Sintering apparatus having a low surface roughness

Abstract

An apparatus having a sintering chamber (013), wherein the sintering chamber (013) is bounded by the following apparatus parts, namely: i. the first punch surface (004) of the first punch (003), and ii. the second punch surface (007) of the second punch (008), and iii. the inner surface (005) of the die (006), and is bounded thereby, The punches (003, 008) are adapted and configured to apply a pressure of at least 1 MPa along the compression axis (011) to a target within the sintering chamber (013), The first punch (003) and the second punch (008) are connected to a power supply (012) adapted and configured to provide a current of at least 10 kA, The first punch (003) and the second punch (008) 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 at least 300 mm perpendicular to the compression axis (011), The die has a surface portion χ having an area of at least 5 cm 2 and located on the inner surface of the die, and the surface portion χ has an average surface roughness (Sa) in the range of 1 μm to 8 μm.

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 a sintering apparatus, a sintering process, a ceramic body product, an assembly including a ceramic body, and using a die of the apparatus with a low surface roughness in the sintering process.

Background Art

[0002] The sintering method provides a path for forming a solid body from particles by applying heat and pressure. In one method, often called spark plasma sintering (SPS), the 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] It is an object of the present invention to provide an improved process for preparing a ceramic body. In particular, it is an object of the present invention 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 a reduced waste rate.

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

[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 face of the first punch, and ii. the second punch face of the second punch, and iii. the inner surface of the die, and is bounded by, the punch is 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 in the sintering chamber. The punch may be adapted and configured to apply up to 50 MPa, or even more, the first punch and the second punch are connected to a power supply adapted and configured to supply a current of at least 10 kA, more preferably at least 50 kA, and most preferably at least 60 kA. The power supply may be adapted and configured to provide 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 punch, the sintering chamber has a cross-sectional width W of at least 300 mm, preferably at least 500 mm, more preferably at least 700 mm, perpendicular to the compression axis. W can reach a size of 2000 mm or more. Preferably this is 1500 mm or less, more preferably 900 mm or less, the die 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, and the surface portion χ 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, preferably in the range of 3 μm to 6 μm, and more preferably in the range of 3 μm to 5 μm.

[0016] In an aspect of the first embodiment, the surface portion χ has an area of at least 10 cm 2 , more preferably an area of at least 50 cm2 and more preferably has an area of at least 100 cm 2 is preferred.

[0017] 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, 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 second embodiment of the present invention, which preferably depends on the first embodiment of the present invention.

[0018] In an aspect of the second embodiment, the surface portion α has an area of at least 10 cm 2 and more preferably has an area of at least 50 cm 2 and more preferably has an area of at least 100 cm 2 is preferred. In an aspect of the second embodiment, it is preferred that the surface portion α at least partially overlaps the die contact surface of the first punch.

[0019] In a preferred embodiment of the device, the surface portion α at least partially overlaps the first punch surface. This preferred embodiment is the third embodiment of the present invention, which preferably depends on the second embodiment of the present invention.

[0020] 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, which preferably depends on the third embodiment of the present invention.

[0021] In a preferred embodiment of the device, the second punch has an area of at least 5 cm 2has a surface portion β, 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, 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, which preferably depends on any one of the first to fourth embodiments of the present invention. In the aspect of the fifth embodiment, the surface portion β preferably has an area of at least 10 cm 2 and more preferably has an area of at least 50 cm 2 and even more preferably has an area of at least 100 cm 2 . In the aspect of the fifth embodiment, it is preferable that the surface portion β at least partially overlaps with the die contact surface of the second punch. In the aspect of the fifth embodiment, it is preferable that the surface portion β at least partially contacts the surface portion χ.

[0022] 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, which preferably depends on the fifth embodiment of the present invention.

[0023] In a preferred embodiment of the device, the surface portion χ has at least one or all of the following characteristics. 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. b. A shape 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. c. An arithmetic mean peak curvature (Spc) of at least 4000 mm -1 preferably at least 7000 mm -1 and even more preferably at least 8000 mm -1 . d. A developed interface area ratio (Sdr) of at least 4, more preferably at least 12, and even more preferably at least 14.

[0024] This preferred embodiment is the seventh embodiment of the present invention, which preferably depends on any one of the first to sixth embodiments of the present invention. In the 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.

[0025] In a preferred embodiment of the device, the surface portion α and / or the surface portion β has at least one or all of the following characteristics. a. A maximum height (Sz) in the range of 20 μm to 100 μm, preferably in the range of 35 μm to 87 μm, more preferably in the range of 44 μm to 62 μm. b. A shape aspect ratio (Str) in the range of 0.01 to 0.75, preferably in the range of 0.1 to 0.65, more preferably in the range of 0.41 to 0.5. c. An arithmetic mean peak curvature (Spc) of at least 4000 mm -1 preferably at least 7000 mm -1 more preferably at least 8000 mm -1 d. A developed interface area ratio (Sdr) of at least 4, more preferably at least 12, still more preferably at least 14.

[0026] This preferred embodiment is the eighth embodiment of the present invention, which preferably depends on any one of the second to seventh embodiments of the present invention. In the 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.

[0027] ​In a preferred embodiment of the device, both the punch 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 ninth embodiment of the present invention, which preferably depends on any one of the first to eighth embodiments of the present invention.

[0028] In a preferred embodiment of the device, the power supply is adapted and configured to supply a DC voltage. 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.

[0029] 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 contains at least 50% by weight, more preferably at least 90% by weight, and even more preferably 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.

[0030] 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 aspects 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.

[0031] In a preferred embodiment of the device, the device includes one or more additional device parts selected from the following list: a. A housing b. Vacuum equipment c. A hydraulic piston.

[0032] This preferred embodiment is the twelfth embodiment of the present invention, which preferably depends on any one of the first to eleventh embodiments of the present invention. In the 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.

[0033] The thirteenth embodiment of the present invention is a process for the preparation of a ceramic body, a. providing a plurality of particles; b. providing an apparatus according to the present invention, preferably an apparatus according to any one of the first to twelfth embodiments of the present invention; c. introducing the particles into a sintering chamber; 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, more preferably in the range of 25 kA to 100 kA, even more preferably in the range of 50 kA to 100 kA, to the plurality of particles in the sintering chamber to obtain a ceramic body.

[0034] 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 fourteenth embodiment of the present invention, which preferably depends on the thirteenth embodiment of the present invention.

[0035] The fifteenth embodiment of the present invention is a ceramic body obtainable by a process according to the present invention, preferably a process according to the thirteenth or fourteenth embodiment of the present invention.

[0036] In a preferred embodiment of the ceramic body, at least one or all of the following are satisfied for the ceramic body: a. the value of the density divided by the theoretical density, which 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, and still more preferably 1 μm to 3 μm, c. A standard deviation of the average particle 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.

[0037] This preferred embodiment is the 16th embodiment of the present invention, which preferably depends on the 15th embodiment of the present invention. In the aspect 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 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.

[0038] The 17th embodiment of the present invention is an assembly including a ceramic body according to the present invention, preferably a ceramic body according to the 15th or 16th embodiment of the present invention.

[0039] 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, and d. A mill liner of a grinding mill.

[0040] This preferred embodiment is the 18th embodiment of the present invention, which preferably depends on the 17th embodiment of the present invention. In the aspect of the 18th 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.

[0041] The 19th embodiment of the present invention is the use of a die for preparing a ceramic body having a spread of at least 300 mm by spark plasma sintering, the die having a surface portion with an area of at least 5 cm 2 and having an average surface roughness (Sa) in the range of 1 μm to 8 μm, preferably in the range of 2 μm to 7 μm, preferably in the range of 3 μm to 6 μm, and more preferably in the range of 3 μm to 5 μm. In an aspect of the 19th embodiment, the surface area is at least 10 cm 2 , more preferably at least 50 cm 2 , still more preferably at least 100 cm 2 in area.

Mode for Carrying Out the Invention

[0042] The following abbreviations are used in the description. AC (alternating current), DC (direct current).

[0043] 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 the application of an electric current.

[0044] 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. 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.

[0045] Apparatus The apparatus of the present invention is adapted and configured to sinter particles to produce a solid body. The apparatus comprises at least a first punch, a second punch, and a die. The apparatus has a sintering chamber.

[0046] 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 a first punch, a second punch face of a second punch, and an inner face of the die. The sintering chamber may be bounded by only the first punch face, the second punch face, and the inner face, or may be additionally bounded by one or more further surfaces. The sintering chamber is preferably bounded by only the first punch face, the second punch face, and the inner face.

[0047] 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.

[0048] 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.

[0049] The punch is preferably adapted and configured to apply a 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 provide 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 50 MPa or even more.

[0050] 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.

[0051] The punch preferably has conductivity. The punch is preferably adapted and configured to supply a current of at least 10 kA, more preferably at least 50 kA, and most preferably at least 60 kA. The power supply may be adapted and configured to provide a current up to 100 kA or even more.

[0052] The punch is preferably made of a carbon material and most preferably made of 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 contain one or more selected from layers and regions of materials other than carbon.

[0053] Die The device of the present invention has a die. The die has an inner surface that bounds the sintering chamber.

[0054] In one embodiment, the die has conductivity. The die preferably has anisotropic conductivity and preferably has a material arrangement direction axis that is substantially aligned with the compression axis.

[0055] 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.

[0056] 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 preferably contains one or more additional Group 14 elements 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 additional Group 14 element(s) preferably are present in 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 are present in a total content of 1 wt% or less, more preferably 0.5 wt% or less, and most preferably 0.1 wt% or less.

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

[0058] The die may be a single piece or multiple pieces, but is preferably a single piece. The die preferably is a single continuum and more preferably a single cylindrical body. The die preferably has 2 to 10 pieces, more preferably 2 to 5 pieces, even more preferably 2 to 3 pieces, and most preferably 2 pieces.

[0059] 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.

[0060] Arrangement direction The apparatus of the present invention has a compression axis. The apparatus is preferably adapted and configured to apply a force to the sintering chamber along the direction of the compression axis.

[0061] 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.

[0062] In one embodiment, the compression axes are substantially perpendicular, preferably with the first punch positioned above the second punch. In aspects of this embodiment, the first punch face is preferably the lower face of the first punch. In another aspect of this embodiment, the first punch face is substantially horizontal. In another aspect of this embodiment, the second punch face is preferably the upper face of the second punch. In another aspect of this embodiment, the second punch face is substantially horizontal.

[0063] Die contact surface The die contact surface of the punch is defined as the surface of the punch that is adapted and configured to physically contact the inner surface of the die during the sintering process. A preferred die contact surface is parallel to the compression axis.

[0064] 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 cracks. 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.

[0065] 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.

[0066] Preferred oxide ceramics can be single-element oxides or mixed oxides of two or more elements. The oxide ceramics may contain a certain amount of nitride content or carbide content, or both. The oxide ceramics may not contain nitrides, may not contain carbides, or may not contain both. 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 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.

[0067] Preferred nitride ceramics can be single-element nitrides or mixed nitrides of two or more elements. The nitride ceramics may contain a certain amount of oxide content or carbide content, or both. The nitride ceramics may not contain oxides, may not contain carbides, or may not contain both. 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 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.

[0068] 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.

[0069] 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 yttrium content may be up to 50 wt% or even more. 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 relative 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 yttrium oxide content may be up to 50 wt% or even more.

[0070] 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.

[0071] 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.

[0072] Some preferred mixed oxides are one or more selected from the group consisting of zirconium silicate oxide, hafnium aluminate oxide, hafnium silicate oxide, titanium silicate oxide, lanthanum silicate oxide, lanthanum aluminate oxide (LAO), yttrium silicate oxide, titanium silicate oxide, tantalum silicate oxide, oxynitride, barium titanate, lead titanate, and lead zirconate titanate.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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 one or more selected from the group consisting of forsterite.

[0077] 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. 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.

[0078] The preferred size of the particles ranges from 0.1 μm to 20 μm. The preferred average size of the particles ranges from 0.3 μm to 7 μm, more preferably from 0.5 μm to 5 μm.

[0079] 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 can range from 15 MPa to 30 MPa. Pressures up to approximately 80 MPa or even higher can be applied.

[0080] 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, even more preferably at least 50 kA is applied to pass through the sintering chamber. Currents up to 100 kA or even higher can be applied.

[0081] 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.

[0082] In an aspect of the present invention, during the process for preparing the ceramic body according to the present invention, it is preferable that a potential difference is applied between the first punch surface and the second punch surface of the apparatus according to the present invention, and the potential difference ranges from 5 V to 10 V, more preferably from 5 V to 7 V, even more preferably from 6 V to 6.5 V.

[0083] 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.

[0084] 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.

[0085] In one aspect of the invention, it is preferred that the power supply is a rectified DC power supply. A rectified DC power supply is preferably understood to mean a power supply adapted and configured to convert alternating current to direct current. Examples of rectified DC power supplies are power supplies adapted and configured to perform half-wave rectification, full-wave rectification (e.g., bridge rectifiers), or both. Preferred rectified DC power supplies include thyristors, silicon controlled rectifiers, or both.

[0086] The power supply is preferably adapted and configured to provide a current of at least 5 kA, more preferably at least 10 kA, even more preferably at least 50 kA, still more preferably at least 60 kA, and yet even more preferably at least 100 kA.

Brief Description of the Drawings

[0087] The present invention will now be further described with reference to the following drawings. The drawings are not drawn to scale.

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

[0088] Figure Description of the surface Figure 1A is a side cross-sectional view of an apparatus 100 according to the present invention. The apparatus has a first punch 003 having a first punch surface 004 and a second punch 008 having a second punch surface 007. Punches 003 and 008 are fabricated from solid graphite. 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 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 are thus movable towards each other along the direction of the compression axis 011.

[0089] The apparatus has a die 006 formed as a hollow graphite cylinder having an inner surface 005. The apparatus has a power supply 012 adapted and configured to supply a DC current and 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 inner 007 from below, and the inner surface 005 laterally. In this case, both punch surfaces 004 and 007 are circular and the inner surface 005 is cylindrical, and thus the sintering chamber is cylindrical.

[0090] Figure 1B is an enlarged view of the first punch (003) and the second punch (008) of Figure 1A 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 first punch 008 is also circular).

[0091] Figure 2 shows, which shows a side cross-sectional view of the apparatus 100 of FIG. 1A with the sintering chamber 013 loaded and ready for sintering. The sintering chamber 013 is defined by a first punch surface 004 from above, a second punch surface 007 from below, and the inner surface 005 of the die 006 on 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. The punch surfaces (004, 007) are then moved inward and abutted against the disk of the densified particles. For sintering, the punch surfaces (004, 007) are moved inward along the compression axis 011 as shown by the arrows. The punch surfaces (004, 007) apply a force to the particles, resulting in the generation of pressure inside the chamber. A current is applied from the power source 012 to pass through the sintering chamber 013 (between the first punch surface 004 and the second punch surface 007).

[0092] dam The inner surface 005 of the die 006 is in contact with the die contact surfaces (014, 015) of the first punch 003 and the second punch 008 before and during the sintering process.

[0093] FIG. 3 shows the steps of the preparation process 200 of the ceramic body. In the first step a., 201, a plurality of particles are provided. The particle size d 50 can be, for example, 3 μm. An exemplary material of the particles is yttrium aluminum garnet (YAG). In the second step b., 202, the apparatus described in the present disclosure is provided. The sintering chamber of the apparatus can have a diameter of, for example, 500 mm. In the third step c., 203, a plurality of particles are introduced into the sintering chamber of the apparatus. The plurality of particles can be tamped to densify the particles into a cylindrical shape. In the 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.

[0094] 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 301. The die thickness 301 and the diameter 302 of the sintering chamber 013 are each measured in a radial direction perpendicular to the compression axis 011.

[0095] Figures 5A and 5B show a core test 400 employed in this specification. Figure 5A shows a perspective view before the start of the test. The core ring 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 disk. 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 ring tool 401 moves in a circular motion inside a core ring region 407 having a diameter larger than the diameter of the tip 409 of the core ring 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 ring region 407. Figure 5B shows a side cross-sectional view 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 ring 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 a crack is 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.

[0096] good Preferred positional relationship in, in this case, the first punch (003) and the second punch (008) are arranged with respect to the die 006 such that the difference in distances 016 and 017 is less than 3% of each other (as indicated by the arrows). This positional relationship can be achieved by selecting a die 006 with an inner surface 006 having a sufficiently large average surface roughness (Sa). In addition to selecting a sufficiently large average surface roughness for the inner surface 005, further improvement of the positional relationship can also 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.

[0097] dam If the inner surface 005 of the die 006 is overly smooth when , that is, when the value of the average surface roughness (Sa) is too small, in the positional relationship when there is, Distance 016 is significantly larger than distance 017.

[0098] Test method Core 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, with models such as Feeler HV-1650. The test ends as soon as the core extends completely through the sample ceramic or when cracks are observed in the sample ceramic, whichever is earlier. The success score is given as a percentage of the thickness of the core cut into the sample under test. A success rating of 100% indicates that the internal stress, if any, was 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.

[0099] Surface roughness The average surface roughness Sa (also known as the arithmetic mean height) is measured using the standard ISO 25178:2019. The maximum height (Sz), shape aspect ratio (Str), arithmetic mean peak curvature (Spc), and developed interface area ratio (Sdr) are also measured using the standard ISO 25178:2019. For the measurement of surface roughness, a VK-X200 3D laser scanning microscope commercially available from KEYENCE CORPORATION (Japan) is used.

[0100] Particle size and average particle size The particle size and average particle size of the ceramic particles were determined using a Laser Scattering Particle Size Distribution Analyzer, Model LA-960, manufactured by Horiba Scientific (Piscataway, New Jersey, USA).

[0101] Current intensity, potential difference, and resistance The current intensity is measured using a MicroFUSION 400A silicon-controlled rectifier (SCR) commercially available from Control Concepts Inc. (USA). The potential difference is measured using a DSCA31 analog voltage input signal conditioner commercially available from Dataforth Corporation (USA). The resistance is obtained by dividing the potential difference by the current intensity.

[0102] Density and theoretical density The density of the ceramic body is measured according to 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. The molecular weight of the ceramic body is known since its chemical structure is known. Using the above data, the theoretical density is calculated as follows.

[0103] 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 according to the standard ASTM E112-13 (2021).

Example

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

[0106] Example A An apparatus according to the schematic diagram shown in FIG. 1 is provided. The die has a height of 1 m, and the punches each have a circular punch surface with a diameter of 650 mm. Correspondingly, the sintering chamber had a cylindrical shape with a cross-sectional diameter of 650 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 substantially 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 commercially available powder mixture was introduced into the sintering chamber in an amount of 27 kg, where zirconia toughened alumina (ZTA) is generated during sintering, and spread substantially uniformly at a height of about 100 mm. Finally, a powder mixture for forming YAG and ZTA was introduced into the sintering chamber in an amount of 7 kg and spread at a substantially uniform height of about 30 mm.

[0108] The punch was moved inward to reach the position shown in FIG. 2. The powder in the sintering chamber was pressured by the first and second punches to reach a sintering chamber pressure of about 15 MPa. A current of 40 kA - 70 kA supplied through the punch was passed through the sintering chamber for a total of 9 hours - 10 hours. The product was a flat-shaped cylindrical ceramic disk with a diameter of about 650 mm and a thickness of about 26 mm.

[0109] As shown in Table 1, this example was repeated using various values for the average surface roughness (Sa) of the inner surface of the die and the die contact surfaces of the first and second punches. 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 particle size refers to the size of the microcrystals or crystals of the ceramic body.

[0110] 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.

[0111] Example B Example B is carried out in the same manner as Example A, but the circular diameter of the punch surface is 100 mm. The results are also shown in Table 1 below. The resistance in Table 1 is the resistance measured for the die.

[0112]

Table 1

[0113] If the surface roughness value is too small, this will result in very limited friction between the die and the punch. As a result, the die and the punch will be misaligned with each other, causing serious problems in the production of the ceramic body. If the surface roughness value is too large, this will lead to an increase in the electrical contact between the die and the punch, which in turn will result in the generation of additional heat in the sintering chamber during the production of the ceramic body. The resulting ceramic body will be of very poor quality.

[0114] Considering the results in Table 1 for a punch surface having a circular diameter of 100 mm, it is not suggested that the surface roughness should be limited within a specific range to produce a sufficiently high-quality ceramic body having a diameter of 650 mm.

[0115] Further Examples The above Examples A and B were repeated, but the circular diameters of the punch surfaces were 300 mm and 500 mm respectively. In the case of 300 mm, it was found that the results were very similar to those in the case of a diameter of 100 mm (Example B). The results for a diameter of 500 mm were very similar to the results of Example A.

Description of Symbols

[0116] 100 Device according to the present invention 001 First pressing means 002 First piston 003 First punch 004 First punch surface 005 Inner surface of die 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 Die contact surface of the first punch 015 Die contact surface of the second punch 016 Distance 017 Distance 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 Wall thickness of die 302 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 Core ring area The direction of movement perpendicular to the flat ceramic sample 409 The tip of the coring tool 410 The cylindrical section removed from the flat ceramic sample

Claims

1. An apparatus having a sintering chamber (013), wherein the sintering chamber (013) is bounded by the following apparatus parts, namely: i. a first punch surface (004) of a first punch (003), ii. a second punch surface (007) of a second punch (008), iii. an inner surface (005) of a die (006), and is bounded by, 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 (013), the first punch (003) and the second punch (008) are connected to a power supply (012) adapted and configured to supply a current of at least 10 kA, the first punch (003) and the second punch (008) 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 at least 300 mm perpendicular to the compression axis (011), The die has a surface portion χ with an area of at least 5 cm ２ The surface portion χ is located on the inner surface of the die, and the surface portion χ has an average surface roughness (Sa) in the range of 1 μm to 8 μm. Device.

2. 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. The apparatus according to claim 1.

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

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

5. 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. The apparatus according to any one of claims 1 to 4.

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

7. The apparatus, a. housing, b. vacuum equipment, c. hydraulic piston, and includes one or more additional apparatus parts selected from the list consisting of, the apparatus according to any one of claims 1 to 6.

8. A process for the preparation of a ceramic body, comprising: a. providing a plurality of particles; b. providing an 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 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. A ceramic body obtainable by the process according to claim 8 or 9.

11. 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, c. The standard deviation of the average particle size distribution in the range of 1.8 ± 2 μm to 2.2 ± 2 μm, wherein at least one or all of the above are satisfied, the ceramic body according to claim 10.

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

13. The assembly is a. A plasma etcher, b. A plasma processing chamber (etching or deposition process), c. A wear plate for a shaft, and d. A mill liner of a grinding mill, and is selected from the group consisting of, the assembly according to claim 12.

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

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