Split type tungsten isolation tool and sintering method of large-size transparent ceramic

Abstract

The invention discloses a split type tungsten isolation tool and a sintering method of large-size transparent ceramic, and belongs to the field of ceramic sintering, the split type tungsten isolation tool comprises a tungsten bottom plate, two tungsten long side plates, two tungsten short side plates and a tungsten cover plate, the two tungsten long side plates and the two tungsten short side plates define a tungsten boat peripheral frame body, the adjacent tungsten long side plates and tungsten short side plates are connected through tungsten connecting plates, and the tungsten connecting plates are connected with the tungsten long side plates and the tungsten short side plates. A material cavity is formed in the frame around the tungsten boat, the face, facing the material cavity, of the tungsten cover plate is connected with a tungsten reinforcing rib set used for preventing the cover plate from collapsing, and the tungsten cover plate covers the frame around the tungsten boat. The density of the sintered large-size ceramic is greater than or equal to 99%, and the visible light transmittance is greater than or equal to 78%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ceramic sintering, in particular to a split type tungsten isolation tool and a sintering method of large-size transparent ceramic. BACKGROUND

[0002] At present, large-size transparent ceramic (such as lanthanum zirconate gadolinium ceramic, typically requiring a diameter of 100 mm or more, a thickness of 5 mm or more, or an effective size of 380*550*60 mm) has a significant application demand in the field of optical devices, high-temperature observation windows, and key components of new energy fields. The performance of such ceramic (especially visible light transmittance and density) is highly dependent on the sintering process, and graphite vacuum furnace becomes the core equipment for sintering large-size transparent ceramic due to its ability to stably provide a high-temperature environment of 2000℃ and strong controllability of atmosphere. However, graphite furnace body is prone to release carbon elements at high temperature, which will cause carbon contamination if directly contacting the sample. Therefore, "carbon contamination isolation", "process adaptability", and "tool durability" have become the core direction of the industry.

[0003] In terms of tooling, to avoid the penetration of carbon elements in the graphite furnace into the ceramic sample, the industry generally uses tungsten, tantalum, and molybdenum refractory metals to make sample isolation tools (such as crucibles and sealed boxes).

[0004] Molybdenum: The melting point of molybdenum is about 2620℃, and its cost is lower than that of tungsten and tantalum. It is cost-effective in medium-temperature sintering scenarios below 1800℃, and is often used as an isolation carrier for small and medium-sized ceramic samples. However, molybdenum is limited by material properties. It is at the limit of resistance in a 2000℃ vacuum environment, and is prone to embrittlement due to recrystallization effect during long-term use (such as holding for more than 600 minutes), resulting in short tool life and inability to meet the core needs of long-time high-temperature sintering of large-size transparent ceramic.

[0005] Tantalum: The melting point of tantalum is about 2996℃, and it has excellent high-temperature strength and good processing performance. It is often used as a heating element in high-vacuum small furnaces (such as high-vacuum tantalum heating furnaces), and its working temperature can reach 1800℃. However, the price of tantalum raw materials is high, and the cost of making isolation tools for large-size ceramic is extremely high. Moreover, tantalum still has oxidation risk at high temperature, which makes it economically unfeasible for large-scale application.

[0006] Tungsten: The melting point of tungsten is about 3410℃, making it the most heat-resistant material among metals. It has strong stability, low vapor pressure, and resistance to volatilization in a 2000℃ vacuum environment, which can effectively isolate carbon contamination, making it an ideal isolation material for high-temperature sintering of large-size transparent ceramic. However, the existing design of tungsten isolation tools for large-size transparent ceramic (such as tungsten boxes and tungsten crucibles) has obvious defects, making it difficult to balance "sealing, durability, and economy". The performance is as follows: (1) Unreasonable structure: mostly integrated processing, while tungsten material is brittle at room temperature and difficult to process. Once the local tooling is damaged (such as bottom plate wear, frame corner cracking), it needs to be replaced as a whole, and the replacement cost is more than 80% of the whole tooling.

[0007] (2) Design deficiency in key positions: the bottom plate thickness is generally less than 15mm, which is easy to deform and crack after long-term bearing sample weight and high temperature impact, and the service life is usually less than 10 sintering cycles; the frame is mostly welded and fixed, which is easy to crack at high temperature due to thermal expansion, resulting in decreased sealing performance and increased risk of carbon contamination; the top plate is easy to collapse at high temperature due to its own weight or thermal stress, which may press the sample or damage the isolation environment, and the rate of downward collapse is more than 30%.

[0008] (3) High processing difficulty and poor universality of large-size tooling: the integrated tungsten box has extremely high processing difficulty due to its large size (such as 380*550*60mm), and the qualified rate is less than 60%; and the tooling size is fixed, which cannot be adapted to different specifications of large-size ceramic samples (such as two different toolings for 100mm and 150mm diameter samples), resulting in poor universality and increased use cost.

[0009] In terms of sintering process, the current industry mostly uses traditional solid phase method to synthesize ceramic powder (the powder preparation cost of this method is relatively low, and the technical threshold is relatively low), but the sintering process parameters are not suitable for the characteristics of large-size samples, such as slow heat conduction and difficult densification, which are as follows: (1) Insufficient vacuum control: the vacuum degree of the high-temperature sintering section (1600℃~2000℃) is mostly maintained at 1×10 -2 Pa level, which cannot efficiently discharge the pores generated in the sintering process inside the ceramic, and the residual pores will directly lead to the decrease of ceramic density, and then affect the visible light transmittance.

[0010] (2) Unreasonable heating and holding logic: lack of stepwise heating design, and insufficient holding time at high temperature (usually less than 400min). Due to the low heat conduction efficiency of large-size samples, the internal and external temperature difference is easy to exceed 50℃, leading to uneven sintering, abnormal grain growth or insufficient densification in some areas, finally resulting in ceramic density less than 95%, and visible light transmittance mostly less than 70%, which cannot meet the needs of high-end optical scenes.

[0011] The above background technology is for the convenience of understanding the present application, and is not the known technology publicly disclosed to the public before the present application. SUMMARY

[0012] In view of the above defects, the present application provides a split tungsten isolation tooling, which aims to improve at least one problem mentioned in the background technology.

[0013] The technical scheme is: a split type tungsten isolation tool, comprising a tungsten bottom plate, two tungsten long side plates, two tungsten short side plates and a tungsten cover plate, the two tungsten long side plates and the two tungsten short side plates surround a tungsten boat four-around frame, adjacent tungsten long side plates and tungsten short side plates are connected through a tungsten connecting plate, the tungsten boat four-around frame is a material cavity, the tungsten cover plate is connected with a tungsten reinforcing rib group for preventing the cover plate from collapsing on one side facing the material cavity, and the tungsten cover plate covers the tungsten boat four-around frame.

[0014] Further, the thickness of the tungsten bottom plate is 18mm, and the thickness of the tungsten cover plate is 5mm.

[0015] Further, the tungsten connecting plate comprises a first connecting part and a second connecting part, the included angle between the first connecting part and the second connecting part is a right angle, the first connecting part and the second connecting part are both provided with a connecting plate through hole, the two tungsten long side plates and the two tungsten short side plates are both provided with a side plate through hole, a first tungsten connecting piece is connected between each connecting plate through hole and the side plate through hole matched therewith, and the first tungsten connecting piece comprises a tungsten screw and a tungsten nut.

[0016] Further, the tungsten reinforcing rib group comprises one tungsten long reinforcing rib and two tungsten short reinforcing ribs, the tungsten long reinforcing rib is connected on one diagonal line of the tungsten cover plate, and the two tungsten short reinforcing ribs are connected on the other diagonal line of the tungsten cover plate.

[0017] Further, the tungsten cover plate is provided with a cover plate through hole on the diagonal line, the tungsten long reinforcing rib and the tungsten short reinforcing rib are both provided with a reinforcing rib through hole, a second tungsten connecting piece is connected between each cover plate through hole and the reinforcing rib through hole matched therewith, and the second tungsten connecting piece comprises a tungsten screw and a tungsten nut.

[0018] Further, the tungsten bottom plate is provided with a boss, and the bottom of the tungsten boat four-around frame is sleeved on the boss.

[0019] The application also provides a sintering method of large-size transparent ceramic.

[0020] The technical scheme is: a sintering method of large-size transparent ceramic, comprising the following steps: S1, taking a green body and placing it into the material cavity of the split type tungsten isolation tool according to any one of claims 1-6, and then placing the split type tungsten isolation tool into a graphite vacuum furnace; S2, sintering: S21, low-temperature preheating stage, parameters: 1*10 -2 Pa, rising to a sintering critical point within 300 min; S22, medium-temperature transition stage, parameters: 1*10 -2 Pa, keeping at the sintering critical point for 120 min; S23, high-temperature rising stage: S231, first section of the high-temperature rising stage, parameters: 1*10-2 Pa, 1600℃ for 120min; S232, the second section of the high-temperature heating stage, parameters: 6*10 -3 Pa, 1600℃ for 120min; S233, the third section of the high-temperature heating stage, parameters: 6*10 -3 Pa, 1000min to 1850℃; S24, the high-temperature holding stage, parameters: 6*10 -3 Pa, 1850℃ for 1080min; S25, the slow cooling stage, parameters: 6*10 -3 Pa, 325min to 1200℃, then 175min to 500℃, and then natural cooling.

[0021] Further, the effective size of the split tungsten isolation tool is 380*550*60mm.

[0022] Further, in S1, the assembly of the split tungsten isolation tool and the green body feeding, comprising the following steps: M1, connecting the tungsten connecting plate to the two tungsten long side plates and the two tungsten short side plates by tungsten screws and tungsten nuts to form a frame around the tungsten boat; connecting the tungsten long reinforcing ribs and the tungsten short reinforcing ribs to the tungsten cover plate by tungsten screws and tungsten nuts to form a cover plate with reinforcing ribs; M2, pressing the frame around the tungsten boat downward on the boss of the tungsten bottom plate; M3, placing the green body into the cavity and covering the cover plate with reinforcing ribs.

[0023] Further, the large-size transparent ceramic is lanthanum gadolinium zirconate ceramic with a diameter of 100mm and a thickness of 5mm.

[0024] Compared with the prior art, the present application has the following beneficial effects: The present application designs a spliced / split tungsten box (composed of a bottom plate, a frame, and a top plate), so that only the corresponding parts (such as nuts and single frame plates) need to be replaced when local damage occurs, without the need for overall replacement, and the replacement cost is reduced by more than 60%; at the same time, the high-temperature isolation performance of tungsten is retained, and carbon pollution after sample annealing is avoided.

[0025] The present application uses a thickened bottom plate to improve the structural strength and prolong the service life to more than 30 sintering cycles; the frame is fixed with four thin tungsten plates (5mm thick) by tungsten screws, which is suitable for high-temperature thermal expansion, avoids weld cracking, and ensures the sealing performance; the top plate is designed with reinforcing ribs, and the sag rate is reduced to below 5%, which stably maintains the isolation ring.

[0026] The present application raises the vacuum degree of the high-temperature section of 1600 DEG C to 2000 DEG C to 1*10 -3 Pa, facilitating full discharge of pores; the stepwise temperature rising (1200 DEG C for 120 min; 1600 DEG C for 140 min; 2000 DEG C for 800 min) ensures uniform sintering inside and outside the sample, and finally realizes ceramic density of greater than or equal to 99% and visible light transmittance of greater than or equal to 78% (such as lanthanum zirconate gadolinium ceramic).

[0027] The present application improves the qualified rate to more than 90% by split machining (the bottom plate, the frame, and the top plate are machined separately); meanwhile, different sizes of the frame or the top plate can be replaced to flexibly adapt to various large-size sample specifications, and the universality is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is an assembly schematic diagram of the split tungsten isolation tool of the present application in addition to the tungsten cover plate; Figure 2 is a tungsten cover plate structure schematic diagram of the present application; Figure 3 is a tungsten bottom plate structure schematic diagram of the present application; Figure 4 is a tungsten long side plate structure schematic diagram of the present application; Figure 5 is a tungsten short side plate structure schematic diagram of the present application; Figure 6 is a tungsten connecting plate structure schematic diagram of the present application; Figure 7 is a tungsten short reinforcing rib structure schematic diagram of the present application; Figure 8 is a tungsten long reinforcing rib structure schematic diagram of the present application; In the figure: 1, tungsten bottom plate, 2, tungsten long side plate, 3, tungsten short side plate, 4, tungsten cover plate, 5, tungsten boat frame around, 6, tungsten connecting plate, 7, material cavity, 8, tungsten long reinforcing rib, 9, tungsten short reinforcing rib, 10, first connecting part, 11, second connecting part, 12, connecting plate through hole, 13, side plate through hole, 14, first tungsten connecting piece, 15, cover plate through hole, 16, reinforcing rib through hole, 17, boss. DETAILED DESCRIPTION

[0029] The present application will be further described below with reference to the accompanying drawings.

[0030] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", and "connection" should be understood in a broad sense, for example, it can be fixed connection, or indirect connection through an intermediate medium, or internal communication of two elements or interaction relationship of two elements. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are terms of reference and indicate the orientation or position of the illustrated object based on the orientation or position shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0032] The terms "first", "second", "third", "fourth" and the like (if any) in the description of the present application and claims and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] The technical solutions of the present application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0035] Please refer to Figures 1-8 , Figure 1 is an assembly schematic diagram of the split tungsten manufacturing isolation tool cover plate of the present application, Figure 2 is a structure schematic diagram of the tungsten cover plate of the present application, Figure 3 is a structure schematic diagram of the tungsten bottom plate of the present application, Figure 4 is a structure schematic diagram of the tungsten long side plate of the present application, Figure 5 is a structure schematic diagram of the tungsten short side plate of the present application, Figure 6 is a structure schematic diagram of the tungsten connecting plate of the present application,Figure 7 is a schematic diagram of a tungsten short reinforcing rib structure of the present application, Figure 8 is a schematic diagram of a tungsten long reinforcing rib structure of the present application.

[0036] A split tungsten isolation tool comprises a tungsten bottom plate 1, two tungsten long side plates 2, two tungsten short side plates 3, and a tungsten cover plate 4. The two tungsten long side plates 2 and the two tungsten short side plates 3 form a tungsten boat surrounding frame 5. The adjacent tungsten long side plate 2 and the tungsten short side plate 3 are connected by a tungsten connecting plate 6. The tungsten boat surrounding frame 5 is a material cavity 7. The tungsten cover plate 4 is connected with a tungsten reinforcing rib group for preventing the cover plate from collapsing. The tungsten cover plate 4 covers the tungsten boat surrounding frame 5.

[0037] The two tungsten long side plates 2 and the two tungsten short side plates 3 are fixed by the tungsten connecting plate 6 to form the tungsten boat surrounding frame 5, which replaces the existing welding fixing mode, can adapt to the thermal expansion effect under high temperature, and avoids weld cracking. The tungsten reinforcing rib group is connected to the tungsten cover plate 4, which on the one hand enhances the structural rigidity of the tungsten cover plate 4, prevents the tungsten cover plate 4 from collapsing due to its own weight or thermal stress under 2000℃ high temperature, and guarantees the stability of the isolation space inside the tool, and on the other hand forms a “plate-rib” support structure, further reduces the risk of cover plate collapse, and at the same time does not affect the overall sealing of the tool, the collapse rate is reduced to below 5%, and the isolation ring is stably maintained.

[0038] In one or more specific embodiments of the present application, in order to improve the structural strength, withstand the weight of large-size ceramic samples and 2000℃ high temperature impact, and avoid deformation and cracking during long-term use, the thickness of the tungsten bottom plate 1 is 18mm, and the service life is extended to more than 30 sintering cycles.

[0039] In one or more specific embodiments of the present application, the thickness of the tungsten cover plate 4 is 5mm.

[0040] In one or more specific embodiments of the present application, the tungsten connecting plate 6 comprises a first connecting part 10 and a second connecting part 11. The included angle between the first connecting part 10 and the second connecting part 11 is a right angle. Connecting plate through holes 12 are formed in the first connecting part 10 and the second connecting part 11. Side plate through holes 13 are formed in the two tungsten long side plates 2 and the two tungsten short side plates 3. A first tungsten connecting piece 14 is connected between each connecting plate through hole 12 and the side plate through hole 13 matched therewith. The first tungsten connecting piece 14 comprises a tungsten screw and a tungsten nut, which are connected, adapt to high-temperature thermal expansion, avoid weld cracking, and guarantee sealing.

[0041] In one or more specific embodiments of the present application, the tungsten reinforcing rib group comprises one tungsten long reinforcing rib 8 and two tungsten short reinforcing ribs 9. The tungsten long reinforcing rib 8 is connected to one pair of diagonal lines of the tungsten cover plate 4. The two tungsten short reinforcing ribs 9 are connected to the other pair of diagonal lines of the tungsten cover plate 4.

[0042] In one or more embodiments of the present application, a cover plate through hole 15 is formed on the diagonal line of the tungsten cover plate 4, a reinforcing rib through hole 16 is formed on the tungsten long reinforcing rib 8 and the tungsten short reinforcing rib 9, and a second tungsten connecting piece is connected between each cover plate through hole 15 and the reinforcing rib through hole 16 matched therewith, the second tungsten connecting piece comprising a tungsten screw and a tungsten nut, the tungsten screw and the tungsten nut being connected and being adapted to high-temperature thermal expansion to avoid weld cracking and ensure sealing.

[0043] In one or more embodiments of the present application, a boss 17 is arranged on the tungsten bottom plate 1, and the bottom of the tungsten boat peripheral frame 5 is sleeved on the boss 17.

[0044] By designing a split type (composed of a tungsten bottom plate, a tungsten boat peripheral frame 5, and a tungsten cover plate 4), when a local damage occurs, only the corresponding components (such as nuts and single plates) need to be replaced, without the need for overall replacement, and the replacement cost is reduced by more than 60%; at the same time, the high-temperature insulation performance of tungsten is retained, and carbon contamination after sample annealing is ensured.

[0045] The assembly process of the split-type tungsten isolation tool of the present application is as follows: M1, connect the tungsten connecting plate 6 to the two tungsten long side plates 2 and the two tungsten short side plates 3 by using tungsten screws and tungsten nuts to form the tungsten boat peripheral frame 5; connect the tungsten long reinforcing rib 8 and the tungsten short reinforcing rib 9 to the tungsten cover plate 4 by using tungsten screws and tungsten nuts to form a cover plate with reinforcing ribs.

[0046] M2, press the tungsten boat peripheral frame 5 downward to be sleeved on the boss 17 of the tungsten bottom plate 1.

[0047] M3, during sintering, place a large-size ceramic sample (such as a lanthanum gadolinium zirconate green body) into the material cavity 7, ensure that the sample does not directly contact the wall of the tungsten boat peripheral frame 5 (leave a thermal expansion gap of 1mm~2mm), cover the cover plate with reinforcing ribs, align the tungsten cover plate 4 with the top edge of the tungsten boat peripheral frame 5, lightly fix (avoid over-tightening to cause stress cracking at high temperature) by using tungsten screws through the top hole (not shown in the figure), complete the assembly of the whole tool, and place the assembled split-type tungsten isolation tool into a graphite vacuum furnace, the tool insulates the sample from the graphite furnace body as a whole, and prevents carbon contamination.

[0048] Example 1 Synthesize lanthanum gadolinium zirconate ceramic powder by a solid phase method, form a green body by mold pressing, and the forming pressure is 20MPa. Then, further improve the density of the green body by cold isostatic pressing, and the forming pressure is 300MPa after forming. The size of the green body is 120mm in diameter and 8mm in thickness.

[0049] In the following example 2 and comparative example 1, the green body is the same batch of green body prepared in example 1.

[0050] In the following Example 3 and Comparative Example 2, the green body at each corresponding sintering time is the same batch, for example, the green body for the first sintering of Example 3 and the first sintering of Comparative Example 2 is the same batch, the green body for the second sintering of Example 3 and the second sintering of Comparative Example 2 is the same batch, and so on.

[0051] In the following Example 2-Example 3, Comparative Example 1-Comparative Example 2, the graphite vacuum furnace is the same graphite vacuum furnace.

[0052] Example 2 A sintering method of large-size transparent ceramics, comprising the following steps: S1, taking the green body of Example 1, placing it into the material cavity 7 of the split tungsten-made insulation tool, covering the cover plate with reinforcing ribs, and then placing the tool into the graphite vacuum furnace, the effective size of the split tungsten-made insulation tool is 380*550*60mm; S2, sintering: S21, low-temperature preheating stage, parameters: 1*10 -2 Pa, heating to 1200℃ within 300min.

[0053] The purpose of this stage is to remove the residual moisture and low-boiling-point impurities in the ceramic body, to avoid cracking of the body due to the rapid evaporation of moisture at low temperature.

[0054] S22, medium-temperature transition stage, parameters: 1*10 -2 Pa, holding at 1200℃ for 120min.

[0055] The purpose of this stage is to prepare for high-temperature densification at the sintering critical point, to avoid excessive temperature difference leading to internal stress.

[0056] S23, high-temperature heating stage: S231, first section of high-temperature heating stage, parameters: 1*10 -2 Pa, heating to 1600℃ within 200min.

[0057] S232, second section of high-temperature heating stage, parameters: 6*10 -3 Pa, holding at 1600℃ for 120min.

[0058] The purpose of S231 and S232 is to establish a high-vacuum environment in advance, to lay a foundation for the discharge of pores in the high-temperature section.

[0059] S233, third section of high-temperature heating stage, parameters: 3*10 -3 Pa, heating to 1850℃ within 1000min.

[0060] The slow heating in this stage is because large-sized samples have slow thermal conduction, and the excessively rapid heating would cause the internal and external temperature difference to exceed 50°C. This stage initiates the ceramic densification process.

[0061] S24, High-temperature insulation stage, parameters are: 1*10 -3 Pa, heat at 1850℃ for 1080 min.

[0062] This stage ensures uniform sintering inside and outside the large-size sample, fully removes internal pores, and improves density.

[0063] S25, during the slow cooling phase, the parameters are: 1*10 -3 Pa, first cool to 1200℃ within 325 minutes, then cool to 500℃ within 175 minutes, and then allow to cool naturally.

[0064] This stage avoids rapid cooling that could cause the ceramic to crack due to thermal expansion and contraction, thus ensuring the integrity of the product.

[0065] The performance of the sintered lanthanum gadolinium zirconate ceramic was tested, and the results are shown in Table 1 below.

[0066] Comparative Example 1 A sintering method for large-size transparent ceramics includes the following steps: S1. Take the green blank from Example 1 and place it into the material cavity 7 of the split tungsten isolation tooling of the present invention. After covering it with a cover plate with reinforcing ribs, place the tooling into a graphite vacuum furnace. S21, Low-temperature preheating stage, parameters: 5*10 -2 Pa, heated to 1200℃ within 300 min.

[0067] S22, intermediate temperature transition stage, parameters: 5*10 -2 Pa, hold at 1200℃ for 120 min.

[0068] S23, High-temperature heating stage: S231, the first stage of the high-temperature heating phase, with parameters of 1*10. -2 Pa, heated to 1600℃ within 200 minutes.

[0069] S232, the second stage of the high-temperature heating phase, with parameters of 6*10. -3 Pa, hold at 1600℃ for 120 min.

[0070] S233, the third stage of the high-temperature heating phase, with parameters of 6*10. -3 Pa, heated to 1850℃ within 1000 min.

[0071] S24, High-temperature insulation stage, parameters are: 6*10-3 Pa, 1850℃ for 1080 min.

[0072] S25, slow cooling stage, parameters: 6*10 -3 Pa, first cooling to 1200℃ in 325 min, then cooling to 500℃ in 175 min, and then natural cooling.

[0073] The sintered lanthanum zirconate gadolinium ceramic was subjected to performance detection, and the results are shown in Table 1.

[0074] Table 1 Example 3 The green body of Example 1 was taken, the sintering process of Example 2 was adopted, the tooling was the split tungsten tooling of the application (i.e. the tooling adopted in Example 2), and the lanthanum zirconate gadolinium ceramic was sintered for 8 times.

[0075] Comparative Example 2 The green body of Example 1 was taken, the sintering process of Example 2 was adopted, the tooling was the existing integral tungsten tooling, the integral tungsten tooling had the same effective size as that of Example 2, and the lanthanum zirconate gadolinium ceramic was sintered for 8 times.

[0076] The lanthanum zirconate gadolinium ceramic sintered for the last time in Example 3 and Comparative Example 2 was taken, and the carbon content was detected, and the results are shown in Table 2.

[0077] Table 2 The above only describes the preferred embodiments of the application and is not used to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A split-type tungsten insulating tool, characterized in that, It includes a tungsten base plate, two long tungsten side plates, two short tungsten side plates, and a tungsten cover plate. The two long tungsten side plates and the two short tungsten side plates form the frame around the tungsten boat. Adjacent long tungsten side plates and short tungsten side plates are connected by tungsten connecting plates. The frame around the tungsten boat is a material cavity. The side of the tungsten cover plate facing the material cavity is connected to a tungsten reinforcing rib group for preventing the cover plate from collapsing. The tungsten cover plate covers the frame around the tungsten boat.

2. The split-type tungsten insulating tooling according to claim 1, characterized in that, The tungsten base plate is 18mm thick, and the tungsten cover plate is 5mm thick.

3. The split-type tungsten insulating tooling according to claim 1, characterized in that, The tungsten connecting plate includes a first connecting part and a second connecting part, with a right angle between the first connecting part and the second connecting part. Both the first connecting part and the second connecting part are provided with connecting plate through holes. Both the two long tungsten side plates and the two short tungsten side plates are provided with side plate through holes. A first tungsten connector is connected between each connecting plate through hole and its mating side plate through hole. The first tungsten connector includes a tungsten screw and a tungsten nut.

4. The split-type tungsten insulating tooling according to claim 1, characterized in that, The tungsten reinforcing rib assembly includes one long tungsten reinforcing rib and two short tungsten reinforcing ribs. The long tungsten reinforcing rib is connected to one diagonal of the tungsten cover plate, and the two short tungsten reinforcing ribs are connected to the other diagonal of the tungsten cover plate.

5. The split-type tungsten insulating tooling according to claim 1, characterized in that, The tungsten cover plate has a cover plate through hole on its diagonal, and the tungsten long reinforcing rib and the tungsten short reinforcing rib each have a reinforcing rib through hole. A second tungsten connector is connected between each cover plate through hole and its matching reinforcing rib through hole. The second tungsten connector includes a tungsten screw and a tungsten nut.

6. The split-type tungsten insulating tooling according to claim 1, characterized in that, The tungsten base plate is provided with a boss, and the bottom of the frame around the tungsten boat is fitted onto the boss.

7. A sintering method for large-size transparent ceramics, characterized in that, Includes the following steps: S1, take the green blank, put it into the material cavity of the split tungsten insulating tool as described in any one of claims 1-6, and then place the split tungsten insulating tool into a graphite vacuum furnace. S2, sintering: S21, Low-temperature preheating stage, parameters: 1*10 -2 Pa, heat to the sintering critical point within 300 min; S22, intermediate temperature transition stage, parameters: 1*10 -2 Pa, hold at the critical sintering point for 120 min; S23, High-temperature heating stage: S231, the first stage of the high-temperature heating phase, with parameters of 1*10. -2 Pa, heated to 1600℃ within 200 minutes; S232, the second stage of the high-temperature heating phase, with parameters of 6*10. -3 Pa, heat at 1600℃ for 120 min; S233, the third stage of the high-temperature heating phase, with parameters of 6*10. -3 Pa, heated to 1850℃ within 1000 min; S24, High-temperature insulation stage, parameters are: 6*10 -3 Pa, heat at 1850℃ for 1080 min; S25, during the slow cooling phase, the parameters are: 6*10 -3 Pa, first cool to 1200℃ within 325 minutes, then cool to 500℃ within 175 minutes, and then allow to cool naturally.

8. The sintering method for large-size transparent ceramics according to claim 7, characterized in that, The effective dimensions of the split-type tungsten insulating tool are 380*550*60mm.

9. The sintering method for large-size transparent ceramics according to claim 7, characterized in that, In S1, the assembly and green billet feeding of the split-type tungsten insulating tooling includes the following steps: M1, use tungsten screws and nuts to connect the tungsten connecting plate to the two long tungsten side plates and the two short tungsten side plates to form the frame around the tungsten boat; use tungsten long reinforcing ribs and tungsten short reinforcing ribs to connect to the tungsten cover plate with tungsten screws and nuts to form a cover plate with reinforcing ribs; M2, press the frame of the tungsten boat downwards onto the protrusion of the tungsten base plate; M3, the green billet is placed into the material cavity and covered with a cover plate with reinforcing ribs.

10. The sintering method for large-size transparent ceramics according to claim 7, characterized in that, The large-size transparent ceramic is a lanthanum gadolinium zirconate ceramic with a diameter of 100 mm and a thickness of 5 mm.

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