Sintering apparatus having a die lining with increased thickness

Abstract

The present invention generally relates to sintering using an electric current under pressure, often referred to as spark plasma sintering (SPS). Particular aspects of the present invention are directed to a sintering apparatus, a sintering process, a ceramic body product, an assembly including a ceramic body, and the use of a graphite layer in the sintering process. The present invention is an apparatus having a sintering chamber (013), the sintering chamber being bounded by the following apparatus parts, namely i. a first punch face (004) of a first punch (003), and ii. a second punch face (007) of a second punch (008), and iii. an inner surface (005) of a die (006), and is the punches (003, 008) are adapted and configured to apply a pressure of at least 1 MPa along a compression axis (011) to a target within the sintering chamber, the first punch and the second punch are connected to a power supply (012) adapted and configured to supply a current of at least 5 kA, the first and second punches contain at least 50% by weight of carbon based on the total weight of the punches, the sintering chamber has a cross-sectional width W of at least 300 mm perpendicular to the compression axis, at least a part of the inner surface of the die has a layer δ of a carbon material C δ which has an average thickness D determined over the inner surface of the die δ and D δ is in the range of 1.1 mm to 8 mm, relating to the apparatus.

Description

Technical Field

[0001] The present invention generally relates to sintering using an electric current under pressure, often referred to as spark plasma sintering (SPS). Certain aspects of the present invention are directed to sintering apparatuses, sintering processes, ceramic body products, assemblies including ceramic bodies, and the use of graphite layers in sintering processes.

Background Art

[0002] Sintering methods provide a way to form a solid body from particles by applying heat and pressure. In one method, often referred to as spark plasma sintering (SPS), heating is achieved using an electric current. The current state-of-the-art spark plasma sintering method has been applied to various materials. Existing literature has focused on small-scale systems that enable the acquisition of parts with a physical range up to approximately 150 mm. The problem of preparing larger parts using SPS has been evaluated from a theoretical perspective by Eugene A. Olevsky et al. in "Fundamental Aspects of Spark Plasma Sintering: I. Experimental Analysis of Scalability" (J. Am. Ceram. Soc., 95[8], 2406 - 2413 (2012)) and "Fundamental Aspects of Spark Plasma Sintering: II. Experimental Analysis of Scalability" (J. Am. Ceram. Soc., 95[8], 2414 - 2422 (2012)). Several potential issues and complexities associated with large-scale systems have been identified.

Summary of the Invention

[0003] An object of the present invention is to provide an improved process for preparing a ceramic body. In particular, an object of the present invention is to provide an improved process for preparing a ceramic body with an increased size.

[0004] An object of the present invention is to provide an improved process for preparing a ceramic body with relaxed energy requirements.

[0005] An object of the present invention is to provide an improved process for preparing a ceramic body with reduced waste rate.

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

[0007] An object of the present invention is to provide an improved process for preparing a ceramic body with reduced internal stress.

[0008] An object of the present invention is to provide an improved process for preparing a ceramic body with enhanced mechanical strength.

[0009] An object of the present invention is to provide an improved process for preparing a ceramic body with increased density.

[0010] An object of the present invention is to provide an improved process for preparing a ceramic body with enhanced density uniformity.

[0011] An object of the present invention is to provide an improved process for preparing a ceramic body with enhanced etching resistance.

[0012] An object of the present invention is to provide an improved process for preparing a ceramic body with reduced surface roughness.

[0013] An object of the present invention is to provide an apparatus for implementing the improved process described above.

[0014] Any embodiment of the present invention contributes to at least partial achievement of at least one of the above-described objects.

[0015] The first embodiment of the present invention is an apparatus having a sintering chamber, the sintering chamber being the following apparatus parts, namely, i. the first punch surface of the first punch, and ii. the second punch surface of the second punch, and iii. the inner surface of the die, bounded by, The punches are adapted and configured 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 along the compression axis to a target within the sintering chamber. The punches may be adapted and configured to apply up to 80 MPa, or even more; The first punch and the second punch are connected to a power source adapted and configured to supply a current of at least 5 kA, preferably at least 10 kA, more preferably at least 50 kA, and most preferably at least 60 kA. The power source may be adapted and configured to supply a current up to 100 kA, or even more, The first and second punches contain at least 50 wt%, preferably at least 90 wt%, more preferably at least 95 wt%, and most preferably at least 99 wt% carbon, based on the total weight of the punches, 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 reach a size of 2000 mm or more. Preferably this is 1500 mm or less, more preferably 900 mm or less, A layer δ of carbon material C is present on at least a part of the inner surface of the die δ and this layer δ has an average thickness D determined over the inner surface of the die δ and D δ is in the range of 1.1 mm to 8 mm, preferably in the range of 1.3 mm to 4 mm, more preferably in the range of 1.5 mm to 3 mm, still more preferably in the range of 1.9 mm to 2.5 mm.

[0016] In a preferred embodiment of the device, the width W is at least 500 mm, and the thickness D δ is at least 1.5 mm, preferably at least 1.8 mm, more preferably at least 1.93 mm. This preferred embodiment is the second embodiment of the present invention, which preferably depends on the first embodiment of the present invention.

[0017] In another preferred embodiment of the device, the width W is less than 500 mm, and the thickness D δ is at most 1.8 mm, preferably at most 1.6 mm, more preferably at most 1.3 mm. This preferred embodiment is the third embodiment of the present invention, which preferably depends on the first or second embodiment of the present invention.

[0018] In a preferred embodiment of the device, the layer δ has a standard deviation D of thickness in the range of 0.01 mm to 0.08 mm, preferably in the range of 0.02 mm to 0.06 mm, more preferably in the range of 0.03 mm to 0.05 mm, determined across the inner surface of the die. δ This preferred embodiment is the fourth embodiment of the present invention, which preferably depends on any one of the first to third embodiments of the present invention.

[0019] In a preferred embodiment of the device, the layer δ is composed of two or more laminated sub-layers, preferably 2 to 10 layers, or 2 to 8 layers, or 2 to 6 layers. This preferred embodiment is the fifth embodiment of the present invention, which preferably depends on any one of the first to fourth embodiments of the present invention.

[0020] In a preferred embodiment of the device, the chamber has a diameter D C and the ratio D C of the diameter D δ to the average thickness D of the layer C :D δ is in the range of 100:1 to 250:1, preferably in the range of 120:1 to 230:1, more preferably in the range of 130:1 to 210:1. This preferred embodiment is the sixth embodiment of the present invention, which preferably depends on any one of the first to fifth embodiments of the present invention.

[0021] In a preferred embodiment of the device, both the punch (003, 008) and the die are at least partially present within a vacuum chamber or in a non-oxidizing atmosphere or both. This preferred embodiment is the seventh embodiment of the present invention, which preferably depends on any of the first to sixth embodiments of the present invention.

[0022] In a preferred embodiment of the present device, the power supply is adapted and configured to supply a DC voltage. This preferred embodiment is the eighth embodiment of the present invention, which preferably depends on any of the first to seventh embodiments of the present invention.

[0023] In a preferred embodiment of the device, one or both of the following are satisfied: a. A layer ε of carbon material C having an average thickness preferably in the range of 1.1 mm to 8 mm is present on at least a part of the first punch surface ε thereof. b. A layer θ of carbon material C having an average thickness preferably in the range of 1.1 mm to 8 mm is present on at least a part of the second punch surface θ thereof.

[0024] This preferred embodiment is the ninth embodiment of the present invention, which preferably depends on any of the first to eighth embodiments of the present invention. In aspects 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.

[0025] In a preferred embodiment of the device, one or more of the following are satisfied: a. The first punch is at least 99% by weight carbon based on the total weight of carbon atoms in any chemical form and the total weight of the first punch. b. The second punch is at least 99% by weight carbon based on the total weight of carbon atoms in any chemical form and the total weight of the second punch. c. The die is at least 99% by weight carbon based on the total weight of carbon atoms in any chemical form and the total weight of the die. d. Layer δ is at least 99% by weight carbon, based on the total weight of carbon atoms in any chemical form and the total weight of layer δ.

[0026] This preferred embodiment is the tenth embodiment of the present invention, which preferably depends on any one of the first to ninth embodiments of the present invention. In aspects of the tenth 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.

[0027] In a preferred embodiment of the device, the die is made of carbon material Cγ, and one or more of the following are satisfied: a. C δ [[ID=[]3]]and C γ have different anisotropy values, b. C δ and C γ have different specific conductivities determined in a direction parallel to the compression axis, c. C δ and C γ have different specific conductivities determined in a direction perpendicular to the inner surface, d. C δ and C γ have different specific thermal expansion rates determined in a direction parallel to the compression axis, e. C δ and C γ have different specific thermal expansion rates determined in a direction perpendicular to the inner surface, f. The first carbon material and the second carbon material have different ash contents determined by ASTM C - 561.

[0028] This preferred embodiment is the eleventh embodiment of the present invention, which preferably depends on any one of the first to tenth embodiments of the present invention. In terms of the aspects 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 + e + f, a + b + c + d, a + b + c + e, a + b + c + f, a + b + d + e, a + b + d + f, a + b + e + f, a + c + d + e, a + c + d + f, a + c + e + f, a + d + e + f, b + c + d + e, b + c + d + f, b + c + e + f, b + d + e + f, c + d + e + f, a + b + c + d + e, a + b + c + d + f, a + b + c + e + f, a + b + d + e + f, a + c + d + e + f, b + c + d + e + f, a + b + c + d + e + f.

[0029] The twelfth embodiment of the present invention is a process for the preparation of a ceramic body, a. providing a plurality of particles; b. providing a device according to the present invention; c. introducing the particles into the sintering chamber of the device; d. applying a pressure P in the range of 1 MPa to 80 MPa and 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 still more preferably in the range of 60 kA to 100 kA to obtain a ceramic body.

[0030] The device provided in this twelfth embodiment is preferably a device according to any one of the first to eleventh embodiments of the present invention.

[0031] In a preferred embodiment of the process, the particles contain at least 30% by weight, preferably at least 40% by weight, 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 13th embodiment of the present invention, which preferably depends on the 12th embodiment of the present invention.

[0032] In a preferred embodiment of the process, the average thickness D after step d. δ divided by the thickness D before step a. δ has a value that is preferably at least 0.8, more preferably at least 0.9, even more preferably at least 0.95. This preferred embodiment is the 14th embodiment of the present invention, which preferably depends on the 12th or 13th embodiment of the present invention.

[0033] The 15th embodiment of the present invention is a ceramic body that can be obtained by the process according to the present invention. The process is preferably according to any one of the 12th to 14th embodiments.

[0034] In a preferred embodiment of the ceramic body, for the ceramic body, at least one or all of the following are satisfied: a. The value of the density divided by the theoretical density that is less than 1.0, b. An average particle size of less than 5 μm, preferably less than 4.5 μm, more preferably less than 4 μm, even more preferably 1 μm to 3 μm, c. A standard deviation of the average particle size distribution in the range of 1.2 μm ± 2 μm to 2.8 ± 2 μm, preferably in the range of 1.6 ± 2 μm to 2.4 ± 2 μm, more preferably in the range of 1.8 ± 2 μm to 2.2 ± 2 μm.

[0035] This preferred embodiment is the 16th embodiment of the present invention, which preferably depends on the 15th embodiment of the present invention. In terms of the aspects of the 16th 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 terms of the aspect of feature a. of the 16th embodiment, the value of the density divided by the theoretical density is preferably at least 0.9, more preferably at least 0.95, and still more preferably at least 0.99.

[0036] The 17th embodiment of the present invention is an assembly comprising a ceramic body according to the present invention, preferably according to either the 15th or 16th embodiment.

[0037] In a preferred embodiment of the assembly, the assembly is selected from the group consisting of: a. A plasma etcher, b. A plasma processing chamber (etching or deposition process), c. A wear plate for a shaft, d. A mill liner of a grinding mill.

[0038] This preferred embodiment is the 18th embodiment of the present invention, which preferably depends on the 17th embodiment of the present invention.

[0039] The 19th embodiment of the present invention is the use of a graphite layer having a thickness in the range of 1.1 mm to 8 mm, preferably in the range of 1.3 mm to 4 mm, more preferably in the range of 1.5 mm to 3 mm, and still more preferably in the range of 1.8 mm to 2.5 mm, for preparing a ceramic body having a spread of at least 300 mm by spark plasma sintering.

Mode for Carrying Out the Invention

[0040] Sintering The present invention is directed to a sintering process. A preferred sintering process produces a solid body from particles by applying pressure and heat. The heating is preferably by applying an electric current.

[0041] Preferred sintering increases the density of a plurality of particles to produce a solid body. The solid body preferably has a higher density than the plurality of particles.

[0042] Preferred sintering produces a product having a density of at least 95%, preferably at least 99%, more preferably at least 99.9% of its theoretical density.

[0043] Device The device of the present invention is adapted and configured to sinter particles to produce a solid body. The device comprises at least a first punch, a second punch, and a die. The device has a sintering chamber.

[0044] Sintering chamber The device of the present invention has a sintering chamber. The sintering chamber is preferably adapted and configured to accommodate a plurality of particles. The sintering chamber is preferably bounded by a first punch face of the first punch, a second punch face of the second punch, and an inner surface of the die. The sintering chamber may be bounded only by the first punch face, the second punch face, and the inner surface, or may be additionally bounded by one or more further surfaces. The sintering chamber is preferably bounded only by the first punch face, the second punch face, and the inner surface of the die.

[0045] 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 solid of revolution. The sintering chamber may be cylindrical.

[0046] Punch The device of the present invention has a first punch and a second punch. The first punch has a first punch face that bounds the sintering chamber. The second punch has a second punch face that bounds the sintering chamber. Preferably, one or both of the punch faces are substantially flat.

[0047] The punch is preferably adapted and configured to apply force to a target within the sintering chamber, preferably to cause a pressure increase within the sintering chamber. The punch is preferably adapted and configured to cause 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 punch may be adapted and configured to apply up to 80 MPa, or even more.

[0048] The first and second punches are preferably located above and below the sintering chamber in the vertical direction, respectively. The first and second punches are preferably adapted and configured to move along the compression axis.

[0049] The punch preferably has conductivity. The punch is preferably adapted and configured to provide a current of at least 5 kA, preferably at least 10 kA, more preferably at least 50 kA, and most preferably at least 60 kA passing through the sintering chamber. The power supply may be adapted and configured to supply a current up to 100 kA, or even more.

[0050] The punch is preferably made of a carbon material, most preferably graphite. The punch preferably contains at least 95 wt% carbon, more preferably at least 99 wt%, and even more preferably at least 99.5 wt% carbon. The punch may include one or more selected from layers and regions of materials other than carbon.

[0051] Die The device of the present invention has a die. The die has an inner surface that bounds the sintering chamber.

[0052] In one embodiment, the die has conductivity. The die preferably has anisotropic conductivity and preferably has a material arrangement direction axis substantially aligned with the compression axis.

[0053] In one embodiment, the die contains one or more elements selected from Group 14 of the periodic table. Group 14 elements may also be referred to as Group IVA elements or Group 4A elements. The die 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, and most preferably selected from C and Si. C is the most preferred Group 14 element. In one aspect of this embodiment, the die contains 50 wt% or more, more preferably 90 wt% or more, and most preferably 95 wt% or more of the Group 14 element based on the total weight of the die.

[0054] In one embodiment, the die contains at least 50 wt%, preferably 90 wt% or more, more preferably 95 wt% or more, and most preferably 99 wt% or more of C based on the total weight of the die. In one aspect of this embodiment, the die additionally contains one or more further Group 14 elements preferably selected from Si, Ge, Sn, and Pb, more preferably selected from Si, Ge, and Sn, even more preferably selected from Si and Ge, and most preferably Si. The further Group 14 element preferably exists with a total content of at least 0.1 wt%, more preferably at least 1 wt%, and most preferably at least 2 wt%. Elements other than C, Si, Ge, Sn, and Pb in this embodiment preferably exist with a total content of 1 wt% or less, more preferably 0.5 wt% or less, and most preferably 0.1 wt% or less.

[0055] The die may be a single piece or multiple pieces, but is preferably a single piece. The die is preferably a single continuum, and more preferably a single cylinder. Preferably, there are 2 to 10 die pieces, more preferably 2 to 5 die pieces, even more preferably 2 to 3 die pieces, and most preferably 2 die pieces.

[0056] The die may have one or more planes of symmetry or one or more axes of symmetry or both. The sintering chamber may be in the form of a rotating body. The sintering chamber may be a hollow cylinder.

[0057] The die is preferably made of a carbon material, and most preferably made of graphite.

[0058] Arrangement direction The device of the present invention has a compression axis. The device is preferably adapted and configured to apply a force to the sintering chamber along the direction of the compression axis.

[0059] 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.

[0060] In one embodiment, the compression axis is substantially vertical, and preferably the first punch is located above the second punch. In an 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.

[0061] The sintering chamber is preferably adapted and configured to accommodate a plurality of particles.

[0062] Layer In the device of the present invention, a layer of carbon material exists on at least a part of the inner surface of the die.

[0063] In one embodiment, the layer is present on 20% or more, preferably 50% or more, more preferably 90% or more, and most preferably 95% or more of the inner surface of the die, based on the total area of the inner surface of the die. Most preferably, the layer is present on substantially the entire inner surface of the die.

[0064] In one embodiment, the layer lines the inner surface of the die, and preferably lines substantially the entire surface of the die.

[0065] In one embodiment, a first gap exists between the inner surface of the die and the first punch, and the layer is preferably present in at least a part of the gap, more preferably substantially all of the gap.

[0066] In one embodiment, a second gap exists between the inner surface of the die and the second punch, and the layer is preferably present in at least a part of the gap, more preferably substantially all of the gap.

[0067] In one embodiment, the apparatus comprises a further layer.

[0068] The layer may be a single layer or may have at least two laminated sub-layers. The layer preferably has at least two laminated sub-layers, preferably between 2 and 20 laminated sub-layers. It is preferred that the layer or any sub-layer can exist over a part of the inner circumference of the die, or substantially over the entire inner circumference of the die, or over the entire inner circumference of the die and at least partially overlapping itself.

[0069] The layer is preferably near the inner surface of the die, more preferably in physical contact with the inner surface of the die. The layer may be a component not integrally connected to the inner surface of the die. This can be the case especially before the sintering process. The layer may be integrally connected to the inner surface of the die. This can be the case especially after the sintering process.

[0070] The thickness of the layer is determined as an average over the entire inner surface of the die.

[0071] The layer may be a graphite foil. The graphite foil preferably has a plurality of 2D flakes. The graphite foil is preferably configured to form a roll.

[0072] The layer preferably has an ash content of less than 1 wt%, more preferably less than 0.5 wt%, even more preferably less than 0.4 wt%.

[0073] Product The product of the present invention is a ceramic body. The ceramic body preferably has a higher density than a plurality of particles. A preferred solid body is an object without a break. A preferred solid body has a density value divided by the theoretical density of at least 0.9, preferably at least 0.95, more preferably at least 0.99.

[0074] 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.

[0075] Preferred oxide ceramics can be oxides of a single element or mixed oxides of two or more elements. The oxide ceramic may contain a certain amount of nitride content or carbide content, or both. The oxide ceramic may contain no nitride, no carbide, or neither. Preferred ceramic oxides may be stoichiometric or non-stoichiometric. Stoichiometric oxides preferably have an integer ratio between the numbers of atoms of their constituent elements. The oxide ceramic may contain elements grouped into two or more groups, and each element is stoichiometric with respect to each other element in its own grouping, but non-stoichiometric with respect to each member of other groupings.

[0076] Preferred nitride ceramics can be nitrides of a single element or mixed nitrides of two or more elements. The nitride ceramic may contain a certain amount of oxide content or carbide content, or both. The nitride ceramic may contain no oxide, no carbide, or neither. Preferred ceramic nitrides may be stoichiometric or non-stoichiometric. Stoichiometric nitrides preferably have an integer ratio between the numbers of atoms of their constituent elements. The nitride ceramic may contain elements grouped into two or more groups, and each element is stoichiometric with respect to each other element in its own grouping, but non-stoichiometric with respect to each member of other groupings.

[0077] Preferred carbide ceramics can be single-element carbides or mixed carbides of two or more elements. The carbide ceramics may contain a certain amount of oxide content or nitride content, or both. The carbide ceramics may not contain oxides, may not contain nitrides, or may not contain both. Preferred ceramic carbides may be stoichiometric or non-stoichiometric. Stoichiometric carbides preferably have an integer ratio between the numbers of atoms of their constituent elements. The carbide ceramics may contain elements grouped into two or more groups, and each element is stoichiometric with respect to each other element in its own grouping, but non-stoichiometric with respect to each member of other groupings.

[0078] A preferred constituent element of the ceramic is yttrium. The ceramic may 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 based on the total weight of the ceramic. The content of yttrium may be up to 50 wt% or even higher. Preferred yttrium-containing ceramics contain oxides. Preferred yttrium-containing ceramics are oxide ceramics, preferably mixed oxide ceramics containing atoms of one or more elements different from yttrium and oxygen. Mixed oxide ceramics are often quantified with respect to the content of simple oxides considered necessary to prepare them. 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 based on the total weight of the ceramic. The content of yttrium oxide may be up to 50 wt% or even higher.

[0079] In addition to oxygen, nitrogen, and carbon, some preferred elements present in the ceramic are one or more 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.

[0080] Oxygen-containing ceramics are often quantified relative to the content of simple oxides considered necessary to prepare them. Some preferred oxide components are silica, boria, 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 aluminum garnet, zirconium aluminum garnet, lanthanum oxide, lutetium oxide, and erbium oxide.

[0081] Some preferred mixed oxides are one or more selected from the group consisting of zirconium silicate oxide, hafnium aluminate, 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.

[0082] Nitrogen-containing ceramics are often quantified relative to the content of simple nitrides considered necessary 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.

[0083] Carbon-containing ceramics are often quantified relative to the content of simple carbides considered necessary to prepare them. Some preferred carbide constituents are silicon carbide, tungsten carbide, chromium carbide, vanadium carbide, niobium carbide, molybdenum carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide, and boron carbide.

[0084] The ceramic may contain one or more borides. Some preferred boride constituents 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.

[0085] Some preferred ceramic species are sapphire, alumina, yttrium aluminium monoclinic (YAM), preferably Y4Al2O9, yttrium aluminium garnet (YAG), preferably Y3Al5O 12 , yttrium aluminum perovskite (YAP), preferably YAlO3, cordierite, mullite, magnesium aluminate spinel, zirconia, erbium aluminum garnet (EAG), yttrium oxynitride, silicon oxynitride, and forsterite, one or more selected from the group consisting of.

[0086] Starting material According to the present invention, a plurality of particles in a sintering chamber can be converted into a solid body by applying pressure and current.

[0087] The particles can have the same chemical composition as the product. The preferred chemical composition of the product is also the preferred chemical composition for the particles.

[0088] The preferred size of the particles is 0.1 μm to 20 μm.

[0089] Process conditions The sintering of the particles proceeds 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 can be applied.

[0090] The sintering of the particles proceeds by applying 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 so as to pass through the sintering chamber. Currents up to 100 kA or even higher can be applied.

[0091] The process is preferably carried out in a non-oxidizing atmosphere. The process may be carried out in a vacuum, and the gas pressure around the apparatus is less than 10 mPa, preferably less than 5 mPa, more preferably less than 1 mPa. The process can be carried out in an inert atmosphere, preferably argon.

[0092] Technical applications The ceramic body is used in various technical applications. Some specific applications are one or more selected from the list consisting of a plasma etcher, a plasma processing chamber (etching or deposition process), a wear plate for a shaft, or a mill liner of a grinding mill.

[0093] Power supply The power supply is preferably adapted and configured to provide Joule heating to a plurality of particles. The power supply may be alternating current, pulsed direct current, or continuous direct current. Continuous direct current is preferred. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] The present invention will now be further described with reference to the following figures.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5a

Figure 5b

[0095] Description of the Drawings Figure 1 is a side cross-sectional view of the device according to the present invention. The device has a first punch 003 with a first punch surface 004 and a second punch 008 with a second punch surface 007. Punches 003 and 008 are made of solid graphite. Punch surfaces 004 and 007 are also made of graphite. The first punch 003 is located above the second punch 008. The first punch 003 is oriented such that the first punch surface 004 is horizontal and faces downward. The first punch 003 can be moved vertically by a first pressing means 001 connected via a first piston 002. The second punch 008 is oriented such that the second punch surface 007 is horizontal and faces upward. The second punch 008 can be moved vertically by a second pressing means 010 connected via a second piston 009. The first punch surface 004 and the second punch surface 007 can thus be moved towards each other along the direction of the compression axis 011. The device has a die 006 formed as a hollow graphite cylinder with an inner surface 005. The device has a power supply 012 adapted and configured to supply a DC current up to 20 kA, which is connected to the first punch 003 and the second punch 008. The sintering chamber of the present invention is formed as a cavity bounded by the first punch surface 004 from above, the second punch interior 007 from below, and the inner surface 005 on the side. In this case, both punch surfaces 004 and 007 are circular, the inner surface 005 is cylindrical, and thus the sintering chamber is cylindrical. The graphite layer of the inner surface 005 is not yet installed in Figure 1.

[0096] Figure 2 is a side cross-sectional view of the apparatus of FIG. 1 with the sintering chamber 013 loaded and ready for sintering. The sintering chamber 013 is defined by an inner surface 005 of a first punch surface 004 from above, a second punch surface 007 from below, and a die 006 to the side. The sintering chamber 013 thus has a cylindrical shape. The sintering chamber 013 is filled with a plurality of particles for sintering. The plurality of particles can be tamped and densified after being introduced into the sintering chamber. A layer of carbon material 014 is present on the inner surface 005 of the die 006. The layer 014 in this example thus constitutes a hollow cylindrical layer. In this case, additional layers 016 and 015 of carbon material are also present on the second punch surface 007 and the first punch surface 004, respectively. The additional layers 016 and 015 are optional. In practice, the lower layer 016 and the layer 014 inside the die 006 are introduced first, forming a recess in which the plurality of particles can be filled. The particles are then tamped, and an optional top layer 015 is placed thereon. The punch surfaces (004, 007) are then moved inward and abutted against the densified disk of particles coated with the graphite layer. For sintering, the punch surfaces (004, 007) are moved inward along the compression axis 011 as indicated by the arrows. The punch surfaces (004, 007) exert a force on the particles, resulting in the generation of pressure within the chamber. An electric current is passed from the power source 012 through the sintering chamber 013 (between the first punch surface 004 and the second punch surface 007).

[0097] Figure 3 shows the steps of the preparation process 200 of the ceramic body. In a first step a., 201, a plurality of particles are provided. The particle size d 50It may be, for example, 3 μm. An exemplary material of the particles is yttrium aluminum garnet (YAG). In a second step b., 202, the apparatus 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 graphite layer on the inner surface of the die is introduced prior to the particles. Optionally, the graphite layer on the second punch surface can also be introduced prior to the particles. The plurality of particles can be tamped down to compact the particles into a cylindrical shape. Optionally, the graphite layer for the first punch surface can be placed on top of the particles prior to below the first punch surface. In a fourth step d., 204, a pressure of, for example, 50 MPa is applied to the sintering chamber and a current of, for example, 80 kA is passed through the chamber to convert the particles into a formed ceramic body.

[0098] Figure 4 shows a cross-sectional view 300 of the sintering chamber 013. The cut is in a vertical direction along the diameter of the sintering chamber 013, passing through the compression axis 011, and the sintering chamber 013 is shown from the side. The die 006 is a hollow cylinder having a wall thickness 302. The graphite layer 014 is applied to the inner surface 005 of the die 006 to form a concentric hollow cylinder having a thickness 301 of, for example, 2 mm. 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.

[0099] Figures 5A and 5B show the core test 400 employed in this specification. Figure 5A shows a perspective view before the start of the test. The core drilling tool 401 is positioned above the first flat surface 402 of the flat ceramic sample 406. In this case, the flat ceramic sample 406 is in the form of a cylindrical disc. The tool 401 is oriented along an axis perpendicular to the first flat surface 402. The arrow 408 indicates the direction of movement of the tool 401 along the axis towards the flat ceramic sample 406. When contacting the flat ceramic sample 406, the core drilling tool 401 moves in a circular motion inside the core drilling region 407 having a diameter larger than the diameter of the tip 409 of the core drilling tool 401. The circular motion is parallel to the first flat surface 402 and will remove a cylindrical region from the flat ceramic sample 406. Further, the geometric center 405 of the first flat surface 402 is also the geometric center 405 of the core drilling region 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 flat ceramic sample 406 having a sample thickness 404. Figure 5B shows that the core drilling tool 401 has removed a cylindrical section 410 from the flat 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 cracks are first observed in the flat ceramic sample 406. The success level is determined as the ratio of the cored distance 403 at the end of the test to the total thickness of the flat ceramic sample 404, expressed as a percentage.

[0100] Test method C test The flat-shaped sample ceramic obtained in the example, having a first flat surface and a thickness perpendicular to the first flat surface, is cored to determine whether excessive internal stress exists. The coring tool 401 is, for example, a 10 mm diamond coring tool commercially available from Schott Diamantwerkzeuge GmbH (Stadtoldendorf, Germany). The tool is used in a commercially available CNC machine to cut a core into the part under test. The hole formed in the part by cutting the core is 56 mm to 60 mm and has a nominal diameter of 58 mm. The core is cut by passing the tool 401 over the surface of the part in a spiral pattern to drill a hole in the part. A suitable CNC machine that can be used for this test is available, for example, from DMG Mori Company Limited (Los Angeles, California, USA), such as its Ultrasonic 60 eVo linear model. Another supplier of suitable CNC machines is Fair Friend Ent. Co., Ltd. of Taiwan, which has models such as the Feeler HV-1650. The test ends as soon as either the core extends completely through the sample ceramic or cracks are observed in the sample ceramic. The success score is given as a percentage of the thickness of the core cut into the sample under test. A 100% success rating indicates that the internal stress, if present, is low, a success rating of over 75% and less than 100% indicates low internal stress, a success rating of 25% to 75% indicates a corresponding medium stress, and a success rating of less than 25% indicates high internal stress.

[0101] Particle size The particle size of the ceramic particles was determined using a Laser Scattering Particle Size Distribution Analyzer, Model LA-960, manufactured by Horiba Scientific (Piscataway, New Jersey, USA).

[0102] Layer thickness The thickness of the graphite layer can be measured with a physical measuring device such as a caliper.

[0103] Density and theoretical density The density of the ceramic body is measured in accordance with the standard ASTM B962-17. The theoretical density is calculated from X-ray diffraction (XRD) data. From the XRD data, the unit cell parameters a, b, and c are obtained. 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. Since the chemical structure of the ceramic body is known, its molecular weight is known. Using the aforementioned data, the theoretical density is calculated as follows. Theoretical density = (Molecular weight × Number of molecules per unit cell) / (Unit cell volume × Avogadro's number).

[0104] Average particle size The average particle size of the ceramic body is measured in accordance with the standard ASTM E112-13(2021).

Examples

[0105] Here, the mechanism of the present invention will be further described by citing specific examples. The present invention is not limited by the features of the examples, and those features are intended to provide specific embodiments of the present invention.

[0106] Example A An apparatus is provided according to the schematic diagram shown in FIG. 1. The die has a height of 1 m, and the punches each have a circular punch face with a diameter of 650 mm. The sintering chamber correspondingly had a cylindrical shape with a cross-sectional diameter of 650 mm. The graphite layer on the inner surface of the die was GRAFOIL® GTA flexible graphite with a total thickness of 1.9 mm, available from Neograf Solutions (Lakewood, Ohio). Neograf Solutions provides sheet-like flexible graphite in thicknesses of 0.13 mm, 0.25 mm, 0.38 mm, 0.51 mm, 0.64 mm, and 0.76 mm. In this example, two sheets of 0.76 mm and one sheet of 0.38 mm were used to make a total thickness of 1.9 mm.

[0107] Particle size d 50 Commercially available powders of yttrium oxide and aluminum oxide with a particle size d of 3 μm were mixed together, and 5 kg of the mixture was introduced into the sintering chamber, spread at a nearly horizontal height, and densified to a compression height of 20 mm with a force of about 40 tons. When sintered, this powder mixture forms yttrium aluminum garnet (YAG). Next, a mixture of commercially available powders in an amount of 27 kg was introduced into the sintering chamber where zirconia toughened alumina (ZTA) is produced during sintering and spread almost uniformly at a 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 a nearly uniform height of about 30 mm.

[0108] The punch was moved inward to reach the position shown in FIG. 2. The first and second punches were used to apply force to the powder in the sintering chamber to reach a sintering chamber pressure of about 15 MPa. A current of 40 kA to 70 kA supplied through the punch was passed through the sintering chamber for a total of 9 to 10 hours. The product was a flat cylindrical ceramic disk with a diameter of about 650 mm and a thickness of about 26 mm. This example was repeated for graphite layers on the inner surface of the die with the following thicknesses, namely 0.5 mm, 1 mm, 1.3 mm, 1.5 mm, 2.5 mm, 5 mm, 10 mm, and 20 mm.

[0109] The foregoing example was a three-layer cylindrical ceramic disk, but the method disclosed herein is also suitable for such disks in single-layer and two-layer forms.

[0110] Example B Example A was repeated, but the circular diameter of the punch surface was 100 mm.

[0111] Example C Example A was repeated, but the circular diameters of the punch surface were 200 mm, 350 mm, and 800 mm, respectively.

[0112] Results The results of Example A are shown in Table 1.

[0113] [Table 1]

[0114] The results of Example B are shown in Table 2.

[0115] [Table 2]

[0116] Considering the results in Table 2, the following can be understood. When considering the scale-up from the production of a 100-mm ceramic body to the production of a 650-mm ceramic body, the results in Table 2 do not suggest that the layer thickness should be changed to produce a 650-mm ceramic body with sufficient quality.

[0117] The example with a diameter of 200 mm was the same as the example with a diameter of 100 mm, that is, 100% success was uniformly achieved in the core test, and the energy consumption was uniform when the layer thickness was 2.5 mm or less. The results for a diameter of 350 mm were the same as the results for a diameter of 650 mm, except that the core test at 1.5 mm was 100% successful. The results for a diameter of 800 mm were the same as the results for a diameter of 650 mm, except that crushing was observed in the core test at a thickness of 1 mm and the power supply was insufficient to sinter the product in the tests at thicknesses of 5 mm and 10 mm.

Explanation of Signs

[0118] 001 First pressing means 002 First piston 003 First punch 004 First punch surface [[ID=1,5]]005 Inner surface 006 Die 007 Second punch surface 008 Second punch 009 Second piston 010 Second pressing means 011 Compression axis 012 Power supply 013 Sintering chamber 014 Layer 015, 016 Further layer 200 Preparation process of ceramic body 201 Step a. 202 Step b. 203 Step c. 204 Step d. 300 Cross-section of sintering chamber 301 Layer thickness 302 Die thickness 303 Sintering chamber diameter 400 Core test configuration 401 Core ring tool 402 First flat surface 403 Drill depth 404 Sample thickness 405 Geometric center 406 Flat ceramic sample 407 Coring area 408 Movement direction perpendicular to the flat ceramic sample 409 Tip of the coring tool 410 Cylindrical section removed from the flat ceramic sample

Claims

1. An apparatus having a sintering chamber (013), wherein the sintering chamber (013) comprises the following apparatus parts, namely, i. The first punch surface (004) of the first punch (003), ii. The second punch surface (007) of the second punch (008), iii. The inner surface (005) of the die (006) is bounded by, The punches (003, 008) are configured to apply a pressure of at least 1 MPa along the compression axis (011) to a target in the sintering chamber (013), The first punch (003) and the second punch (008) are connected to a power supply (012) which is adapted and configured to supply a current of at least 5 kA. The first punch (003) and the second punch (008) each contain 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 300 mm to 2000 mm perpendicular to the compression shaft (011), At least a portion of the inner surface (005) of the die (006) contains carbon material C δ A layer δ exists, and the average thickness D of the layer δ is determined over the inner surface (005) of the die (006). δ It has, D δ The device is in the range of 1.1 mm or more and less than 5 mm.

2. The apparatus according to claim 1, wherein the layer δ is composed of two or more stacked sublayers.

3. The apparatus according to claim 1, wherein both the punch (003, 008) and the die (006) are at least partially present in a vacuum chamber, in a non-oxidizing atmosphere, or both.

4. The sintering chamber (013) has a diameter D Ｃ It has the diameter D Ｃ and the average thickness D of the layer δ Ratio D Ｃ : D δ The apparatus according to claim 1, wherein the ratio is in the range of 100:1 to 350:

1.

5. The following is a summary, that is, a. A layer ε made of carbon material C exists on at least a part of the first punch surface (004). ε ​ b. A carbon material C is placed on at least a portion of the second punch surface (007). θ The apparatus according to claim 1, wherein one or both of the following conditions are met: a layer θ made of materials exists.

6. The following is a summary, that is, a. The first punch (003) is at least 99% by weight of carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the first punch (003). b. The second punch (008) is at least 99% by weight of carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the second punch (008). c. The die (006) is at least 99% by weight of carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the die (006). The apparatus according to claim 1, wherein one or more of the following are satisfied: d. The layer δ is at least 99% by weight carbon, based on the total weight of carbon atoms in any chemical form and the total weight of the layer δ.

7. The die is made of carbon material C γ It is made of, and as follows, a. C δ and C γ The anisotropy values ​​are different. b. C δ and C γ The specific conductivity determined in the direction parallel to the compression axis (011) is different. c. C δ and C γ The relative conductivity determined in the direction perpendicular to the inner surface (005) is different. d. C δ and C γ The specific thermal expansion coefficients determined in the direction parallel to the compression axis (011) are different. e. C δ and C γ The specific thermal expansion coefficients determined in the direction perpendicular to the inner surface (005) are different. The apparatus according to claim 1, wherein one or more of the following conditions are met: f. The carbon material C δ and the carbon material C γ have different ash content as determined by ASTM C-561.

8. A process for preparing a ceramic body, a. A step of providing multiple particles, b. The step of providing the apparatus described in claim 1, c. The step of introducing the particles into the sintering chamber (013) of the apparatus, d. A process comprising the step of applying a pressure P in the range of 1 MPa to 80 MPa and a current I in the range of 1 kA to 100 kA in order to obtain the ceramic body.

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

10. The following, in other words a. The density value obtained by dividing by the theoretical density which is less than 1.

0. b. Average particle size less than 5 μm, c. A ceramic body that satisfies at least one or all of the following conditions regarding the standard deviation of the average particle size distribution in the range of 1.8 ± 2 μm to 2.2 ± 2 μm.

11. An assembly comprising the ceramic body described in claim 10.

12. The aforementioned assembly is a. Plasma etcher, b. Plasma processing chamber (etching or deposition process), c. Wear plates for bearings, d. The assembly according to claim 11, selected from the group consisting of a mill liner for a grinding mill.

13. Use of a graphite layer with a thickness in the range of 1.1 mm to less than 5 mm for preparing a ceramic body having an extent of 300 mm to 2000 mm by spark plasma sintering.

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