CN115073195B - Silicon nitride whisker reinforced nitride composite material for 3D printing radar antenna housing and preparation and printing methods - Google Patents

Silicon nitride whisker reinforced nitride composite material for 3D printing radar antenna housing and preparation and printing methods Download PDF

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CN115073195B
CN115073195B CN202210626822.5A CN202210626822A CN115073195B CN 115073195 B CN115073195 B CN 115073195B CN 202210626822 A CN202210626822 A CN 202210626822A CN 115073195 B CN115073195 B CN 115073195B
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powder
printing
antenna housing
radome
whisker
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CN115073195A (en
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叶昉
成来飞
许泽水
吕鑫元
张立同
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Northwestern Polytechnical University
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Abstract

The invention relates to a silicon nitride whisker reinforced nitride composite material for a 3D printing radar radome and a preparation method and a printing method thereof 3 N 4w Preparing high-strength Si from the slurry through spray granulating 3 N 4w And mixing the composite microspheres with the Si powder mechanically to obtain powder for subsequent 3D printing. According to the radar antenna housing three-dimensional model, a biscuit is formed by adopting a powder 3D printing technology, after printing is completed, sequentially carrying out curing, powder removing, vacuum carbonization, si powder in-situ nitridation and other treatments on the biscuit, thereby obtaining Si with certain structural strength and excellent wave-transmitting performance 3 N 4 And (3) preparing a whisker preform. According to the using requirements, a nitride matrix can be further prepared in the prefabricated body, and the silicon nitride whisker reinforced nitride composite material radome with more excellent mechanical properties is obtained. The method realizes net size molding of the large-size radar antenna housing with the complex profile, and has the advantages of high process reliability, short preparation period and low cost.

Description

Silicon nitride whisker reinforced nitride composite material for 3D printing radar antenna housing and preparation and printing methods
Technical Field
The invention belongs to the technical field of radome preparation, and relates to a silicon nitride whisker reinforced nitride composite material for a 3D printing radome, and a preparation method and a printing method thereof.
Background
With the rapid development of high-Mach aircraft, the harsh working environment of the aircraft provides higher comprehensive performance requirements on the radar antenna housing used for communication at the tip of the aircraft, such as high temperature resistance, wave transmission, high strength, vibration resistance, thermal shock resistance and the like, specifically, the service temperature of the antenna housing is more than 1600 ℃, the wave transmission rate is more than 75 percent, the bending strength of the antenna housing material is more than 80MPa, and the fracture toughness is more than 3 MPa.m 1/2 And the like. Traditional quartz ceramics,Thermal wave-transmitting materials such as alumina ceramics and phosphates cannot meet the working requirement of high-Mach number aircrafts, and development of novel high-performance thermal wave-transmitting materials and a preparation technology of an antenna housing thereof is urgently needed.
The nitride material has the advantages of high temperature resistance, excellent high-temperature mechanical property, moderate dielectric constant, corrosion resistance and the like, and is an ideal candidate material for the high-Mach-number aircraft radome. In the developed nitride systems, silicon nitride (Si) 3 N 4 ) Compared with Boron Nitride (BN), the Boron Nitride (BN) has higher strength and modulus, better oxidation resistance and rain erosion resistance and more application potential.
Si developed at present 3 N 4 In the system antenna cover material, with dense Si 3 N 4 Ceramic phase comparison, using Si 3 N 4 The fiber or whisker reinforced nitride ceramic matrix composite has the advantages of low dielectric constant, good wave-transmitting performance, easy processing and near net size molding; with porous Si 3 N 4 Ceramic phase comparison, using Si 3 N 4 The fiber or whisker reinforced nitride ceramic matrix composite has the advantages of high strength, good toughness, moisture absorption resistance, ablation resistance and the like. Further, si is used 3 N 4 The microstructure and phase composition of the fiber or whisker reinforced nitride ceramic matrix composite material are high in designability. Patent CN111285694A discloses a high-temperature wave-transparent continuous Si 3 N 4 Fiber reinforced Si 3 N 4 Ceramic matrix composite (Si) 3 N 4f /Si 3 N 4 ) The preparation method of the antenna housing adopts Si 3 N 4 Fiber as reinforcement, chemical Vapor Infiltration (CVI) combined with precursor impregnation cracking (PIP) process for preparing Si 3 N 4 The base body and the antenna cover are designed into a split structure, so that the antenna cover has higher ablation resistance when being in service in a severe environment. But is limited by Si 3 N 4 The thermal stability of the fiber, and the antenna housing prepared by the method is only suitable for the working environment below 1300 ℃. Patent CN 111320484A discloses isotropic Si 3 N 4 Whisker reinforced nitride ceramic matrix composite (Si) 3 N 4w Nitride) antenna housing. The method is firstFirstly, the design and the manufacture of a gel injection mold are finished according to the geometric dimension of the antenna housing, and then a gel injection molding process is adopted to form Si 3 N 4 And (3) preparing a whisker preform. After drying and degumming, preparing a nitride matrix in the preform by a PIP process, and finally obtaining isotropic Si through oxidation decarbonization and finish machining 3 N 4w The/nitride composite material antenna housing. The method can realize the near net size molding of the antenna housing, and the manufactured antenna housing can meet the high-temperature service requirement. However, the customized gel-casting mold increases economic cost, and in addition, the process steps of demolding, glue discharging, finishing and the like are included, so that the time cost is also improved.
The additive manufacturing (commonly known as 3D printing) technology is a novel ceramic biscuit forming process, has the advantages of low cost, stable process, no need of post-processing of products and the like, has remarkable advantages in the aspect of preparing components with complex structures and special profiles, and has the potential to be applied to forming of ceramic radomes. Patent CN 111244628A discloses a high temperature resistant wide band wave-transparent ceramic radome structure and preparation method thereof, and it adopts ultraviolet curing 3D printing technique to prepare the radome structure, through the thickness of regulation and control homogeneity outer layer, homogeneity inlayer, porous layer and the diameter and the hole interval of hole, obtains the radome structure that satisfies different wave-transparent needs. The method comprises the following specific steps: the method comprises the steps of firstly measuring the shrinkage rate of a sintered 3D printing ceramic material test piece, amplifying an antenna housing model according to the measured shrinkage rate to form a printing model, then preparing photocuring resin, ceramic powder (quartz or silicon nitride), a dispersing agent and a photoinitiator into slurry, then forming a complete ceramic blank on ceramic photocuring 3D printing equipment through layer-by-layer superposition according to the printing model, and finally degreasing and sintering after the ceramic blank is obtained to obtain the high-temperature-resistant broadband wave-transparent antenna housing. The above method has the following features: (1) After the resin is cured, the strength of the ceramic biscuit can be ensured, so that the resin content in the prepared slurry cannot be too low, the distribution cannot be too dispersed, otherwise, the ultraviolet curing effect is insufficient, the ceramic powder cannot be connected into a framework through the resin, and the biscuit formability is influenced. Meanwhile, certain requirements are provided for the solid content of the ceramic powder in the prepared slurry; (2) Ceramic blankAfter printing is finished, degreasing is needed to remove organic matters in the blank; (3) The ceramic antenna housing is prepared by sintering after the green body is degreased, volume shrinkage can be generated in the sintering process, and the net size forming control difficulty of the component is high. Based on the characteristics, the feasibility of manufacturing the silicon nitride radome by adopting the method is preliminarily analyzed, and the following findings are found: (1) Because the radome ceramic body is generally a hollow structure, the ceramic body may collapse after degreasing; (2) Si 3 N 4 The compound is a covalent bond compound, is difficult to sinter, and needs to be added with a sintering aid to improve the sintering property. However, the sintering aid is usually a low-melting oxide, which is present in Si 3 N 4 The grain boundary can have adverse effect on the high-temperature performance of the ceramic; (3) Si 3 N 4 The shrinkage is serious in the ceramic sintering process (the linear shrinkage rate is generally between 10 and 25 percent), and the difficulty in controlling the size and the profile is high. In conclusion, the analysis shows that the Si is prepared by adopting the ultraviolet curing 3D printing technology 3 N 4 The ceramic radome of the system has great difficulty.
As described above, the continuous fiber woven Si 3 N 4f /Si 3 N 4 Composite material antenna housing and gel casting Si 3 N 4w The nitride composite material antenna housing and the ultraviolet curing 3D printing ceramic antenna housing have some defects and limitations in the aspects of performance, process, manufacturing period, cost and the like, and the strict requirements of the performance and the process performance of the antenna housing of the hypersonic aircraft are difficult to meet at the same time. Therefore, the development of a short-cycle, low-cost and reliable preparation technology of the high-performance nitride system radome is urgently needed.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a silicon nitride whisker reinforced nitride composite material for a 3D printing radar antenna housing and preparation and printing methods thereof, and aims to solve the problems of Si in the prior art 3 N 4 Insufficient temperature resistance of fiber-reinforced ceramic matrix composite antenna housing and preparation of Si by gel casting 3 N 4w The nitride composite material antenna housing mold has the advantages of high processing cost, long process period and sintering tool for ultraviolet curing 3D printing ceramic antenna housingThe process has the problems of shrinkage, high preparation difficulty and the like. The high-temperature-resistant wave-transparent bearing integrated antenna housing can be manufactured in a low-cost, short-period and net size mode under the condition that a die is not used.
Technical scheme
The silicon nitride whisker reinforced nitride composite material for the 3D printing radar antenna housing is characterized by comprising the following components in parts by mass: 9.1 to 28.6 percent of surface modified Si powder and 71.4 to 90.9 percent of Si 3 N 4w -Si composite microspheres, and then 9.1-28.6% of acrylamide and 1.5-9.5% of methylene bisacrylamide by taking the two as the total mass; the surface modified Si powder is formed by a layer of SiO with uniform thickness on the surface of Si powder 2 And (3) a layer.
Said Si 3 N 4w the-Si composite microspheres are 26-68% of Si in mass fraction 3 N 4w Granulating mixed solution of-Si powder and 32-74% of premixed liquid to obtain Si 3 N 4w -Si composite microspheres; the premixed liquid comprises 80-90% of deionized water, 6-17% of dextrin, 0.2-2% of polyethylene glycol, 2-10% of tetramethylammonium hydroxide aqueous solution and 0.5-2% of ammonium polyacrylate aqueous solution in percentage by mass; said Si 3 N 4w -Si in mass fraction in the Si powder 3 N 4 The crystal whisker accounts for 83.3 to 90.9 percent, and the Si powder accounts for 9.1 to 16.7 percent.
SiO on the surface of the Si powder 2 The thickness of the layer is 20 to 100nm.
Said Si 3 N 4w The grain size distribution of the-Si composite microspheres is 10-100 mu m.
A method for preparing the silicon nitride whisker reinforced nitride composite material for the 3D printing radome is characterized by comprising the following steps of:
step 1, surface modification of Si powder: heat treating Si powder of 1-3 micron size at 700-1200 deg.c in air atmosphere for 1-10 hr to form one layer of SiO layer of homogeneous thickness on the surface of the Si powder 2 A layer;
step 2, preparing Si 3 N 4w -Si slurry: by mass fraction, 80-90 percent ofDeionized water, 6 to 17 percent of dextrin, 0.2 to 2 percent of polyethylene glycol, 2 to 10 percent of tetramethyl ammonium hydroxide aqueous solution and 0.5 to 2 percent of polyacrylic ammonium aqueous solution are prepared into premixed solution;
by mass fraction, 32-74% of premixed liquid and 26-68% of Si 3 N 4w Mixing the-Si powder to obtain Si 3 N 4w -a Si slurry; said Si 3 N 4w -the Si powder comprises, in mass fraction: 83.3 to 90.9% of Si 3 N 4 Crystal whiskers and 9.1% -16.7% of Si powder treated in the step 1;
in Si 3 N 4w ZrO addition to Si slurries 2 Ball milling beads, wherein the mass ratio of the ball milling beads to the slurry is (3-5): 1, the ball milling beads are subjected to ball milling mixing in a horizontal ball mill, the ball milling rotation speed is 40-80 r/min, and the ball milling time is 8-36 h;
step 3, preparation of Si 3 N 4w -Si composite microspheres: mixing Si 3 N 4w Putting the Si slurry into a spray dryer for granulation, wherein the air inlet temperature is 180-220 ℃, the air outlet temperature is 60-80 ℃, the slurry flow is 10-40 mL/min, the rotation speed of an atomizing disc is 6000-24000 r/min, and collecting to obtain the Si slurry 3 N 4w -Si composite microspheres;
step 4, mixing and printing powder: according to the mass fraction, 71.4 to 90.9 percent of Si obtained in the step 3 is added 3 N 4w And (2) mixing the-Si composite microspheres with 9.1-28.6% of the Si powder obtained in the step (1) to obtain silicon nitride whisker reinforced nitride composite material powder for the 3D printing radar antenna housing.
The mass fraction of the tetramethylammonium hydroxide aqueous solution is more than 25%.
The mass fraction of the ammonium polyacrylate aqueous solution is more than 40%.
A method for 3D printing of a radome by using the silicon nitride whisker reinforced nitride composite material for the 3D printing of the radome is characterized by comprising the following steps:
step 1): with Si 3 N 4w Taking the total mass of the-Si composite microspheres and the Si powder as a reference, adding 9.1-28.6% of acrylamide and 1.5% >, based on the total mass9.5 percent of methylene bisacrylamide, and mechanically mixing the prepared powder in a horizontal ball mill for 1-4 hours to obtain uniformly mixed powder;
step 2), 3D printing the antenna housing: filling the uniformly mixed powder into a powder box of a powder printer, and starting to print an antenna housing biscuit; wherein, the thickness of the powder layer is 0.1mm, and the saturation of the binder is 100%/200% -170%/340%; the adhesive is ammonium persulfate aqueous solution;
step 3), heating, crosslinking and curing: transferring the printed radome biscuit into a forced air drying oven for crosslinking and curing, wherein the crosslinking temperature is 60-100 ℃, and the crosslinking time is 20-120 min;
step 4), biscuit powder removal: removing excessive Si on the outer surface and the inner side of the completely solidified antenna housing 3 N 4w -Si powder to obtain a de-powderized radome biscuit;
step 5), vacuum carbonization: transferring the radome biscuit obtained in the step 7 into a well type vacuum furnace, keeping the vacuum degree in the furnace below 0.01MPa, raising the temperature to 700-1000 ℃ at the heating rate of 3-10 ℃/min, and preserving the temperature for 1-3 h to convert acrylamide and methylene bisacrylamide into pyrolytic carbon;
step 6), nitriding of Si powder: after the heat preservation is finished, introducing nitrogen into the well type vacuum furnace to normal pressure, wherein the flow rate of the nitrogen is 20-200 mL/min, keeping the flow rate of the nitrogen unchanged, raising the temperature to 1300-1400 ℃ at the heating rate of 3-10 ℃/min, raising the temperature to 1400-1500 ℃ at the heating rate of 1-3 ℃/min, preserving the heat for 1-3 h, reacting Si powder with the nitrogen, and generating Si in situ 3 N 4 Obtaining the antenna housing with the secondary pore characteristics; the secondary pores refer to Si 3 N 4 Submicron-scale pores and Si between crystal grains in whisker microsphere 3 N 4 Micron-sized pores among the whisker microspheres.
After the radome with the secondary pore characteristics is completed in the step 6), if the mechanical property of the radome needs to be further improved, a nitride matrix with a certain content is prepared in the radome with the secondary pore characteristics obtained in the step 9 by adopting a combined process of a Chemical Vapor Infiltration (CVI) method and a Precursor Impregnation Pyrolysis (PIP) method.
The nitride matrix comprises Si 3 N 4 Boron Nitride (BN), silicon boron nitrogen (SiBN), silicon aluminum oxygen nitrogen (SiAlON), silicon nitrogen oxygen (Si) 2 N 2 O), and a complex phase matrix of any two, three, four or five of the above.
The sequence of the combined process is as follows: firstly, si is prepared by adopting a CVI method 3 N 4 The substrate is then PIP-prepared to Si 3 N 4 Matrix in which Si is prepared by CVI 3 N 4 The duration of the matrix is 60-120 h (i.e. 1-2 heats), and the PIP method is used for preparing Si 3 N 4 The heat of the substrate is 2-3 times.
In the step 10, the volume fraction of the nitride matrix is 40% -65%, and Si is present 3 N 4w The porosity of the/nitride composite material antenna housing is 15% -30%.
The mechanical mixing of step 1) is carried out without adding ball milling beads.
In the step 6), siO on the surface of the Si powder 2 Layer and pyrolytic carbon obtained in step 5) is in N 2 The carbothermal reduction nitridation reaction can occur under the atmosphere to generate Si 3 N 4 While removing residual carbon and generated Si 3 N 4 Has porous characteristic.
In the step 6), the Si powder is melted at the temperature close to the melting point, and is mixed with N 2 Si generated by in situ reaction 3 N 4 Or coated with Si 3 N 4 On the surface of whiskers, or distributed over Si 3 N 4 Between whiskers, or in Si 3 N 4 Inside the whisker microsphere and between the microspheres.
The secondary pores refer to Si 3 N 4 The submicron level between crystal grains in the whisker microsphere is 20-600 nm; pores and Si 3 N 4 The micron-sized pores between the whisker microspheres are 1-30 mu m.
The acrylamide and the methylene bisacrylamide need to be sieved by a 150-mesh sieve.
Advantageous effects
The invention provides a silicon nitride whisker reinforced nitride composite material for a 3D printing radar radome and a preparation method and a printing method thereofPre-oxidizing silicon (Si) powder and preparing Si 3 N 4w Preparing high-strength Si from the uniformly mixed slurry by spray granulation 3 N 4w And mixing the composite microspheres with the Si powder mechanically to obtain powder for subsequent 3D printing. According to the radome three-dimensional model, a biscuit is formed by adopting a powder 3D printing technology, and after printing is finished, the biscuit is sequentially subjected to curing, powder removal, vacuum carbonization, si powder in-situ nitridation and the like, so that Si with certain structural strength and excellent wave transmission performance is obtained 3 N 4 And (3) preparing a whisker preform. According to the use requirement, the nitride (including Si) can be further prepared in the prefabricated body 3 N 4 BN, siBN, siAlON and Si 2 N 2 O, etc.) to obtain the silicon nitride whisker reinforced nitride composite material radome with more excellent mechanical property. The method can realize net size molding of the large-size radar antenna housing with the complex profile, and has the advantages of high process reliability, short preparation period and low cost. The radome prepared by the method has the characteristics of high temperature resistance, excellent mechanical and wave-transmitting properties and the like, and can meet the working requirements of high-Mach number aircrafts.
The beneficial effects of the invention are:
(1) The nitride composite material radome prepared based on the powder 3D printing technology has the advantages of high preparation precision, low preparation cost, short process period, no need of a mold and subsequent processing, simple process, high repeatability and the like.
(2) Adopting a one-dimensional single crystal structure Si 3 N 4 The crystal whisker as the reinforcement of the nitride composite material has the following advantages: (1) the single crystal material has excellent high temperature resistance (the inert atmosphere is more than 1700 ℃); (2) the single crystal material has excellent mechanical properties (high strength, modulus, hardness and the like); (3) the length-diameter ratio of the whisker is moderate, and a prefabricated body and a composite material formed by the whisker have isotropic characteristics.
(3)Si 3 N 4 The crystal whisker has excellent dispersibility in an alkaline environment, and Si powder is easy to react in the alkaline environment to generate silicate. To mix Si 3 N 4 Preparing crystal whisker and Si powderMixing the slurry, and carrying out surface modification on the Si powder. Generating thin SiO layer on the surface after pre-oxidation of Si powder 2 Can effectively slow down the reaction rate of the Si powder in the alkaline environment, improve the stability of the Si powder in the alkaline slurry and provide a way for the subsequent preparation of Si 3 N 4w the-Si composite microspheres lay a foundation.
(4) Acrylamide and methylene bisacrylamide are used as the adhesive for printing powder, so that the strength of the biscuit of the powder 3D printing radome can be effectively improved, and the biscuit is prevented from collapsing in the powder removal stage.
(5) A small amount of pyrolytic carbon formed after vacuum carbonization of crosslinked and cured acrylamide and methylene bisacrylamide can be preoxidized with Si powder to form SiO on the surface 2 Reacting under nitrogen atmosphere to generate Si 3 N 4 And the gas can also be directly reacted with nitrogen to be removed, so that the adverse effect of the pyrolytic carbon on the wave transmission performance of the antenna housing is avoided.
(6) Heating to 1300-1400 ℃ at a heating rate of 3-10 ℃/min, so that SiO on the surface of the Si powder can be obtained 2 The layer is preferentially and fully subjected to carbothermic reduction nitridation reaction with residual carbon to generate porous Si on the surface of Si powder 3 N 4 And (3) a layer. Subsequently, the temperature is raised to 1400-1500 ℃ at the heating rate of 1-3 ℃/min, and the temperature is kept for 1-3 h, so that the porous Si can be obtained 3 N 4 The Si powder in the layer and nitrogen gas are subjected to nitridation reaction to generate Si in situ 3 N 4 The selection and the regulation of the heating rate and the temperature can ensure the sufficient nitridation of the Si powder, and the strength of the antenna housing obtained in the step 9 can be improved.
(7) Nitriding of Si powder to produce Si 3 N 4 And (4) the strength improvement of the antenna housing obtained in the step (9) is facilitated. On the one hand, si 3 N 4 Si generated by Si powder reaction in the whisker microsphere 3 N 4 The bonding strength among the whiskers is improved; on the other hand, si 3 N 4 Si generated by Si powder reaction between whisker microspheres 3 N 4 The bonding between the microspheres is enhanced.
(8) The invention provides a method for further preparing a nitride matrix in the antenna housing to regulate and control the mechanical and wave-transmitting properties of the antenna housing. From Si 3 N 4 Ceramic bone formed by whisker microsphereThe frame has the structural characteristics of secondary pores, is matched with a CVI and PIP combined process, firstly adopts a CVI method to prepare a small amount of matrix to fill small pores of the spherical wall, then adopts a PIP method to prepare a part of matrix with a certain content to fill large pores among the spheres, regulates and controls the porosity, density, mechanics and wave-transparent performance of the radome, and meets different application requirements.
Drawings
FIG. 1 is Si used in the present invention 3 N 4 The micro-morphology of the whiskers.
FIG. 2 shows Si prepared according to the present invention 3 N 4w -micro-morphology of Si composite microspheres.
FIG. 3 shows Si formed by 3D powder printing according to the present invention 3 N 4w Macroscopic photograph of the Si radome biscuit (before nitriding).
FIG. 4 shows Si produced by the present invention 3 N 4w The microstructure of the radome wall of the nitride composite material radome.
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
example 1
Step 1: surface modification of Si powder: heat treating Si powder with 3 micron grain size at 1000 deg.c in air atmosphere for 3 hr to form one layer of SiO with thickness of 80nm on the surface of the Si powder 2 A layer;
step 2: preparation of Si 3 N 4w -Si slurry: preparing a premixed solution by using 81% of deionized water, 10% of dextrin (binder), 1% of polyethylene glycol (plasticizer), 6% of tetramethylammonium hydroxide aqueous solution (the mass fraction is more than 25%, pH regulator) and 2% of ammonium polyacrylate aqueous solution (the mass fraction is more than 40%, dispersant) in terms of mass fraction for later use;
mixing 40% of premixed solution and 60% of Si in percentage by mass 3 N 4w Mixing the-Si powder to obtain Si 3 N 4w -a Si slurry. Si as mentioned above 3 N 4w the-Si powder contains Si 3 N 4 Whiskers and the Si powder treated in the step 1, wherein the Si is calculated by mass fraction 3 N 4 84% of whisker and 16% of Si powder;
adding into the above slurryInto ZrO 2 Ball milling beads, wherein the mass ratio of the ball milling beads to the slurry is 3;
and step 3: preparation of Si 3 N 4w -Si composite microspheres: uniformly and stably adding Si obtained in the step 2 3 N 4w Granulating the-Si slurry in a spray dryer, wherein the air inlet temperature is 200 ℃, the air outlet temperature is 80 ℃, the slurry flow is 30mL/min, the rotating speed of an atomizing disc is 24000r/min, and collecting to obtain Si 3 N 4w -Si composite microspheres;
and 4, step 4: mixing printing powder: by mass fraction, 80% of Si obtained in the step 3 3 N 4w mixing-Si composite microspheres with 20% of Si powder obtained in the step 1;
with Si 3 N 4w Taking the total mass of the Si composite microspheres and the Si powder as a reference, adding 10% of acrylamide and 3.3% of methylene bisacrylamide by mass, and mechanically mixing the prepared powder in a horizontal ball mill for 2 hours;
and 5:3D printing antenna housing: and (4) filling the uniformly mixed powder obtained in the step (4) into a powder box of a powder printer, and starting to print the radome biscuit. Wherein the thickness of the powder layer is 0.1mm, and the saturation of the binder is 170%/340%;
step 6: heating, crosslinking and curing: the printed radome biscuit (containing excessive Si on the inner surface and the outer surface) 3 N 4w -Si powder) is transferred into a forced air drying oven for crosslinking and curing, the crosslinking temperature is 80 ℃, and the crosslinking time is 40min;
and 7: biscuit powder removal: removing excessive Si on the outer surface and the inner side of the completely solidified antenna housing 3 N 4w -Si powder;
and 8: vacuum carbonization: transferring the antenna housing obtained in the step (7) into a well type vacuum furnace, keeping the vacuum degree in the furnace below 0.01MPa, raising the temperature to 900 ℃ at the heating rate of 5 ℃/min, and preserving the temperature for 2 hours to convert acrylamide and methylene bisacrylamide into pyrolytic carbon;
and step 9: nitriding of Si powder: after the heat preservation in the step 8 is finished, the mixture is fed into a well type vacuum furnaceIntroducing nitrogen to normal pressure, wherein the nitrogen flow is 100mL/min, keeping the nitrogen flow unchanged, raising the temperature to 1390 ℃ at the temperature raising rate of 5 ℃/min, raising the temperature to 1450 ℃ at the temperature raising rate of 3 ℃/min, and preserving the temperature for 2h to enable Si powder and nitrogen to react to generate Si in situ 3 N 4 ；
Step 10: si 3 N 4 Preparing a matrix: sequentially preparing Si in the radome with the secondary pore characteristics obtained in the step 9 by adopting a combined process of a CVI method and a PIP method 3 N 4 The substrate is prepared by 2 times of CVI method, 120h of codeposition, 3 times of PIP method, and compact Si is finally obtained 3 N 4w /Si 3 N 4 A composite material radome is provided.
Si prepared in this example 3 N 4w /Si 3 N 4 The porosity of the composite material antenna housing is 20%, and the composite material antenna housing has excellent mechanical properties. In addition, si produced by CVI method and PIP method 3 N 4 The matrix is amorphous, so that Si is prepared 3 N 4w /Si 3 N 4 The composite material antenna housing has excellent high-temperature wave-transmitting performance.
Example 2
Step 1: surface modification of Si powder: heat treating Si powder with particle size of 3 μm at 1200 deg.C in air atmosphere for 1h to form a layer of SiO with thickness of about 100nm on the surface of Si powder 2 A layer;
step 2: preparation of Si 3 N 4w -Si slurry: preparing 81% of deionized water, 10% of dextrin (binder), 1% of polyethylene glycol (plasticizer), 6% of tetramethylammonium hydroxide aqueous solution (mass fraction is more than 25%, pH regulator) and 2% of ammonium polyacrylate aqueous solution (mass fraction is more than 40%, dispersing agent) into a premixed solution by mass fraction for later use;
mixing 40% of premixed solution and 60% of Si in percentage by mass 3 N 4w Mixing the-Si powder to obtain Si 3 N 4w -a Si slurry. Si as above 3 N 4w the-Si powder contains Si 3 N 4 Crystal whisker and Si powder treated in the step 1, wherein the Si is calculated by mass fraction 3 N 4 90 percent of crystal whisker and 10 percent of Si powder；
Adding ZrO into the slurry 2 Ball milling beads, wherein the mass ratio of the ball milling beads to the slurry is 3;
and step 3: preparation of Si 3 N 4w -Si composite microspheres: uniformly and stably adding Si obtained in the step 2 3 N 4w Granulating the-Si slurry in a spray dryer, wherein the air inlet temperature is 200 ℃, the air outlet temperature is 80 ℃, the slurry flow is 30mL/min, the rotating speed of an atomizing disc is 24000r/min, and collecting to obtain Si 3 N 4w -Si composite microspheres;
and 4, step 4: mixing printing powder: by mass fraction, 90% of Si obtained in the step 3 3 N 4w mixing-Si composite microspheres with 10% of Si powder obtained in the step 1;
with Si 3 N 4w Taking the total mass of the Si composite microspheres and the Si powder as a reference, adding 10% of acrylamide and 3.3% of methylene bisacrylamide by mass, and mechanically mixing the prepared powder in a horizontal ball mill for 2 hours;
and 5:3D printing antenna housing: and (4) filling the uniformly mixed powder obtained in the step (4) into a powder box of a powder printer, and starting to print the radome biscuit. Wherein the thickness of the powder layer is 0.1mm, and the saturation of the binder is 170%/340%;
step 6: heating, crosslinking and curing: the printed radome biscuit (containing excessive Si on the inner surface and the outer surface) 3 N 4w -Si powder) is transferred into a forced air drying oven for crosslinking and curing, the crosslinking temperature is 80 ℃, and the crosslinking time is 40min;
and 7: biscuit powder removal: removing excessive Si on the outer surface and the inner side of the completely solidified antenna housing 3 N 4w -Si powder;
and 8: vacuum carbonization: transferring the antenna housing obtained in the step (7) into a well type vacuum furnace, keeping the vacuum degree in the furnace below 0.01MPa, raising the temperature to 900 ℃ at the heating rate of 5 ℃/min, and preserving the temperature for 2 hours to convert acrylamide and methylene bisacrylamide into pyrolytic carbon;
and step 9: si powderNitriding: after the heat preservation in the step 8 is finished, introducing nitrogen into the well type vacuum furnace to normal pressure, wherein the flow rate of the nitrogen is 100mL/min, keeping the flow rate of the nitrogen unchanged, raising the temperature to 1400 ℃ at the heating rate of 5 ℃/min, raising the temperature to 1450 ℃ at the heating rate of 3 ℃/min, preserving the heat for 2h, enabling Si powder and the nitrogen to react, and generating Si in situ 3 N 4 ；
Step 10: si 3 N 4 Preparing a matrix: sequentially preparing Si in the radome with the secondary pore characteristics obtained in the step 9 by adopting a combined process of a CVI method and a PIP method 3 N 4 The substrate is prepared by 2 times of CVI method, 120h of codeposition, 3 times of PIP method, and compact Si is finally obtained 3 N 4w /Si 3 N 4 A composite material radome is provided.
In this example, si was formulated in comparison with example 1 3 N 4w Increase of Si in case of-Si paste 3 N 4 The ratio of whisker to Si powder, and when mixing the printing powder, the Si content is increased 3 N 4w Ratio of-Si composite microsphere to Si powder, so that Si powder obtained in the nitriding process of Si powder in step 9 3 N 4 There are fewer substrates. Si of final preparation 3 N 4w /Si 3 N 4 The porosity of the composite material radome is 72%, the overall mechanical property of the radome is reduced compared with that of the radome in the embodiment 1, and the wave-transmitting performance of the radome is improved compared with that of the radome in the embodiment 1.
Example 3
Step 1: surface modification of Si powder: heat treating Si powder with particle size of 3 μm at 1000 deg.C in air atmosphere for 3 hr to form a layer of SiO with thickness of about 80nm on the surface of Si powder 2 A layer;
step 2: preparation of Si 3 N 4w -Si slurry: preparing a premixed solution by using 81% of deionized water, 10% of dextrin (binder), 1% of polyethylene glycol (plasticizer), 6% of tetramethylammonium hydroxide aqueous solution (the mass fraction is more than 25%, pH regulator) and 2% of ammonium polyacrylate aqueous solution (the mass fraction is more than 40%, dispersant) in terms of mass fraction for later use;
mixing 40% of premixed solution and 60% of Si in percentage by mass 3 N 4w mixing-Si powder to obtain Si 3 N 4w -a Si slurry. Si as above 3 N 4w the-Si powder contains Si 3 N 4 Crystal whisker and Si powder treated in the step 1, wherein the Si is calculated by mass fraction 3 N 4 84% of whisker and 16% of Si powder;
adding ZrO into the slurry 2 Ball milling beads, wherein the mass ratio of the ball milling beads to the slurry is 3;
and step 3: preparation of Si 3 N 4w -Si composite microspheres: uniformly and stably adding Si obtained in the step 2 3 N 4w Granulating the-Si slurry in a spray dryer, wherein the air inlet temperature is 200 ℃, the air outlet temperature is 80 ℃, the slurry flow is 30mL/min, the rotating speed of an atomizing disc is 24000r/min, and collecting to obtain Si 3 N 4w -Si composite microspheres;
and 4, step 4: mixing printing powder: by mass fraction, 80% of Si obtained in the step 3 3 N 4w mixing-Si composite microspheres with 20% of Si powder obtained in the step 1;
with Si 3 N 4w Taking the total mass of the Si composite microspheres and the Si powder as a reference, adding acrylamide accounting for 20% of the total mass and methylene bisacrylamide accounting for 6.7% of the total mass, and mechanically mixing the prepared powder in a horizontal ball mill for 2 hours;
and 5:3D printing antenna housing: and (4) filling the uniformly mixed powder obtained in the step (4) into a powder box of a powder printer, and starting to print the radome biscuit. Wherein the thickness of the powder layer is 0.1mm, and the saturation of the binder is 170%/340%;
step 6: heating, crosslinking and curing: the printed radome biscuit (containing excessive Si on the inner surface and the outer surface) 3 N 4w -Si powder) is transferred into a forced air drying oven for crosslinking and curing, the crosslinking temperature is 80 ℃, and the crosslinking time is 40min;
and 7: biscuit powder removal: removing excessive Si on the outer surface and the inner side of the completely solidified antenna housing 3 N 4w -Si powder;
and 8: vacuum carbonization: transferring the antenna housing obtained in the step 7 into a well type vacuum furnace, keeping the vacuum degree in the furnace below 0.01MPa, raising the temperature to 900 ℃ at the heating rate of 5 ℃/min, and preserving the temperature for 2 hours to convert acrylamide and methylene bisacrylamide into pyrolytic carbon;
and step 9: nitriding of Si powder: after the heat preservation in the step 8 is finished, introducing nitrogen into the well type vacuum furnace to normal pressure, wherein the flow rate of the nitrogen is 100mL/min, keeping the flow rate of the nitrogen unchanged, raising the temperature to 1390 ℃ at the heating rate of 5 ℃/min, raising the temperature to 1450 ℃ at the heating rate of 3 ℃/min, preserving the heat for 2h, enabling Si powder and the nitrogen to react, and generating Si in situ 3 N 4 。
This example increased the amount of binder added to mix the printing powder in step 4, printed Si, compared to example 1 3 N 4w The Si radome green body has higher strength than example 1, exhibits excellent formability and powder removal, and after the Si powder nitridation of step 9 is completed, the finally obtained Si radome green body has higher strength, and exhibits excellent formability and powder removal performance 3 N 4w /Si 3 N 4 The porosity of the composite material antenna housing is 50%, the composite material antenna housing has excellent wave-transmitting performance, and can be used for low-Mach aircraft.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. The scope of protection for the invention should be limited by the attached claims.
Comparative example
Step 1: preparation of Si 3 N 4 Whisker slurry: preparing a premixed solution by using 81% of deionized water, 10% of dextrin (binder), 1% of polyethylene glycol (plasticizer), 6% of tetramethylammonium hydroxide aqueous solution (the mass fraction is more than 25%, pH regulator) and 2% of ammonium polyacrylate aqueous solution (the mass fraction is more than 40%, dispersant) in terms of mass fraction for later use;
mixing 40% of premixed solution and 60% of Si in percentage by mass 3 N 4 Mixing the whisker powder to obtain Si 3 N 4 A whisker slurry;
in the aboveAdding ZrO into the slurry 2 Ball milling beads, wherein the mass ratio of the ball milling beads to the slurry is 3;
and 2, step: preparation of Si 3 N 4 Whisker microspheres: uniformly and stably adding Si obtained in the step 1 3 N 4 Granulating the whisker slurry in a spray dryer, wherein the air inlet temperature is 200 ℃, the air outlet temperature is 80 ℃, the slurry flow is 30mL/min, the rotation speed of an atomizing disc is 24000r/min, and collecting to obtain Si 3 N 4 Whisker microspheres;
and 3, step 3: mixing printing powder: with Si 3 N 4 Taking the mass of the whisker microsphere as a reference, adding acrylamide accounting for 10% of the mass of the whisker microsphere and methylene bisacrylamide accounting for 3.3% of the total mass of the whisker microsphere, and mechanically mixing the prepared powder in a horizontal ball mill for 2 hours;
and 4, step 4:3D printing antenna housing: and (4) filling the uniformly mixed powder obtained in the step (3) into a powder box of a powder printer, and starting to print the radome biscuit. Wherein the thickness of the powder layer is 0.1mm, and the saturation of the binder is 170%/340%;
and 5: heating, crosslinking and curing: the printed radome biscuit (containing excessive Si on the inner surface and the outer surface) 3 N 4 Whisker powder) is transferred into a forced air drying oven for crosslinking and curing, wherein the crosslinking temperature is 80 ℃, and the crosslinking time is 40min;
step 6: biscuit powder removal: removing excessive Si on the outer surface and the inner side of the completely solidified antenna housing 3 N 4 Whisker powder;
and 7: and (3) empty burning and degreasing: transferring the completely cured antenna housing into a box furnace, heating to 600 ℃ at the heating rate of 3 ℃/min, preserving heat for 4h, oxidizing and removing the crosslinked and cured acrylamide and methylene bisacrylamide to obtain porous Si 3 N 4 A whisker antenna housing.
In the comparative example, no pre-oxidized Si powder was added during spray drying and mixing of the printing powder, and after printing was completed, the binders acrylamide and methylene bisacrylamide were removed by a dry-fire degreasing method. Due to spray-dried Si 3 N 4 No Si powder generated by in-situ nitridation in crystal whisker microsphere and among microspheres 3 N 4 Finally obtained porous Si 3 N 4 The mechanical strength of the whisker radome is low, the whisker radome is very easy to collapse (damage) in the transfer process, and a nitride matrix cannot be further prepared.

Claims (9)

1. The utility model provides a silicon nitride whisker reinforcing nitride composite for 3D prints radar antenna house which characterized in that the component of mass fraction meter is: 9.1% -28.6% of surface modified Si powder and 71.4% -90.9% of Si 3 N 4w -Si composite microspheres of Si 3 N 4w Taking the total mass of the Si composite microspheres and the surface modified Si powder as a reference, and then adding 9.1-28.6% of acrylamide and 1.5-9.5% of methylenebisacrylamide; the surface modified Si powder is formed by a layer of SiO with uniform thickness on the surface of Si powder 2 A layer; said Si 3 N 4w the-Si composite microspheres are 26-68% of Si in mass fraction 3 N 4w Granulating a mixed solution of-Si powder and 32% -74% of premixed liquid to obtain Si 3 N 4w -Si composite microspheres; the premix comprises 80-90% of deionized water, 6-17% of dextrin, 0.2-2% of polyethylene glycol, 2-10% of tetramethylammonium hydroxide aqueous solution and 0.5-2% of ammonium polyacrylate aqueous solution in percentage by mass; said Si 3 N 4w -Si powder consisting of Si 3 N 4 The crystal whisker and the surface modified Si powder are composed of Si in mass fraction 3 N 4 The whisker accounts for 83.3% -90.9%, and the surface modified Si powder accounts for 9.1% -16.7%.
2. The silicon nitride whisker reinforced nitride composite material for a 3D printing radar radome of claim 1, wherein: siO on the surface of the surface-modified Si powder 2 The thickness of the layer is 20 to 100nm.
3. The silicon nitride whisker reinforced nitride composite material for a 3D printing radar radome of claim 1, wherein: said Si 3 N 4w The particle size distribution of the-Si composite microspheres is 10 to 100 mu m.
4. A method for preparing the silicon nitride whisker reinforced nitride composite material for the 3D printing radar antenna housing as defined in any one of claims 1 to 3, which is characterized by comprising the following steps:
step 1, surface modification of Si powder: carrying out heat treatment on Si powder with the particle size of 1-3 mu m for 1-10 h at the temperature of 700-1200 ℃ in an air atmosphere to form a layer of SiO with uniform thickness on the surface of the Si powder 2 Layer, obtaining surface modified Si powder;
step 2, preparing Si 3 N 4w -Si slurry: preparing 80-90% of deionized water, 6-17% of dextrin, 0.2-2% of polyethylene glycol, 2-10% of tetramethylammonium hydroxide aqueous solution and 0.5-2% of ammonium polyacrylate aqueous solution into a premixed solution by mass fraction;
according to the mass fraction, 32-74% of premixed liquid and 26-68% of Si are mixed 3 N 4w Mixing the-Si powder to obtain Si 3 N 4w -a Si slurry; said Si 3 N 4w -Si powder in mass fraction: from 83.3% to 90.9% of Si 3 N 4 The crystal whisker and 9.1% -16.7% of the surface modified Si powder obtained in the step (1);
in Si 3 N 4w ZrO addition to Si slurries 2 Ball milling bead, ball milling bead and Si 3 N 4w The mass ratio of Si slurry is (3) - (5) to 1, and the Si slurry is ball-milled and mixed in a horizontal ball mill, wherein the ball-milling rotating speed is 40 to 80r/min, and the ball-milling time is 8 to 36 hours;
step 3, preparation of Si 3 N 4w -Si composite microspheres: si obtained in the step 2 3 N 4w Putting the Si slurry into a spray dryer for granulation, wherein the air inlet temperature is 180-220 ℃, the air outlet temperature is 60-80 ℃, the slurry flow is 10-40 mL/min, the rotation speed of an atomizing disc is 6000-24000 r/min, and collecting to obtain the Si 3 N 4w -Si composite microspheres;
step 4, mixing and printing powder: according to the mass fraction, 71.4 to 90.9 percent of Si obtained in the step 3 3 N 4w And (3) mixing the-Si composite microspheres with 9.1-28.6% of the surface modified Si powder obtained in the step (1) to obtain silicon nitride whisker reinforced nitride composite material powder for the 3D printing radar antenna housing.
5. The method according to claim 4, characterized in that: the mass fraction of the tetramethylammonium hydroxide aqueous solution is more than 25%.
6. The method according to claim 4, characterized in that: the mass fraction of the ammonium polyacrylate aqueous solution is more than 40%.
7. A method for 3D printing of a radome with the silicon nitride whisker reinforced nitride composite material for the 3D printing of radomes according to any one of claims 1 to 3, which is characterized by comprising the following steps:
step 1): with Si 3 N 4w Taking the total mass of the Si composite microspheres and the surface modified Si powder as a reference, adding 9.1-28.6% of acrylamide and 1.5-9.5% of methylene bisacrylamide based on the total mass, and mechanically mixing the prepared powder in a horizontal ball mill for 1-4 hours to obtain uniformly mixed powder;
step 2), 3D printing the antenna housing: filling the uniformly mixed powder into a powder box of a powder printer, and starting to print an antenna housing biscuit; wherein the thickness of the powder spreading layer is 0.1mm, and the saturation degree of the binder is 100%/200% -170%/340%; the binder is ammonium persulfate aqueous solution;
step 3), heating, crosslinking and curing: transferring the printed antenna housing biscuit into a forced air drying oven for crosslinking and curing, wherein the crosslinking temperature is 60-100 ℃, and the crosslinking time is 20-120 min;
step 4), biscuit powder removal: removing excessive Si on the outer surface and the inner side of the completely solidified antenna housing 3 N 4w -Si composite microspheres to obtain a de-powderized radome biscuit;
step 5), vacuum carbonization: transferring the antenna housing biscuit obtained in the step 4) into a well type vacuum furnace, keeping the vacuum degree in the furnace below 0.01MPa, heating to 700-1000 ℃ at the heating rate of 3-10 ℃/min, and keeping the temperature for 1-3 h to convert acrylamide and methylene bisacrylamide into pyrolytic carbon;
step 6), si powderNitriding: after the heat preservation is finished, introducing nitrogen into the well type vacuum furnace to normal pressure, wherein the flow rate of the nitrogen is 20-200 mL/min, keeping the flow rate of the nitrogen unchanged, raising the temperature to 1300-1400 ℃ at the heating rate of 3-10 ℃/min, raising the temperature to 1400-1500 ℃ at the heating rate of 1-3 ℃/min, and preserving the heat for 1-3 h to enable the Si powder to react with the nitrogen, so as to generate Si in situ 3 N 4 Obtaining the antenna housing with the secondary pore characteristics; the secondary pores refer to Si 3 N 4 Submicron pores and Si between crystal grains in whisker microsphere 3 N 4 Micron-sized pores among the whisker microspheres.
8. The method of claim 7, wherein: after the radome with the secondary pore characteristics is completed in the step 6), a nitride matrix with a certain content is prepared in the radome with the secondary pore characteristics obtained in the step 6) by adopting a combined process of a Chemical Vapor Infiltration (CVI) method and a Precursor Impregnation Pyrolysis (PIP) method.
9. The method of claim 7, wherein: the mechanical mixing of step 1) is without ball milling.
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