A silicon nitride sandwich radome and a preparation method thereof

Abstract

The application belongs to the technical field of antenna cover preparation, in particular to a silicon nitride sandwich antenna cover and a preparation method thereof, the preparation method comprising the following steps: S1: mixing silicon nitride powder, sintering aids and a solvent, and drying to obtain ceramic powder; S2: mixing the ceramic powder with polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone and a dispersing agent to obtain a mixture; S3: cooling and granulating the mixture to obtain a premix; S4: printing the premix by using a fused deposition printing technology to obtain a silicon nitride antenna cover blank; S5: performing heating treatment on the silicon nitride antenna cover blank to obtain an antenna cover blank; and S6: performing sintering treatment on the antenna cover blank to obtain a silicon nitride sandwich antenna cover.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antenna cover preparation, and particularly relates to a silicon nitride sandwich antenna cover and a preparation method thereof. BACKGROUND

[0002] The antenna cover is an important device for protecting the radar antenna, is located at the front end of the system, is used for protecting the navigation antenna from being damaged, and enables the missile to effectively hit the target. The antenna cover is not only an important component of the aerodynamic shape of the missile, but also a protection device of the antenna, and is an important component indispensable to the missile. The silicon nitride-based ceramic has excellent mechanical properties, high thermal stability, and low dielectric constant, and has better ablation resistance than fused quartz, and can withstand thermal shock under the flight condition of 6-7Ma, and thus becomes the most promising antenna cover material at present.

[0003] However, the silicon nitride sandwich antenna cover prepared by the existing method is either a single-layer antenna cover or an antenna cover with simple shape and uniform wall thickness, or has the defect of poor bonding force between the blank layers, and is prone to cracking or delamination, and cannot meet the use requirements. Therefore, the existing technology cannot prepare the silicon nitride sandwich antenna cover with diversified structure and excellent mechanical properties, and seriously limits the development of the field of antenna covers. SUMMARY

[0004] In view of the above problems, the application designs a preparation method of a silicon nitride sandwich antenna cover, comprising the following steps:

[0005] S1: mixing silicon nitride powder, sintering aid and ethanol solvent, and drying to obtain ceramic powder;

[0006] S2: mixing the ceramic powder with polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone and a dispersing agent to obtain a mixture;

[0007] S3: cooling and granulating the mixture to obtain a premix;

[0008] S4: printing the premix by a fused deposition printing technology to obtain a silicon nitride antenna cover blank;

[0009] S5: heating the silicon nitride antenna cover blank to obtain an antenna cover blank;

[0010] S6: sintering the antenna cover blank to obtain a silicon nitride sandwich antenna cover.

[0011] Compared with the prior art, the mixture of the application comprises water-based components such as polyethylene glycol-600 and polyethylene glycol-2000 and plastic-based components such as polymethyl methacrylate, the mutual cooperation between the two components can improve the bonding strength between the ceramic powder and other components and the solid content of the mixture, the combination with the fused deposition printing technology can improve the bonding strength between the powders, and further improve the interlayer bonding force of the green body, so as to alleviate or avoid the cracking of the green body; the water-based components are dissolved and removed by water bath heating after the green body is formed, which is beneficial to improving the preparation efficiency and reducing the environmental pollution caused by solvent degreasing, the thermoplastic plastic as the skeleton material maintains the geometric shape and dimensional accuracy of the green body, so that the prepared silicon nitride radome structure is diversified, has few porosity defects, high density and light weight, and has good comprehensive performance.

[0012] Preferably, the silicon nitride powder is 85-91 parts by weight, and the sintering aid is 9-15 parts by weight.

[0013] The average particle size of the silicon nitride powder is 0.5-2 μm.

[0014] Preferably, the sintering aid comprises any one or more of lanthanum oxide, magnesium oxide and bismuth oxide.

[0015] The drying temperature of the drying treatment is 60-80℃, and the drying time is not less than 24 h.

[0016] Preferably, the ceramic powder in the mixture is 75-85 parts by weight, and the other components are 15-25 parts by weight in total.

[0017] The mixing method of the mixture is internal mixing, the internal mixing temperature is 160-180℃, and the internal mixing time is not less than 3 h.

[0018] Preferably, the dispersant comprises oleic acid OA.

[0019] In the preparation of the mixture of step 2, a plasticizer and a polymerization inhibitor are further added, the plasticizer comprises dibutyl phthalate DBP, and the polymerization inhibitor is phenothiazine.

[0020] The beneficial effects of the preferred embodiment are that the dispersant avoids the agglomeration of the powder, ensures the uniform wrapping of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, the dispersant and the ceramic powder, the plasticizer can improve the ductility of the green body, and the phenothiazine as the polymerization inhibitor can prevent the "self-crosslinking" effect of each organic component.

[0021] Preferably, the weight ratio of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, dispersant, plasticizer, polymerization inhibitor is (10-20):(30-40):(5-15):(10-20):(15-25):(1.9-3.5):(1-3):(0.1-0.5).

[0022] The beneficial effects of the preferred embodiment are that polyethylene glycol-600 is used as a lubricant and wetting agent to wet the ceramic powder and increase the powder's ability to adhere to polyethylene glycol-600, polyethylene glycol-2000, polymethyl methacrylate, etc.; polyethylene glycol-2000 is used as a hot melt adhesive to increase the powder's rapid re-wetting ability and improve the powder loading capacity; polyethylene glycol-4000 is used as an adhesive to increase the green body bonding strength and prevent the green body from breaking and being damaged; polymethyl methacrylate and polyvinylpyrrolidone are used as skeleton support materials to prevent the green body from deforming during the forming process.

[0023] Preferably, the printing parameters of the fused deposition printing technology include:

[0024] The nozzle diameter is 0.5-0.8 mm, the slice thickness is 0.4-0.8 mm, the printing flow rate is 90-110% f, the printing speed is 90-130% v, and the printing temperature is 130-160℃.

[0025] The beneficial effects of the preferred embodiment are that by setting the printing parameters to control the printing melt viscosity, combined with the formula system of the premix, the interlayer bonding strength of the green body obtained by printing can be improved, the interlayer bonding force can be increased, and it is beneficial to prepare a silicon nitride sandwich radome with diversified structure and good mechanical properties.

[0026] Preferably, the heating treatment includes water bath heating of the silicon nitride radome green body, the heating temperature is 70-90℃, and the heating time is 24-48h. Through the heating treatment, the water-based components in the green body are removed.

[0027] Preferably, the sintering treatment includes:

[0028] First stage: increase the temperature from room temperature to 1300-1400℃ at a heating rate of 150-180℃ / h under a pressure of 0.5-2MPa, and keep the temperature for 1-3h;

[0029] Second stage: increase the temperature from the holding temperature of the first stage to 1550-1650℃ at a heating rate of 180-240℃ / h under a pressure of 2-4MPa, and keep the temperature for 2-4h.

[0030] The beneficial effect of the preferred scheme is that the first stage crystal realizes pre-growth, and the second stage realizes complete phase change, so that a low-deformation and high-precision silicon nitride sandwich antenna cover is obtained.

[0031] The application also discloses a silicon nitride sandwich antenna cover prepared by the preparation method.

[0032] Compared with the prior art, the beneficial effect of the application is that the silicon nitride implant blank prepared by the preparation method has strong interlayer bonding force and has the advantages of structural diversification and light weight. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The application also discloses a silicon nitride sandwich antenna cover prepared by the preparation method. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the embodiments of the application will be clearly and completely described below in combination with the embodiments of the application.

[0035] Embodiment 1

[0036] The embodiment provides a preparation method of a silicon nitride sandwich antenna cover, and the preparation method comprises the following steps:

[0037] S1: 85 parts of silicon nitride powder with an average particle size of 0.5 um, 10 parts of lanthanum oxide and 5 parts of magnesium oxide are taken, mixed with a solvent ethanol, and grinded in a ball mill for 15 hours to obtain ceramic slurry with a particle size D 50 ≤0.5um;

[0038] The ceramic slurry is dried in an oven at 70 DEG C for more than 24 hours until the weight is constant, and then sieved through a 60-mesh sieve to obtain ceramic powder.

[0039] S2: 75 parts of the ceramic powder are mixed with polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinyl pyrrolidone, a dispersing agent, a plasticizer and a polymerization inhibitor in a banbury mixer at 160 DEG C for 4 hours to obtain a mixture;

[0040] The dispersing agent is oleic acid OA, the plasticizer is dibutyl phthalate DBP, and the polymerization inhibitor is phenothiazine. The total weight of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinyl pyrrolidone, the dispersing agent, the plasticizer and the polymerization inhibitor is 25 parts. Specifically, the weight ratio of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinyl pyrrolidone, the dispersing agent, the plasticizer and the polymerization inhibitor is 15:40:15:10:15:1.9:3:0.1.

[0041] S3: cooling and granulating the mixture to obtain a premix.

[0042] S4: printing the premix by a fused deposition printing technology to obtain a silicon nitride radome blank. The diameter of the printer nozzle is 0.5 mm, the slice thickness is 0.4 mm, the printing flow is 90% f, the printing speed is 90% v, and the printing temperature is 130°C.

[0043] S5: placing the silicon nitride radome blank in a steaming oven at 70°C and heating and steaming for 48 h to remove the water-based components, thereby obtaining a radome blank.

[0044] S6: performing a gas pressure sintering treatment on the radome blank to obtain a silicon nitride sandwich radome; comprising:

[0045] First stage: increasing the temperature from room temperature to 1350°C at a rate of 150°C / h under a pressure of 2 MPa, and holding for 1 h to pre-grow the crystals;

[0046] Second stage: increasing the temperature from 1350°C to 1550°C at a rate of 180°C / h under a pressure of 4 MPa, and holding for 4 h.

[0047] Example 2

[0048] The embodiment provides a preparation method of a silicon nitride sandwich radome, comprising the following steps:

[0049] S1: taking 88 parts by weight of silicon nitride powder with an average particle size of 1 μm, 4 parts of bauxite, 3 parts of lanthanum oxide, 5 parts of magnesium oxide, and a solvent ethanol, mixing and grinding in a ball mill for 15 h to obtain a ceramic slurry with a particle size D 50 ≤0.5um;

[0050] The ceramic slurry is dried in an oven at 60°C for more than 30 h to a constant weight, and then sieved through a 60-mesh sieve to obtain a ceramic powder.

[0051] S2: placing 80 parts of the ceramic powder and polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, a dispersing agent, a plasticizer, and a polymerization inhibitor in a banbury mixer at 170°C, and mixing and kneading for 3.5 h to obtain a mixture;

[0052] The dispersant is oleic acid OA, the plasticizer is dibutyl phthalate DBP, and the polymerization inhibitor is phenothiazine. The weight parts of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinyl pyrrolidone, dispersant, plasticizer, and polymerization inhibitor account for 20 parts in total. Specifically, the weight parts of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinyl pyrrolidone, dispersant, plasticizer, and polymerization inhibitor are in a ratio of 15:35:10:15:20:2.8:2:0.2.

[0053] S3: cooling and granulating the mixture to obtain a premix.

[0054] S4: printing the premix by a fused deposition printing technology to obtain a silicon nitride radome blank. The diameter of the printer nozzle is 0.6 mm, the slicing thickness is 0.6 mm, the printing flow is 100% f, the printing speed is 110% v, and the printing temperature is 145°C.

[0055] S5: placing the silicon nitride radome blank in a steaming oven at 80°C for heating and steaming for 36 h to remove the water-based components, thereby obtaining a radome blank.

[0056] S6: performing a gas pressure sintering treatment on the radome blank to obtain a silicon nitride sandwich radome; including:

[0057] First stage: increasing the temperature from room temperature to 1300°C at a rate of 170°C / h under a pressure of 1 MPa, and keeping the temperature for 3 h to pre-grow the crystal;

[0058] Second stage: increasing the temperature from 1300°C to 1600°C at a rate of 210°C / h under a pressure of 3 MPa, and keeping the temperature for 3 h.

[0059] Example 3

[0060] The embodiment provides a preparation method of a silicon nitride sandwich radome, including the following steps:

[0061] S1: taking 91 parts of silicon nitride powder with an average particle size of 2 μm, 5 parts of bauxite, 2 parts of lanthanum oxide, and 2 parts of magnesium oxide by weight, mixing with a solvent ethanol, grinding and mixing in a ball mill for 15 h to obtain a ceramic slurry with a particle size D 50 ≤0.5um;

[0062] The ceramic slurry is dried in an oven at 80°C for more than 24 h to a constant weight, and then sieved through a 60-mesh sieve to obtain a ceramic powder.

[0063] S2: 85 parts of ceramic powder is mixed with polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, dispersant, plasticizer, polymerization inhibitor in a banbury mixer at 180℃ for 3h to obtain a mixture;

[0064] The dispersant is oleic acid OA, the plasticizer is dibutyl phthalate DBP, and the polymerization inhibitor is phenothiazine. The total weight of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, dispersant, plasticizer, and polymerization inhibitor is 15 parts. Specifically, the weight ratio of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, dispersant, plasticizer, and polymerization inhibitor is 15:30:5:20:25:3.5:1:0.5.

[0065] S3: The mixture is cooled and granulated to obtain a premix.

[0066] S4: The premix is printed by a fused deposition printing technology to obtain a silicon nitride radome blank. The printer nozzle diameter is 0.8mm, the slicing thickness is 0.8mm, the printing flow is 110%f, the printing speed is 130%v, and the printing temperature is 160℃.

[0067] S5: The silicon nitride radome blank is heated and cooked in a steaming box at 90℃ for 24h to remove the water-based ingredients, and a radome blank is obtained.

[0068] S6: The radome blank is subjected to a gas pressure sintering process to obtain a silicon nitride sandwich radome; comprising:

[0069] First stage: at a heating rate of 180℃ / h, the temperature is raised from room temperature to 1400℃ under a pressure of 0.5MPa, and the crystal is pre-grown for 3h;

[0070] Second stage: at a heating rate of 240℃ / h, the temperature is raised from 1400℃ to 1650℃ under a pressure of 2MPa, and the temperature is maintained for 2h.

[0071] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; based on the examples of the present application, all other examples obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions described in the foregoing examples, or make equivalent replacements to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of manufacturing a silicon nitride interlayer radome, characterized by, The preparation method comprises the following steps: S1: mixing silicon nitride powder, sintering aid and solvent, and drying to obtain ceramic powder, wherein the drying temperature of the drying treatment is 60-80℃, and the drying time is not less than 24h; S2: mixing the ceramic powder with polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, dispersant, plasticizer and polymerization inhibitor to obtain a mixture, wherein the ceramic powder accounts for 75-85 parts by weight, and the other components together account for 15-25 parts by weight; the dispersant comprises oleic acid OA, the plasticizer comprises dibutyl phthalate DBP, and the polymerization inhibitor is phenothiazine; the weight ratio of polyethylene glycol-600, polyethylene glycol-2000, polyethylene glycol-4000, polymethyl methacrylate, polyvinylpyrrolidone, dispersant, plasticizer and polymerization inhibitor is (10-20):(30-40):(5-15):(10-20):(15-25):(1.9-3.5):(1-3):(0.1-0.5); the mixing method of the mixture is internal mixing, the internal mixing temperature is 160-180℃, and the internal mixing time is not less than 3h; S3: cooling and granulating the mixture to obtain premix; S4: printing the premix by using a fused deposition printing technology to obtain a silicon nitride radome blank; S5: performing heating treatment on the silicon nitride radome blank to obtain a radome blank; S6: performing sintering treatment on the radome blank to obtain a silicon nitride sandwich radome; the sintering treatment comprises: first stage: increasing the temperature from room temperature to 1300-1400℃ at a temperature increasing rate of 150-180℃ / h under a pressure of 0.5-2MPa, and keeping the temperature for 1-3h; second stage: increasing the temperature from the temperature keeping temperature of the first stage to 1550-1650℃ at a temperature increasing rate of 180-240℃ / h under a pressure of 2-4MPa, and keeping the temperature for 2-4h.

2. The method of claim 1, wherein the silicon nitride interlayer is formed by a plasma enhanced chemical vapor deposition method. the silicon nitride powder accounts for 85-91 parts by weight, and the sintering aid accounts for 9-15 parts by weight; the average particle size of the silicon nitride powder is 0.5-2μm.

3. The method of claim 1, wherein the silicon nitride interlayer radome is prepared by the steps of: the sintering aid comprises any one or more of lanthanum oxide, magnesium oxide and bismuth oxide.

4. The method of claim 1, wherein the method further comprises: the heating treatment comprises: performing water bath heating on the silicon nitride radome blank, the heating temperature is 70-90℃, and the heating time is 24-48h.

5. A silicon nitride sandwiched radome, characterized by, The silicon nitride sandwich radome is prepared by using the preparation method in any one of claims 1-4.

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