Ultrafast high-temperature sintering equipment

Abstract

The invention relates to an ultra-fast high-temperature sintering apparatus comprising: first and second carbon-containing thermally conductive substrates arranged at a distance from each other so as to provide a space for receiving a substrate to be sintered, and arranged between a third thermally conductive substrate and a fourth thermally conductive substrate; the heating device is used for heating the third heat conduction substrate and / or the fourth heat conduction substrate so as to respectively heat the first heat conduction substrate and / or the second heat conduction substrate, and the third heat conduction substrate and the fourth heat conduction substrate independently comprise one or more metal nitrides and / or metal oxides.

Description

Technical Field

[0001] The invention relates to a sintering device, in particular to an ultra-fast high-temperature sintering device. Background Art

[0002] Conventional sintering methods are usually carried out in so-called batch production furnaces, where they are heated to the required sintering temperature, which depends on the composition of the material to be sintered. The disadvantages of such batch production furnaces include long heating and cooling times (i.e., low heating rates and low cooling rates), difficult temperature and heat distribution (i.e., uniformity of temperature) control, high energy consumption (due to long heating times) and increased total processing time. This results in uneven sintering and therefore limited sintering quality. This also results in lower throughput (less number of sintered objects produced within a certain time period), making these sintering techniques less suitable for industrial-scale applications.

[0003] Recently, new sintering methods and improved sintering equipment have been developed, including microwave assisted sintering, spark plasma sintering and flash sintering. However, microwave assisted sintering depends largely on the microwave absorption properties of the material to be sintered, which limits its applicability. Spark plasma sintering equipment requires a mold to compress the material during sintering, which limits the geometry of the parts to be sintered and the scalability. In addition, due to the applied pressure, it is not suitable for sintering complex three-dimensional structures. Flash sintering equipment is capable of heating at a heating rate of up to 10,000°C / min, but requires expensive platinum electrodes. Flash sintering equipment is also less suitable for sintering parts with complex geometries, such as three-dimensional structures.

[0004] CN208567515 discloses a sintering device, which includes a furnace body from the inside to the outside, the furnace body including a graphite heating body, an electrical insulation layer (which is a heat-insulating high-temperature rock wool) and a heat insulation layer (which first includes hard graphite felt and then includes an aluminosilicate fiber layer).

[0005] US2007 / 0202455 discloses a firing apparatus comprising a muffle furnace having a heater or heat generator at two parallel sides. The muffle furnace and the heater or heat generator are surrounded by a plurality of insulating layers made of carbon. The heater may be made of graphite, or may be a carbon member. Another embodiment discloses a carbon member that acts as both a muffle furnace and a heater.

[0006] Another recently developed sintering equipment is the ultrafast high temperature sintering equipment.

[0007] WO2020 / 236767 discloses a rapid high temperature sintering system and method. The substrate to be sintered is placed between two heat-conducting carbon elements, and the distance between each heat-conducting carbon element and the substrate is 0 to 10 mm. The heat-conducting carbon elements are heated to a temperature between 500°C and 3000°C by electric current, and the sintering is performed within 1 second to 1 hour by heating the substrate with the heated heat-conducting carbon elements.

[0008] A disadvantage of the aforementioned ultrafast high temperature sintering apparatus is that self-supporting substrates (i.e. in the absence of a support or carrier) are difficult to sinter. In particular, in the case of flat self-supporting substrates, it is difficult to maintain the flatness of the substrate during sintering with the aforementioned apparatus. In other words, when sintering in the absence of a carrier or support, the sintered substrates obtained with the aforementioned apparatus tend to bend, curve, and may even crack, or may begin to break when trying to flatten the sintered substrate after sintering. Summary of the invention

[0009] The present invention aims to overcome one or more of the above disadvantages. An object of the present invention is to provide a sintering device that allows a reduced sintering time and / or an improved control of the sintering conditions, in particular the sintering temperature. A further object is to provide a sintering device that allows a more uniform sintering. A further object is to provide a sintering device that is capable of sintering thin (i.e., with a thickness of less than 100 μm) and / or flat substrates without causing damage or deformation to the sintered substrate, i.e., thereby maintaining flatness. A further object is to provide a sintering device with reduced energy consumption.

[0010] The term "substrate" as a part of a sintering device is used in the present disclosure for a component or a layer of the sintering device, in particular a layer having a sheet-like shape.

[0011] Advantageously, the sintering device is an ultrafast high temperature sintering device. The term "ultrafast sintering" is used in the present disclosure for a sintering device that can be heated at a heating rate of at least 50°C / s, and optionally cooled at a cooling rate of at least 50°C / s. The term "high temperature sintering device" is used in the present disclosure for a sintering device that can be heated to a temperature of at least 750°C, preferably at least 900°C, such as between 750°C and 1400°C, more preferably between 900°C and 1250°C.

[0012] According to an aspect of the present invention, a sintering apparatus according to the accompanying claims is disclosed.

[0013] The sintering apparatus according to the present disclosure includes a first heat conductive substrate and a second heat conductive substrate, which are arranged at a distance from each other so as to provide a space for receiving a substrate (ie, an article or object) to be sintered.

[0014] The first heat-conducting substrate and the second heat-conducting substrate are arranged between the third heat-conducting substrate and the fourth heat-conducting substrate. In other words, the third heat-conducting substrate and the fourth heat-conducting substrate are arranged at the outer surfaces of the first heat-conducting substrate and the second heat-conducting substrate, respectively.

[0015] The first thermally conductive substrate and the second thermally conductive substrate include carbon.

[0016] The third thermally conductive substrate and the fourth thermally conductive substrate independently comprise one or more metal nitrides and / or metal oxides. Advantageously, the third thermally conductive substrate and the fourth thermally conductive substrate independently comprise one or more single-crystalline metal nitrides and / or single-crystalline metal oxides.

[0017] Advantageously, the (single-crystalline) metal nitride comprises (single-crystalline) boron nitride and / or (single-crystalline) aluminum nitride. Advantageously, the (single-crystalline) metal oxide comprises (single-crystalline) aluminum oxide and / or (single-crystalline) sapphire, such as single-crystalline sapphire.

[0018] Advantageously, the first heat-conducting substrate at least partially contacts the third heat-conducting substrate. Alternatively or additionally, and advantageously, the second heat-conducting substrate at least partially contacts the fourth heat-conducting substrate. In the present invention, "at least partially contacting" means that the two substrates are in contact on at least a portion of the respective surfaces of the substrates facing each other, i.e., in contact with each other.

[0019] The sintering device also includes a heating device. In the use of the device, the heating device is arranged or provided for heating the third heat-conducting substrate and / or the fourth heat-conducting substrate. The heating device is arranged so that, in use, it can heat the third heat-conducting substrate and / or the fourth heat-conducting substrate at a heating rate of at least 50°C / s. The heating device is arranged so that, in use, it can heat the third heat-conducting substrate and / or the fourth heat-conducting substrate to a temperature between 750°C and 1400°C, preferably between 900°C and 1250°C. The heating device is arranged so that, in use, when heating the third heat-conducting substrate and / or the fourth heat-conducting substrate, the first heat-conducting substrate and / or the second heat-conducting substrate are heated respectively.

[0020] Advantageously, the sintering apparatus further comprises a first conductor at an outer surface of the third heat conducting substrate. Alternatively or additionally, and advantageously, the sintering apparatus further comprises a second conductor at an outer surface of the fourth heat conducting substrate.

[0021] Advantageously, when the first and second conductors are provided, they together at least partially, and preferably completely, surround the first, second, third and fourth heat conducting substrates and the space (ie, the space between the first and second heat conducting substrates).

[0022] Advantageously, the first conductor and the second conductor comprise carbon. Examples of carbon-containing conductors include, but are not limited to, graphite, carbon fibers, carbon nanotubes, or a combination of two or more thereof. The first conductor and the second conductor may have the same or different compositions.

[0023] Advantageously, the sintering device further comprises a first support device arranged at the outer surface of the first conductor. Alternatively or additionally, and advantageously, the sintering device further comprises a second support device arranged at the outer surface of the second conductor. Advantageously, when arranged, each of the first support device and the second support device independently comprises a thermally insulating and electrically insulating ceramic substrate and at least one metal support component. Advantageously, the support device is arranged so that the metal support component contacts the thermally insulating and electrically insulating ceramic substrate and the conductor. In other words, when the first support device and the second support device are arranged respectively, they are arranged so that their metal support components contact their thermally insulating and electrically insulating ceramic substrates and the surfaces of the first and second conductors facing the support device (i.e., the outer surfaces of the respective conductors). Advantageously, the support device is arranged so that the metal support component and the thermally insulating and electrically insulating ceramic substrate mechanically support the conductor.

[0024] Advantageously, the thermally and electrically insulating ceramic substrate comprises alumina (ie, aluminum oxide).

[0025] Advantageously, the metal support member comprises tungsten or an alloy thereof. Non-limiting examples of tungsten-containing alloys are tungsten-nickel-iron alloys, tungsten-nickel-copper alloys and tungsten carbide alloys.

[0026] Advantageously, when the sintering apparatus comprises a first conductor and / or a second conductor, the heating means comprises means for inducing a current to the first conductor and / or the second conductor. Advantageously, in use, when a current is induced to the first conductor and / or the second conductor, the third thermally conductive substrate and / or the fourth thermally conductive substrate is heated advantageously by means of Joule heating. Joule heating is also known as resistive heating or ohmic heating. Advantageously, when a current is induced (in use of the apparatus) to the first conductor and / or the second conductor, any ohmic or resistive losses in the first conductor and / or the second conductor are dissipated in the form of heat, which heats the third thermally conductive substrate and / or the fourth thermally conductive substrate.

[0027] Advantageously, in addition to the first conductor and / or the second conductor, the sintering device further comprises a third conductor and a fourth conductor. Advantageously, the third conductor is arranged at the proximal end of the first conductor and / or the proximal end of the second conductor. Advantageously, the fourth conductor is arranged at the distal end of the first conductor and / or the distal end of the second conductor.

[0028] For example, when the sintering device includes only the first (or second) conductor, the third conductor is disposed at the proximal end of the first (or second) conductor, and the fourth conductor is disposed at the distal end of the first (or second) conductor. For example, when the sintering device includes the first conductor and the second conductor, the third conductor is disposed at the proximal end of the first conductor and the proximal end of the second conductor, and the fourth conductor is disposed at the distal end of the first conductor and the distal end of the second conductor.

[0029] Advantageously, when the sintering apparatus comprises a third conductor and a fourth conductor arranged as explained above, the heating device comprises means for inducing a current to the third conductor and the fourth conductor. Advantageously, in use, when a current is induced to the third conductor and the fourth conductor, the current is induced to the first conductor and / or the second conductor and heats the third thermally conductive substrate and / or the fourth thermally conductive substrate.

[0030] Advantageously, the third conductor and the fourth conductor independently comprise copper, a copper alloy, silver, a silver alloy, tungsten, a tungsten alloy, or a combination of two or more thereof.

[0031] Alternatively or additionally, the heating means comprise means for inducing an electric current, and advantageously, the heating means further comprise an infrared (IR) light source.

[0032] Advantageously, when the heating means comprises an IR light source, the sintering apparatus further comprises one or more lenses.Advantageously, the lenses are arranged to allow, in use, the IR light beam to be focused onto the third conductive substrate and / or the fourth conductive substrate.

[0033] The heating device may be arranged to allow the third heat-conducting substrate and the fourth heat-conducting substrate to be heated independently of each other. For example, the heating device may be arranged to heat the third heat-conducting substrate and the fourth heat-conducting substrate according to the same heating curve in use, such as heating at the same heating rate and / or heating to the same temperature. Alternatively, the heating device may be arranged to heat the third heat-conducting substrate and the fourth heat-conducting substrate, for example to another temperature and / or at different heating rates in use.

[0034] Advantageously, the sintering device further comprises means for monitoring the temperature. Advantageously, the sintering device further comprises means for monitoring the temperature of the space between the first heat-conducting substrate and the second heat-conducting substrate. Alternatively or additionally, and advantageously, the sintering device further comprises means for monitoring the temperature of the third heat-conducting substrate and / or the fourth heat-conducting substrate. Advantageously, the means for controlling the temperature comprises an infrared (IR) camera.

[0035] An advantage of the sintering apparatus of the present invention is that heating with a high heating rate of at least 50°C / s can be obtained. Other advantages of the sintering apparatus of the present invention are, but not limited to, that various substrates can be sintered in a short time and in a uniform manner.

[0036] Furthermore, the sintering apparatus of the present invention is particularly suitable for sintering thin and / or substantially flat substrates, as well as self-supporting substrates. This is achieved by combining a third heat-conducting substrate and a fourth heat-conducting substrate, the third heat-conducting substrate and the fourth heat-conducting substrate comprising one or more metal nitrides and / or metal oxides and being heated, and the first heat-conducting substrate and the second heat-conducting substrate comprising carbon, placed between the substrate to be sintered (i.e., article or object) and the third heat-conducting substrate and the fourth heat-conducting substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Aspects of the present invention will now be described in more detail with reference to the accompanying drawings, in which like reference numerals illustrate like features, and in which:

[0038] Figures 1 to 11 Schematically showing various sintering apparatuses according to the present invention;

[0039] Fig. 12A and Fig. 12B SEM images of different resolutions showing a cross section of an inorganic substrate sintered by means of a prior art apparatus;

[0040] Fig.13A and Fig. 13B SEM images of different resolutions of a cross section of an inorganic substrate sintered by means of the sintering device of the present invention are shown. DETAILED DESCRIPTION

[0041] Figure 1 A sintering device 100 according to a first embodiment of the present disclosure is schematically shown. The sintering device 100 has a substantially horizontal arrangement. The device 100 comprises a first heat-conducting substrate 2 and a second heat-conducting substrate 3, which are arranged at a distance from each other so as to provide a space 101. In use of the device, an object to be sintered (e.g. an inorganic substrate) is advantageously placed in the space 101, i.e. between the first heat-conducting substrate 2 and the second heat-conducting substrate 3.

[0042] The first heat conducting substrate 2 and the second heat conducting substrate 3 are disposed between the third heat conducting substrate 4 and the fourth heat conducting substrate 5. In other words, the third heat conducting substrate 4 and the fourth heat conducting substrate 5 surround or enclose the first heat conducting substrate 2 and the second heat conducting substrate 3.

[0043] Advantageously, the first heat-conducting substrate 2 and the second heat-conducting substrate 3 independently of each other include carbon or consist essentially of it. Examples of carbon-containing heat-conducting substrates include, but are not limited to, graphite, carbon fibers, carbon nanotubes, or a combination of two or more thereof. The first heat-conducting substrate 2 and the second heat-conducting substrate 3 may have the same or different compositions. The first heat-conducting substrate 2 and the second heat-conducting substrate 3 may be substantially flat independently of each other. Alternatively, and independently of each other, they may have a geometry that follows the geometry of the object to be sintered. Advantageously, the first heat-conducting substrate 2 and the second heat-conducting substrate 3 independently of each other have a thickness between 0.5 μm and 20 mm, preferably between 1 μm and 10 mm.

[0044] The third thermally conductive substrate 4 and the fourth thermally conductive substrate 5 may have the same or different compositions. Advantageously, the third thermally conductive substrate 4 and the fourth thermally conductive substrate 5 include or consist substantially of a metal nitride or a metal oxide. Non-limiting examples of metal nitrides include boron nitride or aluminum nitride. Non-limiting examples of metal oxides include aluminum oxide or sapphire, such as a sapphire single crystal. Advantageously, the metal nitride includes or consists substantially of a single crystal metal nitride. Advantageously, the metal oxide includes or consists substantially of a single crystal metal oxide. The inventors have found that, compared to non-single crystal metal nitrides and metal oxides, single crystal metal nitrides and single crystal metal oxides are better able to resist the high heating rates (i.e., at least 50°C / s) and high cooling rates (i.e., at least -50°C / s) that can be achieved by the sintering equipment of the present disclosure, i.e., do not exhibit significant damage or degradation.

[0045] Advantageously, at least a portion of one or more surfaces, and preferably the entire surface, of the third heat conducting substrate 4 and / or the fourth heat conducting substrate 5 is polished.

[0046] The third heat conducting substrate 4 and the fourth heat conducting substrate 5 may be substantially flat independently of each other. Alternatively, and independently of each other, they may have a geometry that follows (i.e. matches) the geometry of the object to be sintered. Advantageously, the third heat conducting substrate 4 and the fourth heat conducting substrate 5 independently of each other have a thickness between 0.5 μm and 20 mm, preferably between 1 μm and 10 mm.

[0047] The inventors surprisingly found that by using the third thermally conductive substrate 4 and the fourth thermally conductive substrate 5 as explained above, it is possible to sinter the substrate while maintaining its original shape or geometry. In particular, the sintering apparatus of the present invention allows sintering a flat substrate even when it is thin (i.e., having a thickness of 100 μm or less), thereby maintaining its flatness during sintering. In other words, when a flat substrate is sintered by means of the sintering apparatus of the present disclosure, bending of the substrate is prevented.

[0048] Furthermore, the substrate to be sintered is provided with sufficient support, so that no supporting means, such as a tray, are required for the object during sintering. Thus, the sintering apparatus of the invention allows sintering of self-supporting substrates, such as self-supporting thin membranes.

[0049] The inventors surprisingly found that by using a first heat conductive substrate 2 and a second heat conductive substrate 3 (which comprises carbon and, in use of the apparatus, is arranged between the substrate to be sintered and the third heat conductive substrate 4 and the fourth heat conductive substrate 5), any solid-state reaction that may occur between the object to be sintered and the third heat conductive substrate 4 and the fourth heat conductive substrate 5 can be avoided. Such solid-state reactions usually negatively affect the sintering quality and are therefore unwanted reactions. Therefore, the sintering apparatus according to the present invention allows any such reactions to be avoided, thereby improving the sintering quality.

[0050] Figure 1 The sintering device 100 further comprises a first conductor 6 and a second conductor 7. Advantageously, the surface areas of the first conductor 6 and the second conductor 7 are equal to or greater than the surface areas of the third heat conducting substrate 4 and the fourth heat conducting substrate 5, respectively.

[0051] Advantageously, the first conductor 6 and the second conductor 7 individually comprise or consist essentially of carbon. Examples of carbon-containing conductors include, but are not limited to, graphite, carbon fibers, carbon nanotubes, or a combination of two or more thereof. Advantageously, the first conductor 6 and the second conductor 7 comprise or consist essentially of a carbon nonwoven material such as carbon felt.

[0052] The sintering apparatus 100 further comprises a heating device 102. The heating device is connected to the first conductor 6 and the second conductor 7. The connection may be any electrical connection known in the art and, in use, transfers current from the heating device 102 to the first conductor 6 and the second conductor 7, i.e., induces current to the conductors 6, 7. A power supply 103 is provided to generate the current. The power supply 103 may be a direct current (DC) power supply or an alternating current (AC) power supply.

[0053] In use, when the substrate to be sintered is arranged in the space 101 of the sintering device 100, the power supply 103 will generate a current which is induced to the first conductor 6 and the second conductor 7 by means of the heating device 102. The current will flow through the conductors 6, 7, and any losses due to the resistance of the material of the conductors 6, 7 are transferred in the form of heat. This heat results in heating the third heat-conducting substrate 4 and the fourth heat-conducting substrate 5, which in turn results in heating the first heat-conducting substrate 2 and the second heat-conducting substrate 3, and thus results in heating the substrate to be sintered.

[0054] The sintering apparatus allows to obtain a heating rate of 50°C / s or more, such as at least 60°C / s, or even 70°C / s or more, ie the sintering apparatus is an ultrafast sintering apparatus.

[0055] Advantageously, the sintering apparatus allows a cooling rate of 50°C / s or more to be obtained, i.e. cooling the item or object to a temperature at least 50°C lower than the temperature of the item or object a second ago, such as at least 60°C / s, or even 70°C / s or more.

[0056] Advantageously, the sintering device 100 further comprises means 104 for monitoring the temperature within the sintering device 100. Advantageously, the means 104 for monitoring the temperature comprises an IR sensor and / or an IR camera. Advantageously, the means 104 for monitoring the temperature allow measuring the temperature and controlling the temperature such that the temperature remains within a predefined value or within a predefined range.

[0057] The device 104 for monitoring temperature can be arranged so that it monitors the temperature in the space 101 (i.e., the object to be sintered) during sintering. Alternatively or additionally, the device 104 can be arranged to monitor the temperature of one or more of the first heat-conducting substrate 2, the second heat-conducting substrate 3, the third heat-conducting substrate 4, or the fourth heat-conducting substrate 5.

[0058] Advantageously, the sintering device further comprises cooling means (not shown). Advantageously, the cooling means allow cooling of the space, ie the sintered object, at a cooling rate of at least -50°C / s.

[0059] Advantageously, the sintering apparatus is arranged in a glove box (not shown) which is filled with an inert gas during use. In other words, the sintering apparatus is advantageously arranged for performing the sintering process in an inert atmosphere, such as an atmosphere comprising argon, nitrogen or helium.

[0060] The third heat-conducting substrate 4 can be arranged at a distance from the first heat-conducting substrate 2 and / or at a distance from the first conductor 6. Advantageously, each distance is individually between 0.05 mm and 25 mm, such as between 0.1 mm and 20 mm, between 0.2 mm and 15 mm, or between 0.25 mm and 10 mm. Alternatively, the third heat-conducting substrate 4 can at least partially contact, for example, can at least partially touch the first heat-conducting substrate 2, and / or can at least partially contact the first conductor 6.

[0061] The fourth heat-conducting substrate 5 may be arranged at a distance from the second heat-conducting substrate 3 and / or at a distance from the second conductor 7. Advantageously, each distance is individually between 0.05 mm and 25 mm, such as between 0.1 mm and 20 mm, between 0.2 mm and 15 mm, or between 0.25 mm and 10 mm. Alternatively, the fourth heat-conducting substrate 5 may at least partially contact, for example, may at least partially touch, the second heat-conducting substrate 3, and / or may at least partially contact the second conductor 7.

[0062] Figure 2A sintering device 110 is shown. Figure 1 In contrast to the sintering apparatus 100 of the present invention, the third heat conductive substrate 4 contacts the first heat conductive substrate 2 and the first conductor 6 over its entire surface area. In other words, the third heat conductive substrate 4 is sandwiched between the first heat conductive substrate 2 and the first conductor 6. In addition, the fourth heat conductive substrate 5 also contacts the second heat conductive substrate 3 and the second conductor 7 over its entire surface area.

[0063] Optionally, the first conductor 6 at least partially surrounds the third heat-conducting substrate 4 (not shown). In addition, and still optionally, the first conductor 6 may also at least partially surround the first heat-conducting substrate 2, the space 101, and even the second heat-conducting substrate 3 and the fourth heat-conducting substrate 5. Similarly and optionally, the second conductor 7 at least partially surrounds the fourth heat-conducting substrate 5 (not shown). In addition, and still optionally, the second conductor 7 may also at least partially surround the second heat-conducting substrate 3, the space 101, and even the first heat-conducting substrate 2 and the third heat-conducting substrate 4.

[0064] In other words, the first conductor 6 and / or the second conductor 7 may be a covering (eg a wrap or envelope) surrounding the space 101 and the thermally conductive substrate 2, 3, 4, 5, while still providing an opening so that the substrate to be sintered may be arranged in the space.

[0065] An advantage of the first conductor 6 and / or the second conductor 7 at least partially surrounding one or more of the thermally conductive substrates 2, 3, 4, 5 and optionally the space 101 is that a more uniform and / or higher heating rate may be obtained.

[0066] Figure 3 FIG. 1 shows a sintering device 120 according to another embodiment of the present invention. Figure 2 As disclosed in , the sintering apparatus 120 includes first, second, third, and fourth heat conductive substrates 2, 3, 4, and 5, and first and second conductors 6 and 7, such that a space 101 is provided between the first and second heat conductive substrates 2 and 3.

[0067] The sintering apparatus 120 further comprises a first heating device 102a connected to the second conductor 7 and the first power source 103a. The sintering apparatus 120 further comprises a second heating device 102b connected to the first conductor 6 and the second power source 103b. The power sources 103a, 103b may be as described above.

[0068] The first heating device 102a is arranged to induce, in use, a current into the second conductor 7. The second heating device 102b is arranged to induce, in use, a current into the first conductor 6. When a current is induced into the conductors 6, 7, the adjacent heat-conducting substrates 5, 4 are heated. As a result, the heat-conducting substrates 3, 2 adjacent to the heated heat-conducting substrates 5, 4 are also heated, resulting in heating and sintering of the object to be sintered.

[0069] The separate heating devices 102a, 102b that are each connected to different conductors 7, 6 are provided with the following advantages: different amounts or levels of current can be induced to the corresponding conductors. In other words, the first heating device 102a and the second heating device 102b are arranged so that advantageously, the fourth heat-conducting substrate 5 and the second heat-conducting substrate 3 and the third heat-conducting substrate 4 and the first heat-conducting substrate 2 can be heated to different temperatures at different heating rates and / or in different durations (i.e., different sintering times), respectively. This allows obtaining a sintered substrate, which, for example, has a first porosity at a first surface and a second porosity at a second surface (such as a surface opposite to the first surface) that is different from the first porosity. For example, a substrate having a porosity gradient over its entire thickness can be obtained. This is because different sintering temperatures and / or different sintering durations often result in obtaining different (i.e., lower or higher) porosities. For example, a double-layer dense porous substrate can be obtained by a single substrate in this way.

[0070] Figure 4 Other embodiments of the sintering apparatus 130 of the present invention are disclosed. Figure 2 As disclosed in , the sintering device 130 includes a first heat conductive substrate 2 , a second heat conductive substrate 3 , a third heat conductive substrate 4 , and a fourth heat conductive substrate 5 , as well as a first conductor 6 and a second conductor 7 .

[0071] The sintering device 130 further comprises a third conductor 8 and a fourth conductor 9. Advantageously, the electrical conductivity of the third conductor 8 and the fourth conductor 9 is within 10 -3 S / cm to 75*10 4 Advantageously, the third conductor 8 and the fourth conductor 9 independently comprise copper, copper alloy, silver, silver alloy, tungsten, tungsten alloy, iron, iron alloy or a combination of two or more thereof.

[0072] Advantageously, the third conductor 8 is arranged at the proximal end 60 of the first conductor 6 and at the proximal end 70 of the second conductor. Advantageously, the third conductor 8 at least partially, and preferably completely contacts the first conductor 6 at the proximal end 60 of the first conductor 6, and / or at least partially, and preferably completely contacts the second conductor 7 at the proximal end 70 of the second conductor 7.

[0073] Advantageously, the fourth conductor 9 is arranged at the distal end 61 of the first conductor 6 and the distal end 71 of the second conductor. Advantageously, the fourth conductor 9 at least partially, and preferably completely contacts the first conductor 6 at the distal end 61 of the first conductor 6, and / or at least partially, and preferably completely contacts the second conductor 7 at the distal end 71 of the second conductor 7.

[0074] Advantageously, the heating device 102 is connected to the third and fourth conductors 8, 9 and to a power source 103. Thereby, in use, current may be induced to the third and fourth conductors 8, 9 and thereby to the first and second conductors 6, 7, thereby heating the substrate to be sintered as described above.

[0075] Figure 5 Another embodiment of the sintering apparatus 140 of the present invention is disclosed. Figure 2 As disclosed in , the sintering device 140 includes a first heat conductive substrate 2 , a second heat conductive substrate 3 , a third heat conductive substrate 4 , and a fourth heat conductive substrate 5 , as well as a first conductor 6 and a second conductor 7 .

[0076] The sintering device 140 further includes a third conductor, which includes a first portion 81 and a second portion 82. The sintering device 140 further includes a fourth conductor, which includes a first portion 91 and a second portion 92. Advantageously, the electrical conductivity of the third conductor and the fourth conductor is within 10 -3 S / cm to 75*10 4 Advantageously, the third conductor and the fourth conductor independently comprise copper, copper alloy, silver, silver alloy, tungsten, tungsten alloy, iron, iron alloy or a combination of two or more thereof.

[0077] Advantageously, the first portion 81 of the third conductor is arranged at the proximal end 60 of the first conductor 6, and in particular at least partially contacts the proximal end 60 of the first conductor 6. Advantageously, the first portion 91 of the fourth conductor is arranged at the distal end 61 of the first conductor 6, and in particular at least partially contacts the distal end 61 of the first conductor 6. The second heating device 102b is connected to the first portion 81, 91 and the second power supply 103b. The second heating device 102b is arranged to induce a current to the first portion 81, 91 in use, and in this way to the first conductor 6. This results in Joule heating of the third heat conducting substrate 4 and the first heat conducting substrate 2, as explained above.

[0078] Advantageously, the second portion 82 of the third conductor is arranged at the proximal end 70 of the second conductor 7, and in particular at least partially contacts the proximal end 70 of the second conductor 7. Advantageously, the second portion 92 of the fourth conductor is arranged at the distal end 71 of the second conductor 7, and in particular at least partially contacts the distal end 71 of the second conductor 7. The first heating device 102a is connected to the second portion 82, 92 and the first power supply 103a. The first heating device 102a is arranged to induce a current to the second portion 82, 92 in use, and in this way to the second conductor 7. This results in Joule heating of the fourth heat conducting substrate 5 and the second heat conducting substrate 3, as explained above.

[0079] Figure 6A sintering device 150 according to another embodiment of the present disclosure is disclosed. Figure 2 As disclosed in , the sintering apparatus 150 includes a first heat conductive substrate 2 , a second heat conductive substrate 3 , a third heat conductive substrate 4 and a fourth heat conductive substrate 5 , a first conductor 6 and a second conductor 7 , a heating device 102 and a power supply 103 .

[0080] The sintering device 150 further comprises a first supporting device and a second supporting device. Advantageously, the first supporting device is arranged at the outer surface of the first conductor 6, that is, the first conductor 6 is oriented toward the third heat-conducting substrate 4 (that is, oriented toward the third heat-conducting substrate 4 (or at Figure 6 In the case of the second conductor 7, the second support means is arranged at the side opposite to the side of the third heat conducting substrate 4). Advantageously, the second support means is arranged at the outer surface of the second conductor 7.

[0081] Advantageously, each support means comprises a ceramic substrate 105. Advantageously, the ceramic substrate 105 is thermally and / or electrically insulating, preferably thermally and electrically insulating. Advantageously, the ceramic substrate 105 comprises or consists essentially of aluminium oxide.

[0082] Advantageously, each support device further comprises at least one metal support component 106, preferably at least 2, more preferably at least 3, i.e., a plurality of metal support components 106. Advantageously, the metal support component 106 comprises or substantially consists of one or more metals and / or alloys thereof capable of withstanding the sintering temperature. In particular, the metal support component 106 comprises or substantially consists of one or more metals and / or alloys thereof having a melting temperature of at least 1500° C. (e.g., at least 1750° C. or at least 2000° C.) so as to avoid melting of the metal support component 106 during heating and sintering.

[0083] Advantageously, the metal support member 106 includes or consists essentially of tungsten or an alloy thereof. Non-limiting examples of tungsten-containing alloys are tungsten-nickel-iron alloys, tungsten-nickel-copper alloys, and tungsten carbide alloys.

[0084] The metal support member 106 may have any shape that allows the metal support member 106 to be arranged between the ceramic substrate 105 and the (first or second) conductor 6, 7 so that the metal support member 106 contacts both the ceramic substrate 105 and the conductor 6, 7. Non-limiting examples of shapes include cylinders, cubes, pyramid shapes, and spheres. Non-limiting practical examples of structures include needles, rods, and cylinders.

[0085] Advantageously, the metal support member 106 is attached to the ceramic substrate 105 . The attachment may be any type of attachment known in the art. Advantageously, the metal support member 106 is embedded in the ceramic substrate 105 .

[0086] When in contact, the support device provides mechanical support for the conductor and therefore also for the thermally conductive substrate. In use of the sintering device 150, the support device mechanically supports the substrate to be sintered in this way. This eliminates the need to arrange the substrate to be sintered and the carrier or support structure in the space 101. In other words, the sintering device 150 including the support device allows the sintering of a self-supporting substrate.

[0087] Figure 7 A sintering device 160 according to another embodiment of the present disclosure is disclosed. Figure 4 As disclosed in , the sintering device 160 includes a first heat conductive substrate 2, a second heat conductive substrate 3, a third heat conductive substrate 4 and a fourth heat conductive substrate 5 and a first conductor 6, a second conductor 7, a third conductor 8 and a fourth conductor 9. Figure 6 As disclosed in , the sintering device 160 further includes a first supporting device and a second supporting device.

[0088] Figure 8 A sintering device 170 according to another embodiment of the present disclosure is disclosed. Figure 3 As disclosed in , the sintering device 170 includes a first heat conductive substrate 2, a second heat conductive substrate 3, a third heat conductive substrate 4 and a fourth heat conductive substrate 5, a first conductor 6 and a second conductor 7, a first heating device 102a and a second heating device 102b, and a first power supply 103a and a second power supply 103b. Figure 6 As disclosed in , the sintering device 170 further includes a first supporting device and a second supporting device.

[0089] The sintering apparatus of the present invention may be arranged in a substantially horizontal configuration, i.e. at an angle of 90° to the earth's gravitational field (shown in FIG. Figures 1 to 8 The sintering device can also be arranged in a substantially vertical position, i.e., at an angle of 0° to the earth's gravitational field, such as Fig. 9 The sintering apparatus may also be arranged in any position between a substantially horizontal position (ie, an angle of 90°) and a substantially vertical position (ie, an angle of 0°).

[0090] Fig. 9 A sintering apparatus 180 is shown, which is similar to Figure 6 The sintering apparatus 150 is similar to the sintering apparatus 150 of the present invention, but arranged in a vertical position (at an angle of 0° to the earth's gravitational field). The inventors have found that the vertical position allows easier movement of particles within the object or substrate to be sintered during sintering due to gravity. Such a vertical setup is particularly advantageous for sintering flat substrates such as films, foils and diaphragms.

[0091] Fig.10A sintering device 190 according to a further embodiment is shown. The sintering device 190 comprises a first heat conducting substrate 2 contacting a third heat conducting substrate 4, and a second heat conducting substrate 3 contacting a fourth heat conducting substrate 5. The heat conducting substrates 2, 3, 4, 5 are advantageously as described above. The sintering device 190 further comprises a device 104 for monitoring the temperature, which is advantageously as described above.

[0092] The sintering device 190 also includes a heating device 10, which includes a light source. Advantageously, the light source is an infrared (IR) light source. The IR light source advantageously includes one or more IR heaters. Particularly suitable IR heaters are short-wave IR heaters and ceramic IR heaters. Advantageously, the IR heater is operated at a power of 6kW or less. Advantageously, the IR light source is operated at a temperature between 500°C and 1300°C, preferably between 600°C and 1000°C, most preferably between 650°C and 800°C (such as between 700°C and 750°C). Advantageously, the IR light source is turned on, that is, the IR light source heats the space between the thermally conductive substrate 2, 3, 4, 5 and / or the first thermally conductive substrate 2 and the second thermally conductive substrate 3f for a duration of between 5 seconds and 40 minutes, preferably between 10 seconds and 30 minutes (for example, between 1 minute and 25 minutes, between 2 minutes and 20 minutes, between 5 minutes and 15 minutes, more preferably between 7 minutes and 10 minutes (such as between 9 minutes and 10 minutes)). It will be appreciated that the optimum duration depends on the IR light source, in particular its power.

[0093] The sintering device 190 further comprises a lens 11 arranged between the light source 10 and the heat-conducting substrates 2, 3, 4, 5. Advantageously, the lens 11 is arranged to focus the light beam, in particular the IR light beam, emitted from the light source, onto the heat-conducting substrates 2, 3, 4, 5 and / or onto the space between the first heat-conducting substrate 2 and the second heat-conducting substrate 3 in use. This allows reducing energy (heat) losses and achieving a more efficient sintering device.

[0094] Fig.11 A sintering device 200 according to a further embodiment is shown. The sintering device 200 comprises a first heat-conducting substrate 2 in contact with a third heat-conducting substrate 4, and a second heat-conducting substrate 3 in contact with a fourth heat-conducting substrate 5. The heat-conducting substrates 2, 3, 4, 5 are advantageously as described above. The sintering device 200 further comprises a first conductor 6 and a second conductor 7, which are advantageously as described above and contact the third heat-conducting substrate 4 and the fourth heat-conducting substrate 5, respectively.

[0095] The sintering apparatus 200 further comprises first and second supporting means comprising a ceramic substrate 105 and at least one metallic supporting member 106. The first and second supporting means are advantageously as described above.

[0096] The sintering apparatus 200 further comprises an IR light source 10. The IR light source 10 is arranged such that, in use, the emitted IR light heats the conductors 6, 7 and the thermally conductive substrates 2, 3, 4, 5 and such that also the substrate to be sintered is heated.

[0097] Example

[0098] Example 1

[0099] The reference porous substrate and the inventive porous substrate were made of green structures having the same composition, wherein the reference porous substrate was obtained by sintering with the aid of a prior art sintering apparatus, while the inventive porous substrate was obtained by sintering with the aid of a sintering apparatus according to the invention.

[0100] First, a mixture was prepared by mixing 3 g of Li 6.25 Al 0.25 La3Zr2O 12 (aluminum-doped LLZO or Al-LLZO), 0.075gLi2CO3 (2.5wt%), 0.56mL plasticizer, 0.59g surfactant and 2.07g poly(methyl methacrylate) (PMMA) as a pore-forming compound and 5.9mL solvent (including 5vol.% isopropanol, 87vol.% ethanol and 8vol.% 1-propanol; then, ball milling was performed at a rotation speed of 165rpm for 18 hours. A binder solution was prepared by adding 3g polyvinyl butyral to 8.89mL isopropanol. 2.51g of the binder solution was added to the mixture (suspension), and then further ball milling was performed at a rotation speed of 200rpm for 2 hours.

[0101] The mixture film was tape cast on a glass substrate. This operation was performed twice to obtain two green structures (i.e., one for each sintering method). The obtained green structures were kept at ambient conditions for 1 hour to allow the solvent to evaporate, and then the green structures were removed from the glass substrate.

[0102] The green structure was then placed between two alumina plates. Debinding of the green structure was performed in air at 600°C to completely remove the solvent (evaporation temperature up to 150°C), PMMA (about 350°C) and residual organic compounds such as binders and plasticizers (about 600°C).

[0103] A reference (sintered) LLZO substrate was obtained by placing the first green structure between two carbon foils, which were then sandwiched between two carbon plates. Sintering was performed at 1250° C. for 30 seconds in a nitrogen atmosphere.

[0104] SEM image of the cross section of the reference sintered LLZO substrate obtained ( Fig. 12Aand Fig. 12B , different magnifications) clearly show that the reference sintered LLZO substrate thus obtained is not flat but highly curved. Some cracks are also noted. SEM images were recorded using a Hitachi TM3030Plus desktop microscope with an accelerating voltage of 10 kV.

[0105] Similar results were also obtained by sintering in the same equipment in a nitrogen atmosphere at a temperature between 1000° C. and 1250° C. for a duration between 30 seconds and 120 seconds.

[0106] By placing a second green structure having the same composition as the first green structure in a Figure 7 In the device 160, the (sintered) LLZO substrate of the present invention is obtained.

[0107] The first heat conducting substrate 2 and the second heat conducting substrate 3 are substantially composed of carbon foil. The third heat conducting substrate 4 and the fourth heat conducting substrate 5 are boron nitride plates. The boron nitride plate is rigid and substantially flat. The first conductor 6 and the second conductor 7 are substantially composed of carbon and are carbon felt. Externally, a support device is provided, including an aluminum oxide substrate 105 and a plurality of tungsten needles as a metal support member 106. A copper third conductor 8 is provided at the proximal end of the first conductor 6 and the second conductor 7, and a copper fourth conductor 9 is provided at the distal end of the first conductor 6 and the second conductor 7. The third conductor 8 and the fourth conductor 9 are connected to a power supply 103 as a heating device by means of an electronic circuit system 102.

[0108] After placing the second green structure between the carbon foils 2, 3, the power supply 103 is turned on and an electric current is induced to and flows through the carbon felt. The resistive loss of the electric current results in heating of the boron nitride plate, which in turn heats the carbon foil and the green structure to a temperature of 1250°C at a heating rate of about 60°C / s. Once the temperature of 1250°C is reached, it is maintained for 30 seconds by a continuous current through the carbon felt.

[0109] The obtained cross-sectional SEM image of the sintered LLZO substrate of the present invention ( Fig.13A and Fig. 13B , different magnifications) clearly show that the sintered LLZO substrate of the present invention is substantially flat. Similar results were also obtained by sintering at a temperature between 1000° C. and 1250° C. for a duration between 30 seconds and 120 seconds under the same equipment and setup.

[0110] Example 2

[0111] Another green body structure according to Example 1 is Fig.10The first heat-conducting substrate 2 and the second heat-conducting substrate 3 are substantially composed of carbon foil. The third heat-conducting substrate 4 and the fourth heat-conducting substrate 5 are boron nitride plates. The boron nitride plates are rigid and substantially flat.

[0112] The green structure was placed between the carbon foils 2, 3. An IR light source including an IR heater operated at a power of 6 kW was used as a heating device. The IR radiation heated the boron nitride plates 4, 5 via thermal radiation, and the heat was transferred to the carbon foils 2, 3 and the green structure. The boron nitride plates 4, 5 were heated to a temperature of 700°C for a duration of 550 seconds. Afterwards, the IR light source was turned off, and the boron nitride plates, carbon foils and sintered LLZO substrates were allowed to cool to room temperature.

[0113] The resulting sintered LLZO substrate was visually inspected and found to be generally flat.

[0114] Reference numerals list

[0115] 2. First thermally conductive substrate

[0116] 3. Second thermally conductive substrate

[0117] 4. The third thermally conductive substrate

[0118] 5. Fourth thermal conductive substrate

[0119] 6. First conductor

[0120] 7. Second conductor

[0121] 8. Third conductor

[0122] 9. The fourth conductor

[0123] 10. Infrared (IR) light source

[0124] 11. Lens

[0125] 60. Proximal end of first conductor

[0126] 61. Distal end of first conductor

[0127] 70. Proximal end of the second conductor

[0128] 71. Distal end of the second conductor

[0129] 81. Third conductor (first part)

[0130] 82. The third conductor (part 2)

[0131] 91. Fourth conductor (first part)

[0132] 92. The fourth conductor (part 2)

[0133] 100. Equipment for sintering

[0134] 101. Space between the first heat-conducting substrate and the second heat-conducting substrate

[0135] 102. Device for inducing current

[0136] 102a. Device for inducing current

[0137] 102b. Device for inducing current

[0138] 103. Power supply

[0139] 103a. Power supply

[0140] 103b. Power supply

[0141] 104. Device for monitoring temperature

[0142] 105. Thermally and electrically insulating ceramic substrate

[0143] 106.Metal support parts

[0144] 110.Sintering equipment

[0145] 120.Sintering equipment

[0146] 130.Sintering equipment

[0147] 140.Sintering equipment

[0148] 150.Sintering equipment

[0149] 160.Sintering equipment

[0150] 170.Sintering equipment

[0151] 180.Sintering equipment

[0152] 190.Sintering equipment

[0153] 200. Sintering equipment.

Claims

1. An ultrafast high temperature sintering device (100, 110, 120, 130, 140, 150, 160, 170, 180, 190), comprising: - a first heat-conducting substrate (2) and a second heat-conducting substrate (3), the first heat-conducting substrate (2) and the second heat-conducting substrate (3) being arranged at a distance from each other so as to provide a space (101) for receiving a substrate to be sintered, and being arranged - between the third heat conducting substrate (4) and the fourth heat conducting substrate (5), and - a heating device (10, 102, 102a, 102b), the heating device (10, 102, 102a, 102b) being used to heat the third heat-conducting substrate (4) and / or the fourth heat-conducting substrate (5), thereby heating the first heat-conducting substrate (2) and / or the second heat-conducting substrate (3), respectively, wherein the first heat-conducting substrate (2) and the second heat-conducting substrate (3) comprise carbon, It is characterized in that the third heat-conducting substrate (4) and the fourth heat-conducting substrate (5) independently comprise one or more metal nitrides and / or metal oxides.

2. The sintering device (100, 110, 120, 130, 140, 150, 160, 170, 180, 190) according to claim 1, wherein the third heat conductive substrate (4) and the fourth heat conductive substrate (5) independently comprise one or more single-crystalline metal nitrides and / or single-crystalline metal oxides.

3. The sintering apparatus (100, 110, 120, 130, 140, 150, 160, 170, 180, 190) according to any of the preceding claims, wherein the metal nitride comprises boron nitride and / or aluminum nitride.

4. The sintering apparatus (100, 110, 120, 130, 140, 150, 160, 170, 180, 190) according to any of the preceding claims, wherein the metal oxide comprises aluminum oxide and / or sapphire.

5. The sintering apparatus (110, 120, 130, 140, 150, 160, 170, 180, 190) according to claim 1, wherein the first heat conductive substrate (2) at least partially contacts the third heat conductive substrate (4), and / or the second heat conductive substrate (3) at least partially contacts the fourth heat conductive substrate (5).

6. The sintering device (100, 110, 120, 130, 140, 150, 160, 170, 190) according to any of the preceding claims, further comprising a first conductor (6) at the outer surface of the third heat-conducting substrate (4) and / or a second conductor (7) at the outer surface of the fourth heat-conducting substrate (5), preferably wherein the first conductor (6) and the second conductor (7) comprise carbon.

7. The sintering device (100, 110, 120, 130, 140, 150, 160, 170, 190) according to claim 6, wherein the first conductor (6) and the second conductor (7) together at least partially, and preferably completely, surround the first heat conductive substrate (2), the second heat conductive substrate (3), the third heat conductive substrate (4), the fourth heat conductive substrate (5) and the space (101).

8. The sintering device (150, 160, 170, 190) according to any one of claims 6 to 7, further comprising a first supporting device arranged at the outer surface of the first conductor (6) and / or a second supporting device arranged at the outer surface of the second conductor (7), wherein each of the first supporting device and the second supporting device independently comprises a thermally insulating and electrically insulating ceramic substrate (105) and at least one metal supporting component (106), wherein the supporting device is arranged so that the metal supporting component (106) contacts the thermally insulating and electrically insulating ceramic substrate (105) and the conductors (6, 7).

9. The sintering apparatus (150, 160, 170, 190) of claim 8, wherein the thermally and electrically insulating ceramic substrate (105) comprises aluminum oxide.

10. The sintering apparatus (150, 160, 170, 190) according to any one of claims 8 to 9, wherein the metal support member (106) comprises tungsten or an alloy thereof.

11. A sintering apparatus (100, 110, 120, 130, 140, 150, 160, 170) according to any one of claims 6 to 10, wherein the heating device (102, 102a, 102b) comprises a device for inducing an electric current to the first conductor (6) and / or the second conductor (7), thereby, in use, heating the third heat-conducting substrate (4) and / or the fourth heat-conducting substrate (5).

12. The sintering device (130, 140) according to any one of claims 6 to 11, further comprising a third conductor (8, 81, 82) at the proximal end (60) of the first conductor (6) and / or at the proximal end (70) of the second conductor (7), and a fourth conductor (9, 91, 92) at the distal end (61) of the first conductor (6) and / or at the distal end (71) of the second conductor (7), wherein the heating device (102 , 102a, 102b) comprises means for inducing current to the third conductor (8, 81, 82) and the fourth conductor (9, 91, 92), so that, in use, current is induced to the first conductor (6) and / or the second conductor (7) respectively and the third heat-conducting substrate (4) and / or the fourth heat-conducting substrate (5) is heated, preferably wherein the third conductor (8, 81, 82) and the fourth conductor (9, 91, 92) comprise copper, tungsten or a combination thereof.

13. The sintering apparatus (180, 190) according to any one of claims 1 to 8, wherein the heating device (10) comprises an infrared (IR) light source.

14. The sintering apparatus (180, 190) according to claim 13, further comprising one or more lenses (11).

15. Sintering apparatus (120, 140, 160) according to any one of the preceding claims, wherein the heating means (10, 102a, 102b) is arranged to allow heating of the third heat conducting substrate (4) and the fourth heat conducting substrate (5) independently of each other in use.

16. The sintering device (100, 110, 120, 130, 140, 150, 160, 170, 180, 190) according to any one of the preceding claims, further comprising a device (104) for monitoring the temperature of the space (101) between the first heat conductive substrate (2) and the second heat conductive substrate (3), preferably wherein the device (104) for monitoring the temperature comprises an infrared (IR) camera.

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