single element, or mixed nitrides of more than one element. Nitride ceramics may contain some oxide or carbide content or both. Nitride ceramics may be free of oxides or carbides or both. Preferred ceramic nitrides may be stoichiometric or non-stoichiometric. Stoichiometric nitrides preferably have integer ratios between the atomic numbers of their constituent elements. Nitride ceramics may contain two or more element groupings, each element being in stoichiometric ratios with each other element of its own grouping, but in non-stoichiometric ratios with each element of other groupings. Preferred carbide ceramics may be carbides of a single element, or mixed carbides of more than one element. Carbide ceramics may contain some oxide or nitride content or both. Carbide ceramics may be free of oxides or nitrides or both. Preferred ceramic carbides may be stoichiometric or non-stoichiometric. Stoichiometric carbides preferably have integer ratios between the atomic numbers of their constituent elements. Carbide ceramics may contain two or more groupings of elements, each element being in stoichiometric ratios with each other element of its own grouping, but in non-stoichiometric ratios with each element of the other groupings.

[0188] The preferred constituent element of the ceramic is yttrium. Based on the total weight of the ceramic, the ceramic may contain at least 20% by weight, preferably at least 30% by weight, more preferably at least 40% by weight, and most preferably at least 45% by weight of yttrium atoms. The yttrium content may be as high as 50% by weight, or even higher. Preferred yttrium-containing ceramics contain oxides. Preferred yttrium-containing ceramics are oxide ceramics, preferably mixed oxide ceramics, which contain atoms of one or more elements different from yttrium and oxygen. Mixed oxide ceramics are generally quantified according to the content of the simple oxides required to prepare them. Based on the total weight of the ceramic, preferred yttrium-containing mixed oxide ceramics contain at least 20% by weight, preferably at least 30% by weight, more preferably at least 40% by weight, and most preferably at least 45% by weight of yttrium oxide. The yttrium content may be as high as 50% by weight, or even higher.

[0189] In addition to oxygen, nitrogen and carbon, some preferred elements present in the ceramic are one or more elements selected from the list consisting of yttrium, zirconium, aluminum, titanium, silicon, boron, phosphorus and beryllium. These elements can be components of oxides, nitrides, carbides or combinations thereof.

[0190] Oxygen-containing ceramics are usually quantified according to the amount of simple oxides required to prepare them. Some preferred oxide components are silicon dioxide, boron oxide, beryllium oxide, yttrium oxide, aluminum oxide, zirconium oxide, titanium oxide, silicon dioxide, quartz, calcium oxide, cerium oxide, nickel oxide, copper oxide, strontium oxide, scandium oxide, samarium oxide, hafnium oxide, vanadium oxide, niobium oxide, tungsten oxide, manganese oxide, tantalum oxide, terbium oxide, europium oxide, neodymium oxide, yttrium aluminate oxide, zirconium aluminate oxide, lanthanum oxide, lutetium oxide, and erbium oxide.

[0191] Some preferred mixed oxides are one or more selected from the group consisting of zirconium silicate oxide, hafnium aluminate oxide, hafnium silicate oxide, titanium silicate oxide, lanthanum silicate oxide, lanthanum aluminate oxide (LAO), yttrium silicate oxide, titanium silicate oxide, tantalum silicate oxide, oxynitride, barium titanate, lead titanate and lead zirconate titanate.

[0192] Nitrogen-containing ceramics are usually quantified according to the amount of simple nitride required to make them. Some preferred nitride components are one or more selected from the group consisting of silicon nitride, titanium nitride, yttrium nitride, aluminum nitride, boron nitride, beryllium nitride, and tungsten nitride.

[0193] Carbon-containing ceramics are usually quantified according to the amount of simple carbide required to make them. Some preferred carbide components are silicon carbide, tungsten carbide, chromium carbide, vanadium carbide, niobium carbide, molybdenum carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide, and boron carbide.

[0194] The ceramic may contain one or more borides. Some preferred boride components of the ceramic are one or more selected from the group consisting of: molybdenum boride, chromium boride, hafnium boride, zirconium boride, tantalum boride and titanium boride or titanium diboride. Some preferred ceramic substances are one or more selected from the group consisting of: sapphire, aluminum oxide, yttrium aluminum monoclinic (YAM) (preferably Y4Al2O9), yttrium aluminum garnet (YAG) (preferably Y3Al5O 12 ), yttrium aluminum perovskite (YAP) (preferably YAlO3), cordierite, mullite, magnesium aluminum spinel, zirconia, erbium aluminum garnet (EAG), yttrium oxynitride, silicon oxynitride and forsterite.

[0195] Starting Materials

[0196] According to the present invention, a plurality of particles in a sintering chamber can be transformed into a body by applying pressure and electric current. The particles can have the same chemical composition as the product. The preferred chemical composition of the product is also the preferred chemical composition of the particles.

[0197] The preferred size of the particles is in the range of 0.1 μm to 20 μm. The preferred average size of the particles is in the range of 0.3 μm to 7 μm, more preferably in the range of 0.5 μm to 5 μm.

[0198] Method conditions

[0199] The sintering of the particles is carried out under pressure. A pressure of at least 1 MPa, preferably at least 5 MPa, more preferably at least 10 MPa is applied to the particles in the sintering chamber. The applied pressure may be in the range of 15 MPa to 30 MPa. Pressures up to about 80 MPa or even higher may be applied.

[0200] The sintering of the particles is carried out with the application of an electric current. Preferably, a current of at least 5 kA, more preferably at least 10 kA, more preferably at least 50 kA is applied across the sintering chamber. Currents up to 100 kA or even greater may be applied.

[0201] The method is preferably carried out in a non-oxidizing atmosphere. The method can be carried out in a vacuum, with the gas pressure around the device being less than 10 mPa, preferably less than 5 mPa, more preferably less than 1 mPa. The method can be carried out in an inert atmosphere, preferably argon.

[0202] In one aspect of the present invention, it is preferred that during the method for preparing a ceramic body according to the present invention, a potential difference is applied between the first punch inner surface and the second punch inner surface of the device according to the present invention, wherein the potential difference is in the range of 5V to 10V, more preferably in the range of 5V to 7V, and further preferably in the range of 6V to 6.5V.

[0203] Technology Application

[0204] Ceramic bodies can be used in various technical applications. Some specific applications are one or more selected from the list consisting of: plasma etcher, plasma processing chamber (etching or deposition process), wear plates for load bearings or mill linings for grinding mills.

[0205] Electric power source

[0206] The electrical power source is preferably adapted and arranged to generate Joule heating in the plurality of particles. The electrical power source may be an alternating current, a pulsed direct current or a continuous direct current. Continuous direct current is preferred.

[0207] In one aspect of the invention, it is preferred that the electrical power source is a rectified DC power source. A rectified DC power source should preferably be understood to mean an electrical power source adapted and arranged to convert an alternating current into a direct current. An example of a rectified DC power source is an electrical power source adapted and arranged to perform partial wave rectification, full wave rectification (e.g., a bridge rectifier), or both. Preferred rectified DC power sources include thyristors, silicon controlled rectifiers, or both.

[0208] The electrical power source is preferably adapted and arranged to provide a current of at least 5 kA, more preferably at least 10 kA, even more preferably at least 50 kA, further preferably at least 60 kA, and even further preferably at least 100 kA.

[0209] picture

[0210] The invention will now be further elucidated with the aid of the following drawings. The drawings are not drawn to scale.

[0211] Figure 1A is a cross-sectional side view of a first embodiment of a device according to the present invention.

[0212] Figure 1B is a cross-sectional side view of a second embodiment of a device according to the present invention.

[0213] Figure 1C is a cross-sectional side view of a third embodiment of a device according to the present invention.

[0214] Figure 1D is a schematic diagram of how to measure the thickness of another type of layer.

[0215] Figure 1E is a cross-sectional side view of a fourth embodiment of a device according to the present invention.

[0216] Figure 2 yes Figure 1A Cross-sectional side view of a first embodiment of the apparatus with the chamber loaded and ready for sintering.

[0217] Figure 3 The steps of a method for preparing a ceramic body are shown.

[0218] Figure 4 A cutaway cross section of a sintering chamber is shown.

[0219] 5a and 5b illustrate the core test employed herein.

[0220] Figure 6 Core test success as a function of temperature gradient is shown.

[0221] Figure 7 The electrical power density required to produce a ceramic body of sufficiently high quality is shown. BRIEF DESCRIPTION OF THE DRAWINGS

[0222] Figure 1A 1 is a cross-sectional side view of a first embodiment of a device 100 according to the present invention. The device comprises a first punch 003 having a first punch inner surface 004 and a second punch 008 having a second punch inner surface 007. Punches 003 and 008 are made of solid graphite. Punch inner surfaces 004 and 007 are also made of graphite. The first punch 003 is positioned above the second punch 008. The first punch 003 is oriented so that the first punch inner surface 004 is horizontal and downward. The first punch 003 can be moved in a vertical direction by a first push device 001 connected via a first piston 002. The second punch 008 is oriented so that the second punch inner surface 007 is horizontal and upward. The second punch 008 can be moved in a vertical direction by a second push device 010 connected via a second piston 009. The first punch inner surface 004 and the second punch inner surface 007 can therefore move toward each other along the direction of the compression axis 011.

[0223] The device has a die head 006 shaped as a hollow graphite cylinder with an inner surface 005. The device has an electric power source 012, which is suitable and arranged to supply DC current and is connected to a first punch 003 and a second punch 008. The sintering chamber 013 of the present invention is formed as a cavity defined by the first punch inner surface 004 from above, the second punch inner surface 007 from below, and the inner surface 005 to the side. In this case, the punch inner surfaces 004 and 007 are both circular, and the inner surface 005 is cylindrical, and therefore the sintering chamber 013 is cylindrical.

[0224] Figure 1B is a cross-sectional side view of a second embodiment of a device 100 according to the present invention. Figure 1B The device has Figure 1A The same features as the device in. However, Figure 1B The device in has the following additional features. A first layer 014 of a first kind having a thickness 016 is arranged between the punch 003 and the piston 002. The first layer 014 of the first kind is in electrical, thermal and physical contact with a first outer surface 020 of the punch 003. Similarly, a second layer 015 of a first kind having a thickness 017 is arranged between the punch 008 and the piston 009. Another layer 015 of the first kind is in electrical, thermal and physical contact with a second outer surface 021 of the punch 008. The layers 014 and 015 of the first kind are made of a composite carbon material. By changing the thickness 016 or the thickness 017 or both, the electrical power input to the punches 003 and 008 can be controlled within a selected range.

[0225] Figure 1Cis a cross-sectional side view of a third embodiment of a device 100 according to the present invention. Figure 1C The device has Figure 1A The same features as the device in. However, Figure 1C The device in has the following additional features. A further layer 018 made of felt surrounds the outer surface 019 of the die 006. The outer surface 019 is the surface of the die 006 that does not define the sintering chamber 013. The further layer 018 can be uniform around the outer surface 019. However, it is preferred that the thickness of the further layer 018 varies around the outer surface 019. Figure 1C As shown, the thickness of additional kind of layer 018 measured parallel to compression axis 011 (ie, at the top and bottom of die 006 ) is less than the thickness measured perpendicular to compression axis 011 (ie, at the sides of die 006 ).

[0226] Figure 1D It is a schematic diagram of how to measure the thickness of another type of layer 018. Figure 1D yes Figure 1C 006 and an enlarged view of the die 006 and the additional layer 018 in FIG. The thickness of the additional layer parallel to the compression 011 is measured as indicated by arrow 022. The thickness of the additional layer perpendicular to the compression 011 is measured as indicated by arrow 023.

[0227] Figure 1E is a cross-sectional side view of a fourth embodiment of a device 100 according to the present invention. Figure 1E The device 100 is Figure 1B and Figure 1C The device 100 shown in FIG. 1 is a combination of the second embodiment and the third embodiment. Specifically, Figure 1E The fourth embodiment of the device 100 in has layers 014 and 015 of the first type and a layer 018 of the further type.

[0228] Figure 2 yes Figure 1AA cross-sectional side view of a first embodiment of the device 100, wherein the sintering chamber 013 is loaded and prepared for sintering. The sintering chamber 013 is defined by the first punch inner surface 004 from above, the second punch inner surface 007 from below and the inner surface 005 of the die 006 to the side. The sintering chamber 013 therefore has a cylindrical shape. The sintering chamber 013 is filled with a plurality of particles for sintering. A plurality of particles can be rammed to compact them after being introduced into the sintering chamber. Then the punch inner surface (004, 007) is moved inwardly to abut against the compacted particle disk. For sintering, the punch inner surface (004, 007) moves inwardly along the compression axis 011, as shown by the arrow. The punch inner surface (004, 007) applies force to the particles, thereby generating pressure in the chamber. Current is applied across the sintering chamber 013 from an electric power source 012 (between the first punch inner surface 004 and the second punch inner surface 007). When the sintering process is complete, the ceramic body is allowed to cool.

[0229] Figure 2 The method described in also applies to Figure 1B 013. The second embodiment of the device 100 shown in FIG. 100. When the device 100 is according to the second embodiment, the electrical power input (and therefore the electrical power density) to the sintering chamber is controlled by the first type of layers 014 and 015. The presence of the first type of layers 014 and 015 makes it possible to generate a temperature gradient between the center of the sintering chamber 013 and the inner surface 005 of the die 006. The center of the sintering chamber 013 is defined as an imaginary line coinciding with the compression axis 011 passing through the sintering chamber 013. In addition, the temperature at the center of the sintering chamber 013 is lower than the temperature at the inner surface 005 of the die 006.

[0230] Figure 2 The method described in also applies to Figure 1C 005. The presence of the additional type of layer 018 makes it possible to generate a temperature gradient between the center of the sintering chamber 013 and the inner surface 005 of the die 006. In addition, the temperature at the center of the sintering chamber 013 is lower than the temperature at the inner surface 005 of the die 006. Different thicknesses of the additional type of layer allow different cooling rates of the ceramic body.

[0231] Figure 2 The method described in also applies to Figure 1E A fourth embodiment of the device 100 described in . The device having a combination of at least one layer of a first kind and a layer of another kind allows controlling the temperature gradient between the center of the sintering chamber 013 and the inner surface 005 of the die 006. In addition, the temperature at the center of the sintering chamber 013 is lower than the temperature at the inner surface 005 of the die 006.

[0232] Figure 3The steps of a method 200 for preparing a ceramic body are shown. In a first step a.201, a plurality of particles are provided. The particle size d 50 It can be, for example, 3 μm. An exemplary material for the particles is yttrium aluminum garnet (YAG). In a second step b.202, an apparatus as described in the present disclosure is provided. The sintering chamber of the apparatus can, for example, have a diameter of 500 mm. In a third step c.203, a plurality of particles are introduced into the sintering chamber of the apparatus. Optionally, a graphite layer is introduced at the inner surface of the die before the particles. Optionally, a graphite layer at the inner surface of the second punch can also be introduced before the particles. A plurality of particles can be rammed to compact the particles into a cylinder. Optionally, the graphite layer for the inner surface of the first punch can be located at the top of the particles before being below the inner surface of the first punch. In a fourth step d.204, a pressure of, for example, 50 MPa is applied to the sintering chamber, and an electric current is passed through the chamber to convert the particles into a product ceramic body.

[0233] Figure 4 A cutaway cross section 300 of the sintering chamber 013 is shown. The cut is vertical, along the diameter of the sintering chamber 013, through the compression axis 011, to show the sintering chamber 013 from the side. The die 006 is a hollow cylinder with a wall thickness 302. The die thickness 302, the layer thickness 301 and the diameter 303 of the sintering chamber 013 are each measured in a radial direction perpendicular to the compression axis 011. Figure 4 It is also shown how to measure the temperature gradient in the sintering chamber 013. The temperature gradient is measured in a radial direction perpendicular to the compression axis 011. In addition, the temperature gradient is measured between the compression axis 011 (through the center of the sintering chamber 013) and the inner surface 005 of the die 006, as shown by arrow 301.

[0234] Figures 5a and 5b illustrate the core test 400 employed herein. Figure 5a shows a perspective view before the start of the test. A coring tool 401 is positioned above a first flat surface 402 of a ceramic sample 406 in flat form. In this case, the ceramic sample 406 in flat form is in the form of a cylindrical disk. The tool 401 is oriented along an axis perpendicular to the first flat surface 402. Arrow 408 shows the direction in which the tool 401 travels along the axis toward the ceramic sample 406 in flat form. Once in contact with the ceramic sample 406 in flat form, the coring tool 401 moves in a circular motion within a coring area 407, the diameter of which is greater than the diameter of the tip 409 of the coring tool 401. The circular motion is parallel to the first flat surface 402 and results in the removal of a cylindrical area from the ceramic sample 406 in flat form. In addition, the geometric center 405 of the first flat surface 402 is also the geometric center 405 of the coring area 407. Figure 5b shows a cross-sectional view from the side during the core test. The tool 401 has been advanced a distance 403 into a flat form ceramic sample 406 having a sample thickness 404. FIG5 b shows that the coring tool 401 has removed a cylindrical section 410 from the flat form ceramic sample 406. The distance 403 is determined between the first flat surface 402 and the end of the tool 401. The test ends when a crack is first observed in the flat form ceramic sample 406. The success level is determined as the ratio of the distance 403 of the core to the total thickness of the flat form ceramic sample 404 at the end of the test, expressed as a percentage.

[0235] Test Method

[0236] Core Test

[0237] The sample ceramic of the flat form with the first flat surface and the thickness perpendicular to the first flat surface obtained in the embodiment is cored to determine whether there is excessive internal stress. The coring tool 401 is a 10mm diamond coring tool, for example, commercially available from Schott Diamantwerkzeuge GmbH, Stadtoldendorf, Germany. The tool is used in a commercially available CNC machine to cut a core in the part to be tested. The hole formed in the part by cutting the core is 56mm to 60mm, with a nominal diameter of 58mm. The core is cut by passing the tool 401 on the surface of the part in a spiral mode to drill a hole in the part. Suitable CNC machines that can be used for this test are available from, for example, DMG Mori Company Limited, Los Angeles, California, USA, such as its Ultrasonic 60eVo linear model. Another supplier of suitable CNC machines is Fair Friend Ent. Co. Ltd., Taiwan, such as Feeler HV-1650 model. The test ends when the core extends all the way through the sample ceramic or when the sample ceramic is observed to fracture, whichever occurs first. The success score is given as a percentage of the thickness of the core cut in the sample to be tested. A success rating of 100% indicates low internal stress (if any); a success rating above 75% but below 100% indicates low internal stress; a success rating between 25% and 75% indicates corresponding to medium stress; and a success rating below 25% indicates high internal stress.

[0238] Particle size and average particle size

[0239] The particle size and average particle size of the ceramic particles are determined using a laser scattering particle size distribution analyzer model LA-960 obtained from Horiba Scientific, Piscataway, New Jersey in the United States.

[0240] thickness

[0241] The thickness of the first type of layer and the additional type of layer are measured using calipers.

[0242] temperature

[0243] The temperature in the sintering chamber was measured using an exposed thermocouple located at the center of the sintering chamber. Suitable thermocouples are commercially available from Nanmac Corporation (USA).

[0244] The temperature at the inner surface of the die is measured using a spot pyrometer. Suitable pyrometers are available from Fluke Process Instruments (USA).

[0245] Resistivity and resistance

[0246] The resistivity of the layer of the first kind is measured according to standard ASTM B193-20.

[0247] Thermal properties of the layer

[0248] Thermal conductivity is measured according to standard ASTM E1461-13 (2022).

[0249] Thermal emissivity is measured according to standard ASTM C835-06 (2020).

[0250] The specific heat capacity is measured according to standard ASTM E1269-11 (2018).

[0251] Cooling rate of ceramic body

[0252] Cooling rate R C Use the following formula to calculate:

[0253] R C =(T S –20℃) / t C ,

[0254] Where T S is the temperature of the ceramic body measured at the completion of the sintering process, and t C Is a ceramic body from T S Time required to cool to 20°C.

[0255] Density and theoretical density

[0256] The density of the ceramic body is measured according to standard ASTM B962-17. The theoretical density is calculated from X-ray diffraction (XRD) data. The unit cell parameters a, b and c are obtained from the XRD data. Using the unit cell parameters, the unit cell volume is calculated. Based on the crystal structure of the material, the number of molecular units present in each unit cell is determined. The molecular weight of the ceramic body is known because its chemical structure is known. Using the aforementioned data, the theoretical density is calculated as follows:

[0257] Theoretical density = (molecular weight x number of molecules per unit cell) / (volume of unit cell x Avogardo number)

[0258] Average grain size

[0259] The average grain size of the ceramic body is measured according to standard ASTM E112-13 (2021).

[0260] Example

[0261] The working of the invention will now be further elucidated with the aid of specific embodiments. The invention is not limited by the features of the embodiments, which are intended to provide specific concrete implementations of the invention.

[0262] In the following examples,

[0263] ΔT = T2 – T1,

[0264] Where T2 is the temperature measured at the center of the sintering chamber, and T1 is the temperature measured at the inner surface of the die.

[0265] In the examples that follow, a ceramic body is considered to be of sufficiently high quality if the core test success is at least 90% and if the average grain size is below 5 μm.

[0266] Example A

[0267] according to Figure 1E The schematic diagram shown provides an apparatus. The die head has a height of 1 m, and the punches each have a circular punch inner surface with a diameter of 650 mm. The sintering chamber accordingly has a cylindrical shape with a cross-sectional diameter of 650 mm. The punch is moved by a piston. In addition, a first type of layer in the form of a carbon fiber composite plate is located between the punch and the piston, as Figure 1B In addition, the outer surface of the die is surrounded by a felt layer (another type of layer), similar to Figure 1C The felt layer has a non-uniform thickness, as Figure 1C The thickness of the felt layer measured parallel to the compression axis is 10 mm, while the thickness of the felt layer measured perpendicular to the compression axis is 20 mm.

[0268] The particle size d 50 Commercially available yttrium oxide and aluminum oxide powders of 3 μm were mixed together and 5 kg of the mixture was introduced into the sintering chamber, spread to an approximate horizontal height and compacted with a force of about 40 tons to a compaction height of 20 mm. After sintering, the powder mixture formed yttrium aluminum garnet (YAG). Next, a mixture of commercially available powders was introduced into the sintering chamber in an amount of 27 kg to produce zirconium oxide toughened alumina (ZTA) when sintered and spread to an approximately uniform height of about 100 mm. Finally, a mixture of powders for forming YAG and ZTA was introduced into the sintering chamber in an amount of 7 kg and spread to an approximately uniform height of about 30 mm.

[0269] The punch moves inward to reach Figure 2The position shown. A force is applied to the powder in the sintering chamber by the first punch and the second punch to reach a sintering chamber pressure of about 15 MPa. The current supplied via the punches is passed through the sintering chamber for a total of 9 to 10 hours. The product is a cylindrical ceramic disc in flat form with a diameter of about 650 mm and a thickness of about 26 mm.

[0270] This example was repeated using different values ​​of the temperature difference ΔT measured between the center of the sintering chamber and the inner surface of the die as shown in Table 1 below. The density ratio in Table 1 is the value of the bulk density of the ceramic body divided by the theoretical density of the ceramic body. The average grain size refers to the average size of the crystallites or crystals of the ceramic body.

[0271] Although the above-described embodiments are three-layer cylindrical ceramic disks, the methods disclosed herein are also applicable to such disks in single-layer and double-layer forms.

[0272] Example B

[0273] Example B was carried out in the same manner as Example A, but the circular diameter of the inner surface of the punch was 100 mm. The results are also shown in Table 1 below.

[0274] Table 1

[0275]

[0276] When considering the results in Table 1 for the inner surface of a punch with a circular diameter of 100 mm, there is no indication that the temperature gradient ΔT should be within a specific range in order to produce a ceramic body of sufficiently high quality with a diameter of 650 mm.

[0277] Figure 6 The core test success is shown as a function of the temperature gradient ΔT for Example A. Figure 6 "Low" corresponds to a core test success rate between 0% and 70%, "Medium" corresponds to a core test success rate between >70% and 90%, and "High" corresponds to a core test success rate greater than 90%. Figure 6 A "high" core test success rate is obtained when ΔT is in the range of 20°C to 125°C.

[0278] Example C

[0279] according to Figure 1B The schematic diagram shown provides an apparatus. The height of the die head is 1 m, and the punches each have a circular punch inner surface with a diameter of 650 mm. The sintering chamber accordingly has a cylindrical shape with a cross-sectional diameter of 650 mm. The punch is moved by a piston. In addition, a layer of the carbon fiber composite plate is located between the punch and the piston, as shown in FIG. Figure 1B described.

[0280] The particle size d 50 Commercially available yttrium oxide and aluminum oxide powders of 3 μm were mixed together and 5 kg of the mixture was introduced into the sintering chamber, spread to an approximate horizontal height and compacted with a force of about 40 tons to a compaction height of 20 mm. After sintering, the powder mixture formed yttrium aluminum garnet (YAG). Next, a mixture of commercially available powders was introduced into the sintering chamber in an amount of 27 kg to produce zirconium oxide toughened alumina (ZTA) when sintered and spread to an approximately uniform height of about 100 mm. Finally, a mixture of powders for forming YAG and ZTA was introduced into the sintering chamber in an amount of 7 kg and spread to an approximately uniform height of about 30 mm.

[0281] The punch moves inward to reach Figure 2 The position shown. A force is applied to the powder in the sintering chamber by the first punch and the second punch to reach a sintering chamber pressure of about 15 MPa. 40 kA to 70 kA supplied via the punches is passed through the sintering chamber for a total of 9 to 10 hours. The product is a cylindrical ceramic disc in flat form with a diameter of about 650 mm and a thickness of about 26 mm.

[0282] The example was repeated using different values ​​of electrical power density as shown in Table 1 below. Electrical power density is defined as the electrical power input P calculated using the following formula:

[0283] P=I*V / A,

[0284] Where I is the current supplied to the sintering chamber, V is the potential difference between the inner surface of the first punch and the inner surface of the second punch, and A is the surface area of ​​the inner surface of the first punch (the surface areas of the inner surface of the first punch and the inner surface of the second punch are the same). The electric power density is changed by changing the thickness of the carbon fiber composite plate.

[0285] The density ratio in Table 2 is the value of the bulk density of the ceramic body divided by the theoretical density of the ceramic body. The average grain size refers to the average size of the crystallites or crystals of the ceramic body.

[0286] Although the above-described embodiments are three-layer cylindrical ceramic disks, the methods disclosed herein are also applicable to such disks in single-layer and double-layer forms.

[0287] Example D

[0288] Example D was carried out in the same manner as Example C, but the circular diameter of the inner surface of the punch was 100 mm. The results are also shown in Table 2 below.

[0289] Table 2

[0290]

[0291] Notes to Table 2:

[0292] * The grain size has a very large standard deviation. In addition, there is also extreme grain growth at the edges of the produced ceramic bodies.

[0293] **Grain size has a very large standard deviation.

[0294] When considering the results in Table 2 for a punch inner surface with a circular diameter of 100 mm, there is no indication that the electrical power density should be changed in order to produce a ceramic body of sufficiently high quality with a diameter of 650 mm.

[0295] Similar results to those in Table 2 are also shown in Figure 7 middle. Figure 7 The electric power density required to produce a ceramic body of sufficiently high quality is shown. For a ceramic body with a diameter of 100 mm, a very large range of electric power densities (approximately 1.8 W / mm 2 To about 3.5W / mm 2 For a ceramic body with a diameter of 500 mm, the power density range is (about 1.2 W / mm 2 To about 0.6W / mm 2 ) is narrower than the range for the 100mm ceramic body. The range for the 500mm part also falls outside the range for the 100mm part. For the 650mm diameter ceramic body, the electrical power density range is the narrowest (about 0.6W / mm 2 To about 0.4W / mm 2 ). The range of 650mm parts also falls outside the range of 100mm and 500mm parts.

[0296] Example E

[0297] according to Figure 1C The schematic diagram shown provides an apparatus. The height of the die is 1 m, and the punches each have a circular punch inner surface with a diameter of 650 mm. The sintering chamber accordingly has a cylindrical shape with a cross-sectional diameter of 650 mm. In addition, the outer surface of the die is surrounded by a felt layer (another kind of layer), similar to Figure 1C As described in.

[0298] The particle size d 50Commercially available yttrium oxide and aluminum oxide powders of 3 μm were mixed together and 5 kg of the mixture was introduced into the sintering chamber, spread to an approximate horizontal height and compacted with a force of about 40 tons to a compaction height of 20 mm. After sintering, the powder mixture formed yttrium aluminum garnet (YAG). Next, a mixture of commercially available powders was introduced into the sintering chamber in an amount of 27 kg to produce zirconium oxide toughened alumina (ZTA) when sintered and spread to an approximately uniform height of about 100 mm. Finally, a mixture of powders for forming YAG and ZTA was introduced into the sintering chamber in an amount of 7 kg and spread to an approximately uniform height of about 30 mm.

[0299] The punch moves inward to reach Figure 2 The position shown. A force is applied to the powder in the sintering chamber by the first punch and the second punch to reach a sintering chamber pressure of about 15 MPa. 40 kA to 70 kA supplied via the punches is passed through the sintering chamber for a total of 9 to 10 hours. The product is a cylindrical ceramic disc in flat form with a diameter of about 650 mm and a thickness of about 26 mm.

[0300] The felt layer has a non-uniform thickness, e.g. Figure 1C As described. The thickness of the felt layer measured parallel to the compression axis is 0.5 times the thickness of the felt measured perpendicular to the compression axis. This embodiment is repeated using felt layers of different thicknesses. The thicknesses measured perpendicular to the compression axis for different embodiments are shown in Table 3. It should be noted that in Example E1, there is no felt layer on any part of the outer surface of the die. The density ratio in Table 3 is the value of the bulk density of the ceramic body divided by the theoretical density of the ceramic body. The average grain size refers to the average size of the crystallites or crystals of the ceramic body.

[0301] Although the above-described embodiments are three-layer cylindrical ceramic disks, the methods disclosed herein are also applicable to such disks in single-layer and double-layer forms.

[0302] Example F

[0303] Example F was carried out in the same manner as Example E, but the circular diameter of the inner surface of the punch was 100 mm. The results are also shown below in Table 3. Note that in Example F1, there was no felt layer present on any part of the outer surface of the die.

[0304] Table 3

[0305]

[0306]

[0307] When considering the results in Table 3 for a punch inner surface having a circular diameter of 100 mm, there is no indication that the presence of a felt layer is required in order to produce a sufficiently high quality ceramic body of 650 mm in diameter. Table 3 also shows that when a felt layer is present for a punch inner surface having a circular diameter of 100 mm, there is no indication that the thickness of the felt layer should be varied in order to produce a sufficiently high quality ceramic body of 650 mm in diameter.

[0308] Other embodiments

[0309] The foregoing examples A to F were repeated, but the circular diameter of the inner surface of the punch was 400 mm and 500 mm, respectively. For ceramic bodies with diameters of 400 mm and 500 mm, the influence of ΔT, electrical power density and felt sleeve thickness became important in order to obtain a sufficiently high quality ceramic body. Using the values ​​of ΔT and the thickness of the felt sleeve given in Tables 1 and 3, respectively, similar results were obtained for the 400 mm and 500 mm ceramic bodies as for the 650 mm ceramic body. However, a higher power density was required for the 500 mm ceramic body, and an even higher power density was required for the 400 mm ceramic body, compared to the 650 mm ceramic body.

[0310] Reference List

[0311] 100 The device according to the present invention

[0312] 001 First Propulsion Device

[0313] 002 First Piston

[0314] 003 First Punch

[0315] 004 Inner surface of the first punch

[0316] 005 Inner surface of die head

[0317] 006 Die Head

[0318] 007 Inner surface of the second punch

[0319] 008 Second Punch

[0320] 009 Second Piston

[0321] 010 Second propulsion device

[0322] 011 Compression axis

[0323] 012 Electric power source

[0324] 013 Sintering Chamber

[0325] 014, 015 The first type of layer

[0326] 016, 017 Thickness of the first type of layer

[0327] 018 Another type of layer

[0328] 019 The outer surface of the die head

[0329] 020 First punch outer surface

[0330] 021 Second punch outer surface 022 Thickness of another type of layer parallel to the compression axis 023 Thickness of another type of layer perpendicular to the compression axis 200 Preparation method of ceramic body 201 Step a.

[0331] 202 Step b.

[0332] 203 Step c.

[0333] 204 Step d.

[0334] 300 Cross section of a sintering chamber

[0335] 301 Measuring the distance of temperature gradient

[0336] 302 Die wall thickness

[0337] 303 Sintering chamber diameter

[0338] 400-core test setup

[0339] 401 Coring Tools

[0340] 402 first flat surface

[0341] 403 Drilling depth

[0342] 404 Sample thickness

[0343] 405 Geometric Center

[0344] 406 Ceramic samples in flat form

[0345] 407 Coring Area

[0346] 408 perpendicular to the direction of motion of the flat ceramic sample

[0347] 409 Tip of coring tool

[0348] 410 Cylindrical section removed from a flat ceramic sample

Claims

1. A device having a sintering chamber (013), the sintering chamber (013) being defined by the following device components: i. an inner surface (004) of a first punch (003); ii. the second punch inner surface (007) of the second punch (008); as well as iii. the inner surface (005) of the die (006); in: The punch (003, 008) is adapted and arranged to apply a pressure of at least 1 MPa to the target in the sintering chamber (013) along a compression axis (011); The first punch (003) and the second punch (008) are connected to an electric power source (012); The first punch and the second punch (003, 008) comprise at least 50 wt% carbon based on the total weight of the punch (003, 008); The sintering chamber (013) has a cross-sectional width W perpendicular to the compression axis (011) of at least 300 mm; Wherein the device is adapted and arranged to control the temperature in the sintering chamber.

2. The device according to claim 1, further comprising a first layer (014) of the first kind in physical contact with the surface of the first punch (003), wherein the first layer of the first kind has a resistivity in the range of 1010 μΩ·m to 26010 μΩ·m.

3. The device of claim 2, wherein the first layer of the first type has a power consumption of 0.1 W·m -1 ·K -1 Up to 55W·m -1 ·K -1 The thermal conductivity is within the range of . 4 . The device of claim 2 , wherein the first layer of the first species comprises carbon, silicon, or a combination thereof.

5. The device according to any one of the preceding claims, wherein the device further comprises a layer of another kind arranged at least partially around the outer surface (019) of the die, and wherein the layer of another kind has a thermal conductivity of 0.2 W·m 2 at 1400° C. -1 ·K -1 Up to 0.65W·m -1 ·K -1 The thermal conductivity is within the range of .

6. The device according to claim 5, wherein the additional type of layer has at least one or all of the following properties: a. At 0.005 g·cm -3 Up to 0.22 g·cm -3 Density within the range of b. Measured at 1400°C at 1.40 J·g -1 ℃ -1 Up to 1.95 J·g -1 ℃ -1 The average specific heat capacity in the range of c. Thermal emissivity in the range of 0.7 and 0.

99.

7. The device according to any one of claims 5 to 6, wherein the additional type of layer comprises carbon, ceramic, molybdenum or a combination of at least two thereof.

8. The device according to any one of claims 5 to 7, wherein the further kind of layer has a thickness in the range of 1 mm to 45 mm.

9. A method for preparing a ceramic body, the method comprising the steps of: a. Providing multiple particles; b. Providing a device comprising a sintering chamber (013) defined by a die (006); c. introducing the particles into the sintering chamber; d. applying a pressure P in the range of 1 MPa to 80 MPa to the plurality of particles in the sintering chamber to obtain the ceramic body, in The temperature in the sintering chamber is controlled during the preparation of the ceramic body so that the temperature at the center of the sintering chamber is lower than the temperature at the inner surface (006) of the die head. 10 . The method of claim 9 , wherein a temperature gradient between the center of the sintering chamber and the inner surface of the die head is in a range of 0.005° C. / mm to 0.55° C. / mm.

11. The method according to any one of claims 9 to 10, wherein the sintering chamber is defined by at least one punch having a punch surface, and wherein the electrical power density measured at the punch surface is adjusted according to the diameter of the ceramic body being produced.

12. The method according to the preceding claim 11, wherein said electrical power density decreases when said diameter of said ceramic body to be prepared increases.

13. The method according to any one of claims 9 to 12, further comprising subjecting the prepared ceramic body to sintering in the sintering chamber at 100°C·hour -1 Up to 165℃·hour -1 range of cooling steps at a rate.

14. The method according to any one of claims 9 to 12, wherein the device is a device according to any one of claims 1 to 8.

15. A ceramic body obtainable by a method according to any one of claims 9 to 14.

16. The ceramic body according to claim 15, wherein at least one or all of the following are satisfied: a. The value of density divided by theoretical density is less than 1.0; b. The average grain size is less than 5μm; c. The standard deviation of the average grain size distribution is in the range of 1.8±2 μm to 2.2±2 μm.

17. An assembly comprising a ceramic body according to any one of claims 15 to 16.

18. Use of a temperature difference for producing a ceramic body having an extension of at least 300 mm by spark plasma sintering.

19. Use of a layer of the first type for producing a ceramic body having an extension of at least 300 mm by spark plasma sintering.

20. Use of a layer of another kind for producing a ceramic body having an extension of at least 300 mm by spark plasma sintering.

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