Novel reaction sintering boron carbide ceramic self-infiltration connection method

Abstract

The invention relates to the technical field of ceramic welding, in particular to a novel reaction sintering boron carbide ceramic self-infiltration connection method. According to the method, the to-be-connected surfaces of the reactive sintering boron carbide ceramics are polished to be consistent in roughness at the normal temperature and then pressed, the two reactive sintering boron carbide ceramics can be successfully connected at the high temperature through diffusion and interface reaction of residual silicon of the reactive sintering boron carbide ceramics, and the formed connecting layer mainly comprises three phases of Si, SiC and B12 (C, Si, B) 3; compared with the prior art, the method has the advantages that the adaptability between the connecting layer and the base material boron carbide is good, almost most of the mechanical properties of the base material boron carbide are reserved, in addition, many fine silicon carbide phases are formed at the interface, and the interface bonding is good, so that the connection of the reactive sintering boron carbide ceramic is simply realized under the condition of not adding any middle layer, and the service life of the reactive sintering boron carbide ceramic is prolonged. And a connection interface is complete, defects such as air holes are few, and most of the bending strength is reserved.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic welding, in particular to a novel self-penetration connection method of reaction-sintered boron carbide ceramics. Background Art

[0002] Boron carbide has many excellent properties due to its special crystal structure with strong covalent bonds as the main body, such as high melting point, high hardness, low density, good thermal stability, wear resistance, strong chemical corrosion resistance and strong neutron absorption ability. It is currently widely used in military engineering, mechanical industry, chemical engineering, aerospace and nuclear industry. In the actual application conditions in these fields, there are often greater requirements for the size or shape of boron carbide ceramics. Therefore, research on the preparation of large-sized and complex-shaped boron carbide ceramics has become more and more popular.

[0003] In the current research, the sintering process of boron carbide ceramics is divided into pressureless sintering, hot pressing sintering, SPS sintering and reaction sintering. For pressureless sintering and reaction sintering, it is usually necessary to press the green body before sintering, while hot pressing sintering and SPS sintering directly put the powder into the mold cavity and perform the molding and sintering process at the same time. However, no matter which molding or sintering method is used, the size of the prepared boron carbide ceramics will almost be limited by the mold size or the furnace cavity size. Reaction sintering has the advantages of low sintering temperature, short preparation cycle, net size sintering, and low sintering cost. Therefore, reaction sintering to prepare boron carbide is a simple process and is more suitable for industrial production. Sintering method, however, the preparation of reaction sintered boron carbide ceramics may be subject to problems such as large size is difficult to penetrate completely or uneven penetration, so it is difficult to directly prepare large-size reaction sintered boron carbide ceramics.

[0004] Based on the above research background, some researchers have proposed the idea of ​​using small-sized boron carbide to connect and indirectly prepare large-sized boron carbide ceramics. Ceramic connection technology is expected to become an effective way to solve the problem of preparing large-sized boron carbide ceramics. Therefore, how to effectively achieve the connection of small-sized boron carbide ceramics and ensure the stability of the joints has become a research focus in this field.

[0005] Existing ceramic connection methods include mechanical connection, diffusion connection, transient liquid phase connection, ceramic brazing, reaction connection, etc. Mechanical connection is achieved by a mechanical structure similar to rivets, and the joints are relatively weak; while diffusion connection and transient liquid phase connection require very harsh connection conditions, such as high temperature and the need to apply a large load pressure during connection, which limits their production and application; ceramic brazing and reaction connection are to fill metal brazing material or ceramic intermediate layer between ceramics, and achieve interface bonding through reaction process or small amount of diffusion, but it is difficult to achieve, and it is necessary to overcome the problem of instability of the interface and connection layer between ceramics and heterogeneous materials. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a novel reaction sintered boron carbide ceramic self-penetration connection method, which solves the technical problem of stability at the boron carbide ceramic connection joint.

[0008] (II) Technical solution

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] The embodiment of the present invention provides a novel self-penetration connection method of reaction-sintered boron carbide ceramics.

[0011] A novel reaction-sintered boron carbide ceramic self-penetration connection method proposed in an embodiment of the present invention is characterized by comprising the following steps:

[0012] S1: After dissolving phenolic resin in anhydrous ethanol, the mixture is added into a ball mill containing boron carbide powder for ball milling to obtain a base material slurry;

[0013] The parent material slurry is dried, ground, sieved, dry pressed and vacuum siliconized and sintered to obtain a reaction sintered boron carbide ceramic parent material;

[0014] S2: After the reaction-sintered boron carbide ceramic base material is ground flat, the surface of the reaction-sintered boron carbide ceramic base material to be connected is polished to obtain a reaction-sintered boron carbide ceramic base material with the same surface roughness as the surface to be connected;

[0015] The reaction-sintered boron carbide ceramic matrix materials with the same surface roughness to be connected are placed in anhydrous ethanol for ultrasonic cleaning, and dried to obtain the reaction-sintered boron carbide ceramic matrix materials to be connected;

[0016] S3: Butt the surfaces of two reaction-sintered boron carbide ceramic base materials to be connected, put them into a graphite fixture coated with boron nitride, clamp them, put them into a graphite vacuum furnace together with the graphite fixture, heat them to the connection temperature under vacuum conditions, keep them warm for a period of time, and then cool them to room temperature with the furnace to obtain a reaction-sintered boron carbide ceramic base material connection material.

[0017] According to the present invention, in step S1, the average particle size of the boron carbide powder is 1.9 μm, and the particle size range is 1.4-2.5 μm.

[0018] According to the present invention, in step S1, the ball milling method is horizontal ball milling, and the ball milling time is 24 hours.

[0019] According to the present invention, in step S1, the drying time is at least 20 hours to 24 hours, the sieve mesh is 60 mesh, the dry pressing unidirectional pressing load is 200 MPa, and the holding time is 10 seconds.

[0020] According to the present invention, in step S1, the heating rate of vacuum siliconizing sintering from 1100°C to 1550-1600°C is 5°C / min-10°C / min, the holding temperature is 1540-1600°C, the holding time is 30min-45min, the vacuum degree is 40Pa-60Pa, and the cooling method is furnace cooling.

[0021] According to the present invention, in step S1, the boron carbide powder is added in an amount of 90-95 wt. % by mass, and the phenolic resin is added in an amount of 10-5 wt. % of residual C after carbonization.

[0022] According to the present invention, in step S1, the phenolic resin is an alcohol-soluble phenolic resin with a solid content of 53% and free phenol ≤ 15%.

[0023] According to the present invention, in step S2, the surface to be connected of the reaction-bonded boron carbide ceramic base material is polished by a polishing paste of 0.5-2.5 μm.

[0024] According to the present invention, in step S2, the base material to be connected is cleaned by being placed in deionized water or anhydrous ethanol for 10 to 20 minutes and dried for 12 to 20 hours.

[0025] According to the present invention, in step S2, when grinding the surfaces of the reaction-sintered boron carbide ceramic base material to be connected, the two surfaces to be connected are arranged in parallel to increase the contact area of ​​the surfaces to be connected when the subsequent clamps apply pressure.

[0026] According to the present invention, in step S3, during the connection process, the heating rate of the graphite vacuum furnace from 1100°C to 1450-1600°C is 5°C / min-10°C / min, the insulation temperature is 1450-1600°C, the insulation time is 15min-20min, the vacuum degree is 35Pa-55Pa, the cooling method is furnace cooling, and the clamp is kept clamped during the whole process.

[0027] According to the present invention, in step S3, when the surfaces to be connected are butted, the two surfaces to be connected are closely fitted together.

[0028] (III) Beneficial effects

[0029] The beneficial effects of the present invention are as follows: the present invention is a novel self-infiltration connection method for reaction-sintered boron carbide ceramics. The present invention presses the reaction-sintered boron carbide ceramics at room temperature, and can successfully connect two pieces of reaction-sintered boron carbide ceramics at high temperature through the diffusion of residual silicon and interface reaction. The components of the formed connection area are mainly Si, SiC, B 12 The three phases (C, Si, B)3 have good compatibility with the parent material boron carbide, and almost most of the mechanical properties of the parent material boron carbide are retained. In addition, many fine silicon carbide phases are formed at the interface, and the interface bonding is good. Therefore, the present invention realizes the connection of reaction-sintered boron carbide ceramics in a relatively simple manner without adding any intermediate layer, and the connection interface is complete, there are no defects such as pores, and most of the bending strength is retained. This new self-infiltration connection method of reaction-sintered boron carbide ceramics has been successfully developed, providing a new method for preparing large-size reaction-sintered boron carbide ceramics, and can achieve high repetition rate and low cost, which is more suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the process of a novel reaction sintered boron carbide ceramic self-infiltration connection method;

[0031] Figure 2 XRD phase composition diagram of the reaction-sintered boron carbide ceramic base material prepared in the early stage of the novel reaction-sintered boron carbide ceramic self-infiltration connection method and the reaction-sintered boron carbide ceramic connection piece prepared in the embodiment;

[0032] Figure 3 The secondary and backscattered electron images of the SEM of the RBBC base material of the new reaction sintered boron carbide ceramic self-infiltration bonding method;

[0033] Figure 4 The SEM secondary and backscattered electron images of the connection layer of the RBBC connection material of the new reaction sintered boron carbide ceramic self-penetration connection method;

[0034] Figure 5 High-magnification SEM secondary and backscattered electron images of the connection layer of the RBBC connection material using a new type of reaction-sintered boron carbide ceramic self-penetration connection method;

[0035] Figure 6 This is a schematic diagram of the technical process principle of a new reaction sintered boron carbide ceramic self-penetration connection method. DETAILED DESCRIPTION

[0036] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0037] The raw material information used in the embodiments of the present invention is shown in Table 1 below.

[0038]

[0039] Table 1 Raw material information

[0040] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0041] RBBC (Reaction bonded boron carbide ceramics) are reaction bonded boron carbide ceramics prepared by silicon infiltration method.

[0042] See also Figures 1 to 6 As shown, according to the embodiment of the present application, a novel reaction sintered boron carbide ceramic self-penetration connection method is proposed, comprising the following steps:

[0043] RBBC parent material preparation:

[0044] S1: After dissolving phenolic resin in anhydrous ethanol, the mixture is added into a ball mill containing boron carbide powder for ball milling to obtain a base material slurry;

[0045] Among them, the average particle size of the boron carbide powder is 1.9μm, and the particle size range is 1.4-2.5μm; the ball milling method is horizontal ball milling, and the ball milling time is 24h; in terms of mass percentage, the amount of boron carbide powder is 90-95wt.%, and the phenolic resin is added with a residual C of 0-5wt.% after carbonization; its carbonization rate is 51%, and in the embodiments, the carbon mass fraction after carbonization is 10-5wt.% and is added into the system.

[0046] The parent material slurry is dried, ground, sieved, dry pressed and vacuum siliconized and sintered to obtain a reaction sintered boron carbide ceramic parent material;

[0047] Among them, the drying time is at least 20h~24h, the sieving mesh number is 60 mesh sieve, the unidirectional pressing load of dry pressing molding is 200MPa, and the holding time is 10s; the heating rate of vacuum silicon infiltration sintering from 1100℃ to 1550~1600℃ is 5℃ / min-10℃ / min, the holding temperature is 1540~1600℃, the holding time is 30min~45min, the vacuum degree is 40Pa~60Pa, and the cooling method is furnace cooling.

[0048] RBBC base material processing:

[0049] S2: After grinding and polishing the reaction-sintered boron carbide ceramic base material, the surface of the reaction-sintered boron carbide ceramic base material to be connected is polished to obtain a reaction-sintered boron carbide ceramic base material with the same surface roughness as the surface to be connected;

[0050] Wherein, the surface to be connected of the reaction-sintered boron carbide ceramic base material is polished by a polishing paste of 0.5 to 2.5 μm;

[0051] The reaction-sintered boron carbide ceramic matrix materials with the same surface roughness to be connected are placed in anhydrous ethanol for ultrasonic cleaning, and dried to obtain the reaction-sintered boron carbide ceramic matrix materials to be connected;

[0052] The base material to be connected is cleaned by placing it in deionized water or anhydrous ethanol for 10 to 20 minutes and dried for 12 to 20 hours.

[0053] When grinding the surfaces of the reaction-sintered boron carbide ceramic base material to be connected, the two surfaces to be connected are arranged in parallel to increase the contact area of ​​the surfaces to be connected when the subsequent clamps apply pressure;

[0054] RBBC connection process:

[0055] S3: butting the surfaces of two reaction-sintered boron carbide ceramic base materials to be connected, placing them in a graphite fixture coated with boron nitride, clamping them, and placing them together with the graphite fixture in a graphite vacuum furnace, heating them to a connection temperature under vacuum conditions, keeping them warm for a period of time, and cooling them to room temperature with the furnace to obtain a reaction-sintered boron carbide ceramic base material connection material;

[0056] Among them, during the connection process, the heating rate of the graphite vacuum furnace from 1100℃ to 1450~1600℃ is 5℃ / min-10℃ / min, the insulation temperature is 1450~1600℃, the insulation time is 15min~20min, the vacuum degree is 35Pa~55Pa, and the cooling method is furnace cooling; BN coating on the graphite fixture can protect the fixture from being consumed by silicon gas at high temperature;

[0057] When the surfaces to be connected are butt-jointed, the two surfaces to be connected fit tightly together. When the surfaces to be connected are butt-jointed, the two surfaces need to be completely clamped with a clamp, and the thickness of the gap left between the two surfaces will directly affect the overall thickness of the connection layer after connection.

[0058] In the embodiment of the present invention, the average particle size of the B4C powder used to prepare the RBBC mother material is 1.6μm, and the particle size range is 1.4-2.5μm; the phenolic resin used to prepare the RBBC mother material is a 2124 series thermosetting (novolac type) alcohol-soluble phenolic resin with a solid content of 53%. The solid content of 53% means that in this alcohol-soluble phenolic resin, the solid component (phenolic resin itself) accounts for 53% of the mass proportion of the entire resin system, and the free phenol is ≤15%; the amount of B4C used to prepare the RBBC mother material is 90wt.%, and the phenolic resin is added with a residual C content of 10wt.% after carbonization.

[0059] The equipment used for the infiltration reaction sintering in the embodiment of the present invention is a vacuum graphite reaction sintering furnace.

[0060] In the embodiment of the present invention, the Archimedes drainage method is used to measure the volume density and open porosity of the RBBC base material and the RBBC connecting material.

[0061] In the embodiment of the present invention, a Smartlab (9) type X-ray diffractometer is used to analyze the phase composition of the ceramic composite material. The reaction sintered boron carbide ceramic matrix prepared in the early stage is composed of B 12 The connection layer of the prepared reaction sintered boron carbide ceramic connection material is mainly composed of Si and a small amount of B 12 It is composed of three phases: (C, Si, B)3 and newly formed SiC.

[0062] The prepared RBBC connection material basically retains the phase composition of RBBC, and its connection layer is mainly composed of Si and a small amount of B 12 The RBBC bonding material is composed of (C, Si, B)3 and newly formed SiC three-phase, and the bonding layer is well bonded with the reaction-sintered boron carbide base material; the prepared RBBC bonding material basically retains the low density and low open porosity of RBBC, and its volume density is 2.51-2.56 (±0.01) g / cm 3 , the open porosity is 0.27-0.57 (±0.1)%; the prepared RBBC connecting material basically retains the flexural strength of RBBC, and its flexural strength is 170-200 (±20) Mpa, and the flexural strength retention rate is 81.0-96.7%; the prepared RBBC connecting material basically retains the Vickers hardness of the RBBC parent material; compared with other connection methods, the prepared RBBC connecting material of the present invention maintains the advantages of low density, corrosion resistance and high hardness of the parent material, and can replace reaction sintered boron carbide ceramics for application in various scenarios.

[0063] In the embodiment of the present invention, a scanning electron microscope (JSM-7001F) was used to observe the microstructure of the reaction-sintered boron carbide ceramic base material and the connecting material.

[0064] In the embodiments of the present invention, the three-point bending method is used to measure the bending strength of the RBBC base material and the RBBC connection material, and the instrument used is an AG-Xplus100kN electronic universal testing machine manufactured by Japan Co., Ltd.

[0065] Embodiment 1:

[0066] The preparation method of reaction sintered boron carbide ceramic connection material consists of the following steps:

[0067] First, it is necessary to prepare the RBBC mother material. First, according to 90wt.% B4C and 10wt.% C (the actual phenolic resin content is calculated according to the C content based on the carbonization rate of the phenolic resin), the phenolic resin is first dissolved in anhydrous ethanol and completely dissolved, and then added to a ball mill containing boron carbide powder and large and small balls for ball milling. After ball milling, the slurry is put into an oven, and after the slurry is dried, it is taken out and ground, sieved, dry pressed, and vacuum siliconized and sintered to obtain the RBBC mother material. The volume density of the RBBC mother material prepared in this embodiment is 2.56 (± 0.02) g / cm 3 The open porosity is 0.36 (± 0.1)%, the flexural strength is 205.8 (± 50.9) MPa, the hardness is 15.82 (± 3.75) GPa, and its X-ray diffraction pattern is as follows Figure 2 , SEM secondary electron images such as Figure 3 (a), (b), backscattered electron images such as Figure 3 (c)(d), where (a)(c) is 300 times, and (b)(d) is 1000 times.

[0068] After the RBBC mother material is ground and polished by a diamond grinding disc and a grinder, the surface to be connected is polished to ensure that the surfaces to be connected are polished to the same roughness with a 0.5 μm diamond polishing paste, and then ultrasonically cleaned in anhydrous ethanol for 15 minutes and dried to obtain the RBBC mother material to be connected;

[0069] The two polished surfaces of the RBBC base material to be connected are butt-jointed, clamped in a graphite fixture coated with BN, and then placed in a graphite vacuum furnace together with the fixture. Under vacuum conditions, the temperature is quickly raised to 1100°C for 1 hour, and then heated from 1100°C to 1450°C at a heating rate of 5°C per minute. After keeping warm for 20 minutes, it is cooled to room temperature with the furnace to finally obtain the RBBC connection material; the cooled RBBC connection material is taken out, cut and polished to the standard bending strength sample size, and used to test the bending strength of the RBBC connection material.

[0070] In this embodiment, the volume density of the prepared RBBC connecting material is 2.55 (± 0.01) g / cm 3; The open porosity is 0.27 (± 0.07) %; the flexural strength is 170.2 (± 15.9) MPa, and the flexural strength retention rate (flexural strength of the connecting material / flexural strength of the parent material) is 82.7%; the overall Vickers hardness of the connecting part is 15.29 (± 1.37) GPa. The SEM secondary electron image of the connecting layer of the connecting material is as follows Figure 4 (a) Figure 5 (a), backscattered electron image Figure 4 (e) Figure 5 (e) where: Figure 4 300 times, Figure 5 It is 1000 times.

[0071] from Figure 4 It can be seen from (a) and (e) that the connection interface is relatively smooth as a whole, without obvious pores and defects, and with a small amount of B 12 (C, Si, B)3 migrates from the RBBC base material to the middle of the connecting layer. According to the dissolution precipitation mechanism, the temperature is lower at this time, and there is a greater B and C concentration gradient from the interface to the middle of the connecting layer. 12 (C, Si, B)3 grains tend to grow toward the front end, so they are mainly in the shape of fine needles; Figure 5 It can be seen from (a) and (e) that many needle-shaped SiC are also generated at the interface. At this time, the reinforcement effect on the interface and the connecting layer is not obvious, so the bending strength retention rate is only 82.7%.

[0072] Example 1 is an example of reaction-sintered boron carbide ceramic self-penetration bonding, in which the self-penetration bonding process is completed at 1450° C., and a reaction-sintered boron carbide ceramic bonding material is obtained.

[0073] Embodiment 2:

[0074] The preparation of the RBBC mother material is the same as that in Example 1. The RBBC mother material prepared in the same batch as in Example 1 is used for the subsequent self-infiltration connection process. The steps of polishing, cleaning, placing the RBBC mother material in a fixture, and placing it in a graphite vacuum furnace are the same as in Example 1, except that it is heated to 1500°C at a heating rate of 5°C per minute at 1100°C under vacuum conditions, kept warm for 20 minutes, and then cooled to room temperature with the furnace to finally obtain the RBBC connection material.

[0075] The cooled RBBC connection material is taken out, cut and polished to the standard bending strength sample size for testing the bending strength of the RBBC connection material.

[0076] In this embodiment, the RBBC connection material prepared has a thickness of 2.56 (± 0.01) g / cm 3; The open porosity is 0.34 (± 0.15) %; the flexural strength is 199 (± 17.7) MPa, and the flexural strength retention rate (flexural strength of the connecting material / flexural strength of the parent material) is 96.7%; the overall Vickers hardness of the connecting part is 15.53 (± 0.67) GPa. The SEM secondary electron image of the connecting layer of the connecting material is as follows Figure 4 (b) Figure 5 (b), backscattered electron image Figure 4 (f) Figure 5 (f), where Figure 4 is 300 times, Figure 5 It is 1000 times.

[0077] from Figure 4 As can be seen from (b) and (f), the connection interface is relatively smooth as in Example 1, with no obvious pores or defects, and a small amount of B 12 (C, Si, B)3 migrates from the RBBC base material to the middle of the connecting layer, at this time the temperature rises a little, B 12 In addition to growing toward the front end, (C, Si, B)3 has enough energy to promote its uniform growth toward the side. Therefore, compared with Example 1, it is mainly in the form of small blocks and distributed in the middle area of ​​the connecting layer as a reinforcement phase. In addition, Figure 5 It can be seen from (b) and (f) that SiC also obtains enough energy at this time, and is mainly distributed in small cross-linked blocks at the interface, which promotes the interface bonding well. Therefore, the flexural strength retention rate is 96.7%, which is almost equivalent to that of the RBBC base material.

[0078] Example 2 is an example of reaction-sintered boron carbide ceramic self-penetration bonding, in which the self-penetration bonding process is completed at 1500° C. to obtain a reaction-sintered boron carbide ceramic bonding material.

[0079] Embodiment 3:

[0080] The preparation of the RBBC mother material is the same as that in Example 1. The RBBC mother material prepared in the same batch as in Example 1 is used for the subsequent self-infiltration connection process. The steps of polishing, cleaning, placing the RBBC mother material in a fixture, and placing it in a graphite vacuum furnace are the same as in Example 1, except that it is heated to 1550°C at a heating rate of 5°C per minute at 1100°C under vacuum conditions, kept warm for 20 minutes, and then cooled to room temperature with the furnace to finally obtain the RBBC connection material.

[0081] The cooled RBBC connection material is taken out, cut and polished to the standard bending strength sample size for testing the bending strength of the RBBC connection material.

[0082] In this embodiment, the RBBC connection material prepared has a thickness of 2.54 (± 0.01) g / cm 3; The open porosity is 0.45 (± 0.12) %; the bending strength is 177 (± 18.2) MPa, and the bending strength retention rate (bending strength of the connecting material / bending strength of the parent material) is 86.0%; the overall Vickers hardness of the connecting part is 15.63 (± 3.57) GPa, and the hardness retention rate is 98.7%. The SEM secondary electron image of the connecting layer of the connecting material is as follows Figure 4 (c) Figure 5 (c), backscattered electron image Figure 4 (g) Figure 5 (g) where: Figure 4 is 300 times, Figure 5 It is 1000 times.

[0083] from Figure 4 It can be seen from (c) and (g) that, like Example 1, the connection interface is relatively flat as a whole, without obvious pores and defects. Figure 5 It can be seen from (c) and (g) that at this time, the interface is mainly composed of B 12 (C, Si, B)3 composition, SiC is no longer limited to appearing only at the interface, and 12 (C, Si, B)3 also obtains enough energy to grow in all directions and eventually distributes in the silicon area of ​​the connecting layer in large blocks. Since the grains of the two phases are relatively coarse at this time, it is not conducive to hindering the expansion of cracks. Moreover, as the temperature rises, the silicon in the base material and the connecting layer will partially evaporate, resulting in a slight increase in the porosity. Therefore, the overall bending strength retention rate of the connector drops to 86.0%.

[0084] Example 3 is an example of reaction-sintered boron carbide ceramic self-penetration bonding, in which the self-penetration bonding process is completed at 1550° C., and a reaction-sintered boron carbide ceramic bonding material is obtained.

[0085] Embodiment 4:

[0086] The preparation of the RBBC mother material is the same as that in Example 1. The subsequent self-infiltration connection process is carried out using the same batch of RBBC mother materials prepared in Example 1. The steps of polishing, cleaning, placing the RBBC mother material in a fixture, and placing it in a graphite vacuum furnace are the same as in Example 1, except that it is heated to 1600°C at a heating rate of 5°C per minute at 1100°C under vacuum conditions, kept warm for 20 minutes, and then cooled to room temperature with the furnace to finally obtain the RBBC connection material.

[0087] The cooled RBBC connection material is taken out, cut and polished to the standard bending strength sample size for testing the bending strength of the RBBC connection material.

[0088] In this embodiment, the RBBC connection material prepared has a thickness of 2.51 (± 0.01) g / cm 3The open porosity is 0.57 (± 0.12)%, the bending strength is 166.8 (± 34.9) MPa, and the bending strength retention rate (bending strength of the connecting material / bending strength of the parent material) is 81.0%; the overall Vickers hardness of the connecting part is 15.41 (± 2.54) GPa. The SEM secondary electron image of the connecting layer of the connecting material is as follows Figure 4 (d) Figure 5 (d), backscattered electron image Figure 4 (h) Figure 5 (h), where Figure 4 is 300 times, Figure 5 It is 1000 times.

[0089] from Figure 4 It can be seen from (d) and (h) that, like in Example 1, the connection interface is relatively flat as a whole, without obvious pores and defects. Figure 5 It can be seen from (d) and (h) that the interface is the same as in Example 3. 12 (C, Si, B)3 is the main component, and at this time, B in the connecting layer 12 The (C,Si,B)3 and SiC grains grew coarser and the porosity increased to 0.57(±0.12)%, so the flexural strength retention rate decreased to 81.0%.

[0090] The connection interface of the reaction-sintered boron carbide connection material prepared by the present invention is flat, the connection layer is dense as a whole, and no obvious pores are seen, indicating that the two reaction-sintered boron carbide parent materials have been successfully connected into a whole through autoinfiltration.

[0091] The reaction sintered boron carbide connecting material prepared by the present invention has the same physical phase as the reaction sintered boron carbide parent material, and the connecting layer is mainly composed of Si and a small amount of B. 12 The three-phase composition of (C, Si, B)3 and newly formed SiC is good, and the connection layer is well bonded with the reaction-bonded boron carbide base material.

[0092] The reaction-sintered boron carbide connecting material prepared by the present invention substantially retains the bending strength of the parent material. Compared with other connection methods, the present invention maintains the advantages of low density, corrosion resistance and high hardness of the parent material, and can replace reaction-sintered boron carbide ceramics for application in various scenarios.

[0093] The reaction sintered boron carbide connection method provided by the present invention does not need to add other materials between two parent materials, and the reaction and connection process can be completed only by its own diffusion behavior.

[0094] The reaction-sintered boron carbide connection method provided by the present invention is not limited to the connection process of reaction-sintered boron carbide ceramics prepared by siliconization, but is also applicable to the connection process of other ceramic products, as long as a certain element in the ceramic matrix can spontaneously diffuse to the interface at a specific temperature to complete the reaction connection process.

[0095] The process flow of the invention is simple and easy to operate, and is suitable for mass production of large-size reaction-sintered boron carbide ceramics.

[0096] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0097] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A novel reaction sintered boron carbide ceramic self-penetration connection method, characterized in that: The method comprises the following steps: S1: After dissolving phenolic resin in anhydrous ethanol, the mixture is added into a ball mill containing boron carbide powder for ball milling to obtain a base material slurry; The parent material slurry is dried, ground, sieved, dry pressed and vacuum siliconized and sintered to obtain a reaction sintered boron carbide ceramic parent material; S2: After the reaction-sintered boron carbide ceramic base material is ground flat, the surface of the reaction-sintered boron carbide ceramic base material to be connected is polished to obtain a reaction-sintered boron carbide ceramic base material with the same surface roughness as the surface to be connected; The reaction-sintered boron carbide ceramic matrix materials with the same surface roughness to be connected are placed in anhydrous ethanol for ultrasonic cleaning, and dried to obtain the reaction-sintered boron carbide ceramic matrix materials to be connected; S3: Butt the surfaces of two reaction-sintered boron carbide ceramic base materials to be connected, put them into a graphite fixture coated with boron nitride, clamp them, put them into a graphite vacuum furnace together with the graphite fixture, heat them to the connection temperature under vacuum conditions, keep them warm for a period of time, and then cool them to room temperature with the furnace to obtain a reaction-sintered boron carbide ceramic base material connection material.

2. The novel reaction sintered boron carbide ceramic self-penetration connection method as claimed in claim 1, characterized in that: In step S1, the average particle size of the boron carbide powder is 1.9 μm, and the particle size range is 1.4 to 2.5 μm.

3. The novel reaction sintered boron carbide ceramic self-penetration connection method as claimed in claim 1, characterized in that: In step S1, the boron carbide powder is added in an amount of 90-95 wt.% by mass, and the phenolic resin is added in an amount of 0-5 wt.% of residual C after carbonization; The phenolic resin is an alcohol-soluble phenolic resin with a solid content of 53% and free phenol ≤ 15%.

4. The novel reaction sintered boron carbide ceramic self-penetration connection method as claimed in claim 1, characterized in that: In step S2, the surface to be connected of the reaction-bonded boron carbide ceramic base material is polished by using a polishing paste of 0.5-2.5 μm.

5. The novel reaction sintered boron carbide ceramic self-penetration bonding method as claimed in claim 1, characterized in that: In step S2, the base material to be connected is cleaned by placing it in deionized water or anhydrous ethanol for 10 to 20 minutes and drying it for 12 to 20 hours.

6. The novel reaction sintered boron carbide ceramic self-penetration connection method as claimed in claim 1, characterized in that: In step S2, when grinding the surfaces to be connected of the reaction-sintered boron carbide ceramic base material, the two surfaces to be connected are arranged in parallel to increase the contact area of ​​the surfaces to be connected when the clamp applies pressure later.

7. The novel reaction sintered boron carbide ceramic self-penetration bonding method as claimed in claim 1, characterized in that: In step S3, during the connection process, the heating rate of the graphite vacuum furnace from 1100°C to 1450-1600°C is 5°C / min-10°C / min, the insulation temperature is 1450-1600°C, the insulation time is 15min-20min, the vacuum degree is 35Pa-55Pa, and the cooling method is furnace cooling.

8. The novel reaction sintered boron carbide ceramic self-penetration bonding method as claimed in claim 1, characterized in that: In step S3, when the surfaces to be connected are butted against each other, the two surfaces to be connected fit tightly together.

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