Sintering device with low surface roughness

Abstract

An apparatus having a sintering chamber (013), the sintering chamber (013) being delimited by: i. A first punch surface (004) of a first punch (003); ii. A second punch surface (007) of the second punch; and (008) iiii. An inner surface (005) of the die (006); wherein: the punch (003, 008) is adapted and arranged to apply a pressure of at least 1 MPa to a target in the sintering chamber (013) along the compression axis (011); the first punch (003) and the second punch (008) are connected to an electrical power source (012) adapted and arranged to provide a current of at least 10 kA; the first and second punches (003, 008) comprise at least 50% by weight of carbon, based on the total weight of the punches (003, 008); the sintering chamber (013) has a cross-sectional width W of at least 300 mm perpendicular to the compression axis (011); wherein the die has a surface portion chi having an area of at least 5 cm2, where the surface portion chi is located on the inner surface of the die and where the surface portion chi has an average surface roughness (Sa) in the range of 1 [mu] m to 8 [mu] m.

Description

[0001] Description Technical Field

[0002] The present invention generally relates to sintering under pressure and using an electric current, commonly known as spark plasma sintering (SPS). Specific aspects of the present invention relate to the use of a low surface roughness of a sintering device, a sintering method, a ceramic body product, a component including a ceramic body, and a die head of the device in a sintering method. Background Art

[0003] Sintering methods provide a way to form a body from particles by applying heat and pressure. In one method commonly known 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. The existing literature has focused on small-scale systems, thus providing access to components with a physical extension of up to about 150 mm. Eugene A. Olevsky et al. evaluated the problems 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)). A number of potential challenges and complications associated with large-scale systems have been identified. Summary of the Invention

[0004] An object of the present invention is to provide an improved method for preparing a ceramic body. A specific object of the present invention is to provide an improved method for preparing a ceramic body with an increased size.

[0005] An object of the present invention is to provide an improved method for preparing a ceramic body with a reduced energy requirement.

[0006] An object of the present invention is to provide an improved method for preparing a ceramic body with a reduced reject rate.

[0007] An object of the present invention is to provide an improved method for preparing a ceramic body with a reduced fracture sensitivity.

[0008] An object of the present invention is to provide an improved method for preparing a ceramic body with a reduced internal stress.

[0009] The object of the present invention is to provide an improved method for preparing a ceramic body with increased mechanical strength.

[0010] The object of the present invention is to provide an improved method for preparing a ceramic body with increased density.

[0011] The object of the present invention is to provide an improved method for preparing a ceramic body with increased density uniformity.

[0012] The object of the present invention is to provide an improved method for preparing a ceramic body with increased etch resistance.

[0013] The object of the present invention is to provide an improved method for preparing a ceramic body with reduced surface roughness.

[0014] The object of the present invention is to provide a device 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] The first embodiment of the present invention is a device having a sintering chamber, which is defined by the following device components:

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

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

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

[0020] Wherein:

[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, and 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 up to 50 MPa or even higher;

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

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

[0024] The sintering chamber has a cross-sectional width W perpendicular to the compression axis of at least 300 mm, preferably at least 500 mm, more preferably at least 700 mm. W can be up to 2000 mm or higher. It is preferably not more than 1500 mm, more preferably not more than 900 mm;

[0025] wherein the die head has a surface portion χ with an area of at least 5 cm 2 and the surface portion χ is located on the inner surface of the die head, and the average surface roughness (Sa) of the surface portion χ is in the range of 1 μm to 8 μm, preferably in the range of 2 μm to 7 μm, and preferably in the range of 3 μm to 6 μm, and further preferably in the range of 3 μm to 5 μm.

[0026] In one aspect of the first embodiment, it is preferred that the area of the surface portion x is at least 10 cm 2 , more preferably the area is at least 50 cm 2 , and further preferably the area is at least 100 cm 2 .

[0027] In a preferred embodiment of the device, the first punch has a surface portion α with an area of at least 5 cm 2 and the surface portion α has an average surface roughness (Sa) in the range of 1 μm to 8 μm, preferably in the range of 2 μm to 7 μm, and preferably in the range of 3 μm to 6 μm, and further preferably in the range of 3 μm to 5 μm. This preferred embodiment is the second embodiment of the present invention, and the second embodiment preferably depends on the first embodiment of the present invention.

[0028] In one aspect of the second embodiment, it is preferred that the area of the surface portion α is at least 10 cm 2 , more preferably the area is at least 50 cm 2 , and further preferably the area is at least 100 cm 2 . In one aspect of the second embodiment, it is preferred that the surface portion α at least partially overlaps with the die contact surface of the first punch.

[0029] In a preferred embodiment of the device, the surface portion α at least partially overlaps with the first punch surface. This preferred embodiment is the third embodiment of the present invention, and the third embodiment preferably depends on the second embodiment of the present invention.

[0030] In a preferred embodiment of the device, the surface portion α at least partially contacts the surface portion χ. This preferred embodiment is the fourth embodiment of the present invention, and the fourth embodiment preferably depends on the third embodiment of the present invention.

[0031] In a preferred embodiment of the device, the second punch has a surface portion β with an area of at least 5 cm 2 and the surface portion β has an average surface roughness (Sa) in the range of 1 μm to 8 μm, preferably in the range of 2 μm to 7 μm, and preferably in the range of 3 μm to 6 μm, and more preferably in the range of 3 μm to 5 μm. This preferred embodiment is the fifth embodiment of the present invention, and the fifth embodiment preferably depends on any one of the first to fourth embodiments of the present invention. In one aspect of the fifth embodiment, it is preferred that the area of the surface portion β is at least 10 cm 2 , more preferably at least 50 cm 2 , and further preferably at least 100 cm 2 . In one aspect of the fifth embodiment, it is preferred that the surface portion β at least partially overlaps with the die contact surface of the second punch. In one aspect of the fifth embodiment, it is preferred that the surface portion β at least partially contacts the surface portion χ.

[0032] In a preferred embodiment of the device, the surface portion β at least partially overlaps with the second punch surface. This preferred embodiment is the sixth embodiment of the present invention, and the sixth embodiment preferably depends on the fifth embodiment of the present invention.

[0033] In a preferred embodiment of the device, the surface portion χ has at least one or all of the following characteristics:

[0034] a. A maximum height (Sz) in the range of 20 μm to 100 μm, preferably in the range of 35 μm to 87 μm, and further preferably in the range of 44 μm to 62 μm;

[0035] b. A texture aspect ratio (Str) in the range of 0.01 to 0.75, preferably in the range of 0.1 to 0.65, and more preferably in the range of 0.41 to 0.5;

[0036] c. An arithmetic mean peak curvature (Spc) of at least 4000 mm -1 , preferably at least 7000 mm -1 , and further preferably at least 8000 mm -1 ;

[0037] d. An extended interface area ratio (Sdr) of at least 4, preferably at least 12, and further preferably at least 14.

[0038] This preferred embodiment is the seventh embodiment of the present invention, and the seventh embodiment preferably depends on any one of the first to sixth embodiments of the present invention. In one aspect of the seventh 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.

[0039] In a preferred embodiment of the device, the surface portion α and / or the surface portion β have at least one or all of the following characteristics:

[0040] a. A maximum height (Sz) in the range of 20 μm to 100 μm, preferably in the range of 35 μm to 87 μm, and more preferably in the range of 44 μm to 62 μm;

[0041] b. A texture aspect ratio (Str) in the range of 0.01 to 0.75, preferably in the range of 0.1 to 0.65, and more preferably in the range of 0.41 to 0.5;

[0042] c. An arithmetic mean peak curvature (Spc) of at least 4000 mm -1 preferably at least 7000 mm -1 and more preferably at least 8000 mm -1 ;

[0043] d. An extended interface area ratio (Sdr) of at least 4, preferably at least 12, and more preferably at least 14.

[0044] This preferred embodiment is the eighth embodiment of the present invention, and the eighth embodiment preferably depends on any one of the second to seventh embodiments of the present invention. In one aspect of the eighth 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.

[0045] In a preferred embodiment of the device, the two punches and the die are at least partially present in a vacuum chamber or a non-oxidizing atmosphere or both. This preferred embodiment is the ninth embodiment of the present invention, and the ninth embodiment preferably depends on any one of the first to eighth embodiments of the present invention.

[0046] In a preferred embodiment of the device, the electric power source is adapted and arranged to supply a DC voltage. This preferred embodiment is the tenth embodiment of the present invention, and the tenth embodiment preferably depends on any one of the first to ninth embodiments of the present invention.

[0047] In a preferred embodiment of the device, one or more of the following are satisfied:

[0048] a. Based on the total weight of carbon atoms in any chemical form and the total weight of the first punch, the first punch contains at least 99% by weight of carbon;

[0049] b. Based on the total weight of carbon atoms in any chemical form and the total weight of the second punch, the second punch contains at least 99% by weight of carbon;

[0050] c. Based on the total weight of carbon atoms in any chemical form and the total weight of the die, the die contains at least 50% by weight, more preferably at least 90% by weight, and even more preferably at least 99% by weight of carbon.

[0051] This preferred embodiment is the eleventh embodiment of the present invention, and the eleventh embodiment preferably depends on any one of the first to tenth embodiments of the present invention. In one aspect of the eleventh 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.

[0052] In a preferred embodiment of the device, the device includes one or more additional device components selected from the list consisting of:

[0053] a. A housing;

[0054] b. A vacuum device;

[0055] c. A hydraulic piston.

[0056] This preferred embodiment is the twelfth embodiment of the present invention, and the twelfth embodiment preferably depends on any one of the first to eleventh embodiments of the present invention. In one aspect of the twelfth 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.

[0057] The thirteenth embodiment of the present invention is a method for preparing a ceramic body, the method comprising the following steps:

[0058] a. Providing a plurality of particles;

[0059] b. Provide a device according to the present invention, preferably a device according to any one of the first to twelfth embodiments of the present invention;

[0060] c. Introduce the particles into the sintering chamber;

[0061] d. Apply a pressure P in the range of 1 MPa to 50 MPa and a current I in the range of 10 kA to 100 kA, more preferably in the range of 25 kA to 100 kA, and even more preferably in the range of 50 kA to 100 kA to the plurality of particles in the sintering chamber to obtain the ceramic body.

[0062] In a preferred embodiment of the method, based on the total mass of yttrium atoms and the total mass of the particles, 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. This preferred embodiment is the fourteenth embodiment of the present invention, and the fourteenth embodiment preferably depends on the thirteenth embodiment of the present invention.

[0063] The fifteenth embodiment of the present invention is a ceramic body obtainable by a method according to the present invention, preferably a method according to the thirteenth or fourteenth embodiment of the present invention.

[0064] In a preferred embodiment of the ceramic body, at least one or all of the following are satisfied for the ceramic body:

[0065] a. The value of the density divided by the theoretical density is less than 1.0;

[0066] b. An average grain size of less than 5 μm, preferably less than 4.5 μm, more preferably less than 4 μm, and further preferably 1 μm to 3 μm;

[0067] c. A standard deviation of the average grain size distribution in the range of 1.2 ± 2 mm to 2.8 ± 2 mm, preferably in the range of 1.6 ± 2 mm to 2.4 ± 2 mm, and more preferably in the range of 1.8 ± 2 mm to 2.2 ± 2 mm.

[0068] This preferred embodiment is the sixteenth embodiment of the present invention, and the sixteenth embodiment preferably depends on the fifteenth embodiment of the present invention. In one aspect of the sixteenth 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 one aspect of feature a. of the sixteenth embodiment, the value of the density divided by the theoretical density is preferably at least 0.9, more preferably at least 0.95, and further preferably at least 0.99.

[0069] The seventeenth embodiment of the present invention is a component comprising a ceramic body according to the present invention, preferably a ceramic body according to any one of the fifteenth to sixteenth embodiments of the present invention.

[0070] In a preferred embodiment of the component, the component is selected from the group consisting of:

[0071] a. A plasma etcher,

[0072] b. A plasma processing chamber (etching or deposition method),

[0073] c. A wear-resistant plate for carrying, and

[0074] d. A mill lining of a grinder.

[0075] This preferred embodiment is the eighteenth embodiment of the present invention, and the eighteenth embodiment preferably depends on the seventeenth embodiment of the present invention. In one aspect of the eighteenth 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.

[0076] The nineteenth embodiment of the present invention is the use of a punch for preparing a ceramic body having an extension of at least 300 mm by spark plasma sintering, wherein the punch has a surface portion with an area of at least 5 cm 2 and the average surface roughness (Sa) of the surface portion is in the range of 1 μm to 8 μm, preferably in the range of 2 μm to 7 μm, and preferably in the range of 3 μm to 6 μm, and further preferably in the range of 3 μm to 5 μm. In one aspect of the nineteenth embodiment, it is preferred that the area of the surface region is at least 10 cm 2 , more preferably an area of at least 50 cm 2 , and further preferably an area of at least 100 cm 2 . Detailed Description

[0077] The following abbreviations are used in the specification: AC (alternating current), DC (direct current).

[0078] Sintering

[0079] The present invention relates to a sintering method. The preferred sintering method produces a body from particles by applying pressure and heat. The heating is preferably carried out by applying an electric current.

[0080] Preferred sintering increases the density of a plurality of particles to produce a body. The body preferably has a higher density than the plurality of particles. Preferred 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.

[0081] Device

[0082] The apparatus of the present invention is adapted and arranged for sintering particles to produce a body. The apparatus includes at least a first punch, a second punch, and a die. The apparatus has a sintering chamber.

[0083] Sintering chamber

[0084] The apparatus of the present invention has a sintering chamber. The sintering chamber is preferably adapted and arranged to accommodate a plurality of particles. The sintering chamber is preferably defined by a first punch surface of the first punch, a second punch surface of the second punch, and an inner surface of the die. The sintering chamber may be defined only by the first punch surface, the second punch surface, and the inner surface, or may additionally be defined by one or more additional surfaces. The sintering chamber is preferably defined only by the first punch surface, the second punch surface, and the inner surface.

[0085] 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 rotational volume. The sintering chamber may be cylindrical.

[0086] Punch

[0087] The apparatus of the present invention has a first punch and a second punch. The first punch has a first punch surface defining the sintering chamber. The second punch has a second punch surface defining the sintering chamber. Preferably, one or both of the punch surfaces are substantially flat.

[0088] The punches are preferably adapted and arranged to apply a force to a target within the sintering chamber, preferably to generate an elevated pressure within the sintering chamber. The punches are preferably adapted and arranged to generate a pressure of at least 1 MPa, preferably at least 5 MPa, more preferably at least 10 MPa, and most preferably at least 15 MPa within the sintering chamber. The punches may be adapted and arranged to apply a pressure up to 50 MPa or even higher.

[0089] The first punch and the second punch are preferably vertically positioned above and below the sintering chamber, respectively. The first punch and the second punch are preferably adapted and arranged to move along a compression axis.

[0090] The punches are preferably electrically conductive. The punches are preferably adapted and arranged to provide a current of at least 10 kA, more preferably at least 50 kA, and most preferably at least 60 kA. The electrical power source may be adapted and arranged to provide a current up to 100 kA or even greater.

[0091] The punch is preferably made of a carbon material, most preferably made of graphite. The punch preferably contains at least 95% by weight of carbon, more preferably at least 99% by weight, still more preferably at least 99.5% by weight of carbon. The punch may include one or more selected from the following: layers and regions; made of materials other than carbon.

[0092] Die head

[0093] The device of the present invention has a die head. The die head has an inner surface that defines a sintering chamber.

[0094] In one embodiment, the die head is conductive. Preferably, the die head has anisotropic conductivity, preferably having a material orientation axis that is substantially aligned with the compression axis.

[0095] In one embodiment, the die head contains 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 head preferably contains 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, based on the total weight of the die head, the die head contains 50% by weight or more, more preferably 90% by weight or more, most preferably 95% by weight or more of Group 14 elements.

[0096] In one embodiment, based on the total weight of the die head, the die head contains at least 50% by weight, preferably 90% by weight or more, more preferably 95% by weight or more, most preferably 99% by weight or more of C. In one aspect of this embodiment, the die head additionally contains one or more other 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% by weight, more preferably at least 1% by weight, most preferably at least 2% by weight. In this embodiment, elements other than C, Si, Ge, Sn, and Pb are preferably present in a total content of not more than 1% by weight, more preferably not more than 0.5% by weight, most preferably not more than 0.1% by weight.

[0097] The die head is preferably made of a carbon material, most preferably made of graphite.

[0098] The die head can be a single piece or multiple pieces, preferably a single piece. Preferably, the die head is a single continuous body, more preferably a single cylinder. The die head preferably exists in 2 to 10 pieces, more preferably 2 to 5 pieces, still more preferably 2 to 3 pieces, most preferably 2 pieces.

[0099] 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 rotating volume. The sintering chamber may be hollow cylindrical.

[0100] Orientation

[0101] The device of the present 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.

[0102] Preferably, the first punch may move along the compression axis. Preferably, the second punch may move along the compression axis. Preferably, both punches may move along the compression axis.

[0103] In one embodiment, the compression axis is substantially vertical, preferably with the first punch positioned above the second punch. In one aspect of this embodiment, the first punch surface is preferably the lower surface of the first punch. In another aspect of this embodiment, the first punch surface is substantially horizontal. In another aspect of this embodiment, the second punch surface is preferably the upper surface of the second punch. In another aspect of this embodiment, the second punch surface is substantially horizontal.

[0104] Die head contact surface

[0105] The die head contact surface of the punch is defined as the surface of the punch that is adapted and arranged to make physical contact with the inner surface of the die head during the sintering process. Preferably, the die head contact surface is parallel to the compression axis.

[0106] Product

[0107] 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. The value of the density of the preferred body divided by the theoretical density is at least 0.9, preferably at least 0.95, more preferably at least 0.99.

[0108] Preferably, the ceramic is an inorganic material. Preferably, the ceramic is non-metallic. Some preferred ceramics are oxides, nitrides, carbides or combinations thereof. Preferably, the ceramic is a refractory material.

[0109] The preferred oxide ceramics can be oxides of a single element or mixed oxides of more than one element. The oxide ceramics can contain some nitride or carbide contents or both. The oxide ceramics can be free of nitrides or free of carbides or free of both. The preferred ceramic oxides can be stoichiometric or non-stoichiometric. Stoichiometric oxides preferably have an integer ratio between the atomic numbers of their constituent elements. The oxide ceramics can contain two or more groupings of elements, each element being in stoichiometric ratio with each other element within its own grouping but in non-stoichiometric ratio with each element in other groupings.

[0110] The preferred nitride ceramics can be nitrides of a single element or mixed nitrides of more than one element. The nitride ceramics can contain some oxide or carbide contents or both. The nitride ceramics can be free of oxides or free of carbides or free of both. The preferred ceramic nitrides can be stoichiometric or non-stoichiometric. Stoichiometric nitrides preferably have an integer ratio between the atomic numbers of their constituent elements. The nitride ceramics can contain two or more groupings of elements, each element being in stoichiometric ratio with each other element within its own grouping but in non-stoichiometric ratio with each element in other groupings.

[0111] The preferred carbide ceramics can be carbides of a single element or mixed carbides of more than one element. The carbide ceramics can contain some oxide or nitride contents or both. The carbide ceramics can be free of oxides or free of nitrides or free of both. The preferred ceramic carbides can be stoichiometric or non-stoichiometric. Stoichiometric carbides preferably have an integer ratio between the atomic numbers of their constituent elements. The carbide ceramics can contain two or more groupings of elements, each element being in stoichiometric ratio with each other element within its own grouping but in non-stoichiometric ratio with each element in other groupings.

[0112] A preferred constituent element of the ceramics is yttrium. Based on the total weight of the ceramics, the ceramics can contain at least 20 wt%, preferably at least 30 wt%, more preferably at least 40 wt%, and most preferably at least 45 wt% of yttrium atoms. The content of yttrium can be up to 50 wt% or even higher. The preferred yttrium-containing ceramics contain oxides. The preferred yttrium-containing ceramics are oxide ceramics, preferably mixed oxide ceramics, which contain atoms of one or more elements other than yttrium and oxygen. The mixed oxide ceramics are usually quantified based on the content of the simple oxides required to prepare them. Based on the total weight of the ceramics, the preferred yttrium-containing mixed oxide ceramics contain at least 20 wt%, preferably at least 30 wt%, more preferably at least 40 wt%, and most preferably at least 45 wt% of yttrium oxide. The content of yttrium oxide can be up to 50 wt% or even higher.

[0113] 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.

[0114] Oxygen-containing ceramics are typically quantified based on the content of the simple oxides required to prepare them. Some preferred oxide components are silica, boron oxide, beryllium oxide, yttrium oxide, aluminum oxide, zirconium oxide, titanium oxide, silica, 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.

[0115] 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, oxynitrides, barium titanate, lead titanate, and lead zirconate titanate.

[0116] Nitrogen-containing ceramics are typically quantified based on the content of the simple nitrides required to prepare 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.

[0117] Carbon-containing ceramics are typically quantified based on the content of the simple carbides required to prepare 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.

[0118] The ceramic can 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.

[0119] 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 aluminate spinel, zirconium oxide, erbium aluminum garnet (EAG), yttrium oxynitride, silicon oxynitride, and forsterite.

[0120] Starting material

[0121] According to the present invention, a plurality of particles in a sintering chamber can be converted into a body by applying pressure and an 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.

[0122] 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.

[0123] Method conditions

[0124] 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 can be in the range of 15 MPa to 30 MPa. Pressures up to about 80 MPa or even higher can be applied.

[0125] The sintering of the particles is carried out with an electric current applied. 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 can be applied.

[0126] The method is preferably carried out in a non-oxidizing atmosphere. The method can be carried out in a vacuum with a gas pressure around the device 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.

[0127] 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 a first punch surface and a second punch surface of a device according to the present invention, wherein the potential difference is in the range of 5 V to 10 V, more preferably in the range of 5 V to 7 V, and further preferably in the range of 6 V to 6.5 V.

[0128] Technical application

[0129] The ceramic body can be used in various technical applications. Some specific applications are one or more selected from the list consisting of: plasma etchers, plasma processing chambers (etching or deposition methods), wear-resistant plates for carriers or mill linings for grinders.

[0130] Electric power source

[0131] The electric power source is preferably adapted and arranged to generate Joule heating in the plurality of particles. The electric power source can be an alternating current, a pulsed direct current or a continuous direct current. A continuous direct current is preferred.

[0132] In one aspect of the present invention, preferably, the electric power source is a rectified DC power source. A rectified DC power source should preferably be understood to mean an electric power source adapted and arranged to convert an alternating current into a direct current. Examples of rectified DC power sources are electric power sources adapted and arranged to perform half-wave rectification, full-wave rectification (e.g., bridge rectifiers), or both. Preferred rectified DC power sources include thyristors, silicon-controlled rectifiers, or both.

[0133] The electric 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.

[0134] Figure

[0135] The present invention is further illustrated now with the aid of the following figures. These figures are not drawn to scale.

[0136] Figure 1A is a cross-sectional side view of a device according to the present invention.

[0137] Figure 1B is an enlarged view of the die and the punch.

[0138] Figure 2 A is a cross-sectional side view of the device of Figure 1, where the chamber is loaded and ready for sintering.

[0139] Figure 2 B is Figure 2 an enlarged view of the die and the punch of A.

[0140] Figure 3 shows the steps of a method for preparing a ceramic body.

[0141] Figure 4 shows a sectional cross-section of the sintering chamber.

[0142] Figures 5a and 5b show the core tests employed herein.

[0143] Figure 6 A and Figure 6 B show the possible orientations of the die and the punch before and during sintering. Description of the Drawings

[0144] Figure 1ACross-sectional side view of device 100 according to the present invention. The device includes a first punch 003 having a first punch surface 004 and a second punch 008 having a second punch surface 007. The punches 003 and 008 are made of solid graphite. The punch 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 such that the first punch surface 004 is horizontal and downward. The first punch 003 is movable in the vertical direction by a first actuating device 001 connected via a first piston 002. The second punch 008 is oriented such that the second punch surface 007 is horizontal and upward. The second punch 008 is movable in the vertical direction by a second actuating device 010 connected via a second piston 009. The first punch surface 004 and the second punch surface 007 can thus move towards each other along the direction of the compression axis 011.

[0145] The device has a die 006 shaped as a hollow graphite cylinder having an inner surface 005. The device has an electric power source 012, which is adapted and arranged to supply a DC current and is connected to the first punch 003 and the second punch 008. The sintering chamber of the present invention is formed as a cavity defined from above by the first punch surface 004, from below by the second punch surface 007, and to the sides by the inner surface 005. In this case, both the punch surfaces 004 and 007 are circular, and the inner surface 005 is cylindrical, and thus the sintering chamber is cylindrical.

[0146] Figure 1B is Figure 1A An enlarged view of the first punch and the second punch (003, 008) and the die 006. Figure 1B Shows that the first punch 003 has a die contact surface 014 (the first punch 003 is circular). Similarly, the second punch 008 also has a die contact surface 015 (the second punch 008 is also circular).

[0147] Figure 2 A is Figure 1ACross-sectional side view of apparatus 100, where sintering chamber 013 is loaded and ready for sintering. Sintering chamber 013 is defined from above by first punch surface 004, from below by second punch surface 007, and to the sides by inner surface 005 of die 006. Sintering chamber 013 thus has a cylindrical shape. Sintering chamber 013 is filled with a plurality of particles for sintering. The plurality of particles may be tamped after being introduced into the sintering chamber to compact them. Then the punch surfaces (004, 007) are moved inward against the compacted particle disk. For sintering, the punch surfaces (004, 007) are moved inward along compression axis 011, as indicated by the arrows. The punch surfaces (004, 007) apply a force to the particles, thereby generating pressure in the chamber. An electric current is applied from electric power source 012 across sintering chamber 013 (between first punch surface 004 and second punch surface 007).

[0148] Figure 2 B is Figure 2 An enlarged view of first punch and second punch (003, 008) and die 006. As can be seen, inner surface 005 of die 006 contacts die contact surfaces (014, 015) of first punch 003 and second punch 008 before and during the sintering method.

[0149] Figure 3 Shows the steps of ceramic body preparation method 200. In a first step a.201, a plurality of particles are provided. The particle size d 50 May 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 may have a diameter of, for example, 500 mm. In a third step c.203, a plurality of particles are introduced into the sintering chamber of the apparatus. The plurality of particles may be tamped to compact the particles into a cylinder. In a fourth step d.204, a pressure of, for example, 50 MPa is applied to the sintering chamber, and an electric current (e.g., 80 kA) is passed through the chamber to convert the particles into a product ceramic body.

[0150] Figure 4 Shows cross-sectional profile 300 of sintering chamber 013. The cut is vertical, along the diameter of sintering chamber 013, through compression axis 011, to show sintering chamber 013 from the side. Die 006 is a hollow cylinder with wall thickness 301. Die thickness 301 and diameter 302 of sintering chamber 013 are each measured in a radial direction perpendicular to compression axis 011.

[0151] Figures 5a and 5b illustrate the core test 400 employed herein. Figure 5a shows a perspective view before the test starts. The coring tool 401 is positioned above the first flat surface 402 of the ceramic sample 406 in flat form. In this case, the ceramic sample 406 in flat form is in the form of a cylindrical disc. 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 towards 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 the 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 region from the ceramic sample 406 in flat form. Further, 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 advanced a distance 403 into the ceramic sample 406 in flat form having a sample thickness 404. Figure 5b shows that the coring tool 401 has removed a cylindrical section 410 from the ceramic sample 406 in flat form. The distance 403 is determined between the first flat surface 402 and the end of the tool 401. The test ends when cracks in the ceramic sample 406 in flat form are first observed. The success level is determined as the ratio of the distance 403 of the core at the end of the test to the total thickness of the ceramic sample 404 in flat form, expressed as a percentage.

[0152] Figure 6 A and Figure 6 B illustrate the possible orientations of the die and the punch before and during sintering. Figure 6 A and Figure 6 B are Figure 2 magnified views of the die and the punch in A. Figure 6 A shows a preferred orientation in which the first punch and the second punch (003, 008) are arranged relative to the die 006 such that the distances 016 and 017 (indicated by arrows) vary from each other by less than 3%. This orientation can be achieved by selecting a die 006 having an inner surface 006 with a sufficiently large average surface roughness (Sa). In addition to selecting a sufficiently large average surface roughness for the inner surface 005, additional improvement in the orientation can be obtained by selecting a sufficiently large average surface roughness (Sa) for the die contact surface 014 of the first punch 003 and / or the die contact surface 015 of the second punch 008.

[0153] Figure 6 B shows the orientation when the inner surface 005 of the die 006 is too smooth (i.e., the value of the average surface roughness (Sa) is too small). As Figure 6 visible in B, the distance 016 is significantly greater than the distance 017.

[0154] Test method

[0155] Core test

[0156] The flat-form sample ceramic having a first flat surface and a 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 10 mm diamond coring tool, which can be commercially obtained from Schott Diamantwerkzeuge GmbH, Stadtoldendorf, Germany for example. This tool is used in a commercially available CNC machine to cut a core in the component to be tested. The hole formed in the component by cutting the core is 56 mm to 60 mm, with a nominal diameter of 58 mm. The core is cut by passing the tool 401 over the surface of the component in a spiral pattern to drill a hole in the component. Suitable CNC machines 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. in Taiwan, China, such as the 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 crack, 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 100% success rating indicates low internal stress (if any); a success rating higher than 75% but lower than 100% indicates low internal stress; a success rating of 25% to 75% indicates medium stress; and a success rating lower than 25% indicates high internal stress.

[0157] Surface roughness

[0158] The standard ISO 25178:2019 is used to measure the average surface roughness Sa (also known as the arithmetic mean height). The standard ISO 25178:2019 is also used to measure the maximum height (Sz), the texture aspect ratio (Str), the arithmetic mean peak curvature (Spc), and the extended interface area ratio (Sdr). To measure the surface roughness, a VK-X200 3D laser scanning microscope commercially available from Keyence Corporation (Japan) is used.

[0159] Particle size and average particle size

[0160] The particle size and average particle size of the ceramic particles were determined using a LA-960 type laser scattering particle size distribution analyzer from Horiba Scientific, Piscataway, New Jersey in the United States.

[0161] Current intensity, potential difference and resistance

[0162] The current intensity was measured using a MicroFUSION 400A silicon controlled rectifier (SCR) commercially available from Control Concepts Inc. (USA). The potential difference was measured using a DSCA31 analog voltage input signal conditioner commercially available from Dataforth Corporation (USA). The resistance was obtained by dividing the potential difference by the current intensity.

[0163] Density and theoretical density

[0164] The density of the ceramic body was measured according to standard ASTM B962-17. The theoretical density was calculated from X-ray diffraction (XRD) data. The unit cell parameters a, b, and c were obtained from the XRD data. Using the unit cell parameters, the unit cell volume was calculated. Based on the crystal structure of the material, the number of molecular units present in each unit cell was determined. The molecular weight of the ceramic body was known as its chemical structure was known. Using the foregoing data, the theoretical density was calculated as follows:

[0165] Theoretical density = (Molecular weight × Number of molecules per unit cell) / (Unit cell volume × Avogadro's number)

[0166] Average grain size

[0167] The average grain size of the ceramic body was measured according to standard ASTM E112-13 (2021).

[0168] Example

[0169] The operation of the present invention will now be further elucidated with the aid of specific examples. The present invention is not limited by the features of the examples, which are intended to provide specific specific implementations of the present invention.

[0170] Example A

[0171] An apparatus was provided according to the schematic diagram shown in FIG. 1. The height of the die head was 1 m, and each punch had a circular punch surface with a diameter of 650 mm. The sintering chamber accordingly had a cylindrical shape with a cross-sectional diameter of 650 mm.

[0172] The particle size d 50Commercially available yttrium oxide and alumina powders with a size of 3 μm were mixed together, and 5 kg of the mixture was introduced into the sintering chamber, spread to an approximately horizontal height, and compacted to a compaction height of 20 mm with a force of about 40 tons. After sintering, the powder mixture formed yttrium aluminum garnet (YAG). Next, a commercially available mixture of powders in an amount of 27 kg was introduced into the sintering chamber to produce zirconia toughened alumina (ZTA) during sintering, and spread to an approximately uniform height of about 100 mm. Finally, a mixture of powders used to form YAG and ZTA in an amount of 7 kg was introduced into the sintering chamber and spread to a substantially uniform height of about 30 mm.

[0173] The punch moves inward to reach the position as Figure 2 shown. Forces were applied to the powder in the sintering chamber by the first punch and the second punch to achieve a sintering chamber pressure of about 15 MPa. A current of 40 kA to 70 kA supplied via the punch was passed through the sintering chamber for a total of 9 to 10 hours. The product is a flat-form cylindrical ceramic disk with a diameter of about 650 mm and a thickness of about 26 mm.

[0174] As shown in Table 1, different values of the average surface roughness (Sa) of the inner surface of the die and the die contact surfaces of the first punch and the second punch were used to repeat the examples. The density ratio in Table 1 is the value obtained by dividing the bulk density of the ceramic body by the theoretical density of the ceramic body. The grain size refers to the size of the microcrystals or crystals of the ceramic body.

[0175] Although the above examples are three-layer cylindrical ceramic disks, the methods disclosed herein are also applicable to such disks in single-layer and double-layer forms.

[0176] Example B

[0177] Example B was carried out in the same manner as Example A, but the circular diameter of the punch surface was 100 mm. The results are also shown in Table 1 below. The resistance in Table 1 was measured on the die.

[0178] Table 1

[0179]

[0180] * The resistance values in Table 1 are given as a percentage increase from the value of 0.461 nΩ. The percentage increase is calculated as follows:

[0181] Increase % = |0.461 - experimental measured value| / 0.461 × 100%.

[0182] ** When the change in distances 016 and 017 (see Figure 6 A and Figure 6 B) is less than 3%, the orientation of the punch and the die is acceptable.

[0183] When the value of the surface roughness is too small, this results in very limited friction between the die and the punch. Consequently, the die and the punch become misaligned relative to each other, leading to serious problems in the production of the ceramic body. If the value of the surface roughness is too large, this results in increased electrical contact between the die and the punch, which in turn leads to the generation of additional heat in the sintering chamber during the production of the ceramic body. The subsequently obtained ceramic body has very poor quality.

[0184] When considering the results for the punch surface with a circular diameter of 100 mm in Table 1, there is no indication that the surface roughness should be limited to a specific range in order to produce a ceramic body with a diameter of 650 mm of sufficient high quality.

[0185] Additional example

[0186] The foregoing Examples A and B were repeated, but with circular diameters of the punch surface of 300 mm and 500 mm respectively. It was found that for 300 mm, the results were very similar to those for a diameter of 100 mm (Example B). The results for a diameter of 500 mm were very similar to the results of Example A.

[0187] Reference list

[0188] 100 Device according to the invention

[0189] 001 First actuating device

[0190] 002 First piston

[0191] 003 First punch

[0192] 004 First punch surface

[0193] 005 Inner surface of the die

[0194] 006 Die

[0195] 007 Second punch surface

[0196] 008 Second punch

[0197] 009 Second piston

[0198] 010 Second actuating device

[0199] 011 Compression axis

[0200] 012 Electric power source

[0201] 013 Sintering chamber

[0202] 014 Die contact surface of the first punch

[0203] 015 Die head contact surface of the second punch

[0204] 016 Distance

[0205] 017 Distance

[0206] 200 Preparation method of the ceramic body

[0207] 201 Step a.

[0208] 202 Step b.

[0209] 203 Step c.

[0210] 204 Step d.

[0211] 300 Cross-section of the sintering chamber

[0212] 301 Wall thickness of the die head

[0213] 302 Sintering chamber diameter

[0214] 400 Core test setup

[0215] 401 Core tool

[0216] 402 First flat surface

[0217] 403 Drilling depth

[0218] 404 Sample thickness

[0219] 405 Geometric center

[0220] 406 Ceramic sample in flat form

[0221] 407 Core area

[0222] 408 Direction of movement perpendicular to the flat-form ceramic sample

[0223] 409 Tip of the core tool

[0224] 410 Cylindrical section removed from the flat-form ceramic sample

Claims

1. An apparatus having a sintering chamber (013), the sintering chamber (013) being defined by the following apparatus components: i. The first punch surface (004) of the first punch (003); ii. The second punch surface (007) of the second punch (008); and iii. The inner surface (005) of the die head (006); Wherein: The punches (003, 008) are adapted and arranged to apply a pressure of at least 1 MPa to the target in the sintering chamber (013) along the compression axis (011); The first punch (003) and the second punch (008) are connected to an electric power source (012) adapted and arranged to provide a current of at least 10 kA; Based on the total weight of the punches (003, 008), the first punch and the second punch (003, 008) contain at least 50 wt% carbon; The sintering chamber (013) has a cross-sectional width W perpendicular to the compression axis (011) of at least 300 mm; wherein the die head has a surface portion χ with an area of at least 5 cm 2 which is located on the inner surface of the die head and wherein the average surface roughness (Sa) of the surface portion χ is in the range of 1 μm to 8 μm.

2. The device according to claim 1, wherein the first punch has a surface portion α with an area of at least 5 cm 2 and the surface portion α has an average surface roughness (Sa) in the range of 1 μm to 8 μm.

3. The apparatus according to claim 2, wherein the surface portion α at least partially overlaps with the first punch surface.

4. The apparatus according to claim 3, wherein the surface portion α at least partially contacts the surface portion χ.

5. The device according to any one of the preceding claims, wherein the second punch has a surface portion β with an area of at least 5 cm 2 and the surface portion β has an average surface roughness (Sa) in the range of 1 μm to 8 μm.

6. The apparatus according to claim 5, wherein the surface portion β at least partially overlaps with the second punch surface.

7. The apparatus according to any one of the preceding claims, wherein the apparatus comprises one or more additional apparatus components selected from the list consisting of: a. A housing; b. A vacuum device; c. A hydraulic piston.

8. A method for preparing a ceramic body, the method comprising the following steps: a. Providing a plurality of particles; b. Providing the apparatus according to any one of claims 1 to 7; c. Introducing the particles into the sintering chamber (013); d. Applying a pressure P in the range of 1 MPa to 50 MPa and a current I in the range of 10 kA to 100 kA to the plurality of particles in the sintering chamber to obtain the ceramic body.

9. The method according to claim 8, wherein based on the total mass of yttrium atoms and the total mass of the particles, the particles contain at least 30 wt% of yttrium in any chemical form.

10. A ceramic body obtainable by the method according to claim 8 or 9.

11. The ceramic body according to claim 10, wherein at least one or all of the following are satisfied: a. The value of density divided by the theoretical density is less than 1.0; b. The average grain size is less than 5 μm; c. The standard deviation of the average grain size distribution is in the range of 1.8 ± 2 μm to 2.2 ± 2 μm.

12. An assembly comprising the ceramic body according to claim 10 or 11.

13. The assembly according to claim 12, the assembly being selected from the group consisting of: a. A plasma etcher, b. A plasma processing chamber (etching or deposition method), c. A wear-resistant plate for carrying, and d. A mill liner of a grinder.

14. Use of a die for preparing a ceramic body having an extension of at least 300 mm by spark plasma sintering, wherein the die has a surface portion with an area of at least 5 cm 2 and the surface portion has an average surface roughness (Sa) in the range of 1 μm to 8 μm.

Images