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CN-121974699-A - Silicon carbide ceramic with interlocking microstructure formed by slender grains and preparation method thereof

CN121974699ACN 121974699 ACN121974699 ACN 121974699ACN-121974699-A

Abstract

The invention relates to an interlocking microstructure silicon carbide ceramic formed by slender grains and a preparation method thereof, belonging to the technical field of ceramic materials. The method takes alpha-SiC powder as a main raw material, and adds perhydro Polysilazane (PSZ) which is not subjected to crosslinking, curing or pretreatment in a certain proportion to prepare the ceramic composite powder. Subsequently, spark plasma sintering is performed under specific conditions to obtain a dense SiC ceramic having an interlocking microstructure formed of elongated grains. In the sintering process, trace nitrogen elements generated by the pyrolysis of the perhydro PSZ can regulate and control the stability of the alpha-SiC polytype, and induce the anisotropic growth of crystal grains along a specific crystal direction, so that an interlocking microstructure is formed. The structure can influence the fracture toughness of the material through crack deflection, bridging and other mechanisms, so as to realize the self-toughening of the ceramic material.

Inventors

  • ZHANG CHAOHUI
  • CHENG XINGWANG
  • ZHOU JINCHAO
  • JIA XIAOTONG
  • WANG QIANG
  • LI WENJUN

Assignees

  • 北京理工大学

Dates

Publication Date
20260505
Application Date
20260209

Claims (10)

  1. 1. A preparation method of interlocking microstructure silicon carbide ceramic formed by slender grains is characterized by comprising the following steps: The preparation of raw materials in the step (1), wherein the raw materials comprise alpha-SiC powder and perhydro PSZ, and the mass fraction of the perhydro PSZ is 7.5% -15% of the mass of the alpha-SiC powder; The step (2) of slurry preparation, which is to dissolve all-hydrogen PSZ in an organic solvent and stir to obtain transparent uniform PSZ solution, then add alpha-SiC powder, stir and mix uniformly to obtain mixed slurry; step (3) drying, namely evaporating and drying the slurry to obtain ceramic composite powder; And (4) spark plasma sintering, namely loading the ceramic composite powder into a graphite die, placing the graphite die into spark plasma sintering equipment, sintering, heating to 800-1000 ℃ when the initial vacuum degree is less than 10 Pa ℃ and preserving heat for 1-3 min, then starting to pressurize when the initial vacuum degree is increased to 1200+/-50 ℃, adding the pressure to 60-80 MPa when the initial vacuum degree is increased to 1600+/-50 ℃, finally keeping the pressure unchanged and increasing the temperature to 1700-1750 ℃ and preserving heat for 5-15 min, and cooling along with a furnace after sintering is finished to obtain the silicon carbide ceramic with the interlocking microstructure formed by the slender crystal grains.
  2. 2. The method of producing an interlocking microstructure silicon carbide ceramic having elongated crystal grains according to claim 1, wherein in the step (1), the particle size of the α -SiC powder is 40 to 50. Mu.m.
  3. 3. The method of claim 1, wherein in the step (1), the mass fraction of the perhydro PSZ is 7.5% -8.5% of the mass of the alpha-SiC powder.
  4. 4. The method of claim 1, wherein in the step (2), the organic solvent is butyl ether, and stirring is performed at a speed of 450-800 r/min for 30-60: 60 min, so as to obtain transparent and uniform PSZ solution.
  5. 5. The method of claim 1, wherein in the step (2), the mixed slurry is obtained by continuously stirring at 800-1000 r/min and 2-4 h after adding the alpha-SiC powder.
  6. 6. The method of claim 1, wherein in step (3), the mixed slurry is dried by heating in an oil bath under a negative pressure condition at a temperature of 110-120 ℃ and a flask rotation speed of 30-40 r/min for a drying time of 1-2 h to obtain a dried ceramic composite powder.
  7. 7. The method of producing an interlocking microstructure silicon carbide ceramic formed of elongated grains according to claim 1, wherein in the step (4), when the initial vacuum degree is less than 10 Pa, heating to 800-1000 ℃ at a heating rate of 40-60 ℃ per minute for 1-3 minutes, then heating to 1200+ -50 ℃ at a heating rate of 50-100 ℃ per minute, starting pressurizing, heating to 1600+ -50 ℃ at a heating rate of 50-100 ℃ per minute, adding a pressure to 60-80 MPa, finally keeping the pressure unchanged, continuing heating to 1700-1750 ℃ at a heating rate of 30-40 ℃ per minute for 5-10 min, and cooling with a furnace after sintering is completed, thereby obtaining the interlocking microstructure silicon carbide ceramic formed of elongated grains.
  8. 8. An interlocking microstructure silicon carbide ceramic formed by slender grains is characterized by being prepared by the method of any one of claims 1-7.
  9. 9. An interlocking microstructure silicon carbide ceramic formed of elongated grains according to claim 8 wherein the silicon carbide grains in the interlocking microstructure are elongated in morphology and have an average grain length to diameter ratio greater than 2.
  10. 10. The interlocking microstructure silicon carbide ceramic formed by the elongated grains according to claim 8, wherein the density of the interlocking microstructure silicon carbide ceramic formed by the elongated grains is more than or equal to 99%, the hardness is 25-30 GPa, and the fracture toughness is 5.5-8 MPa m 1/2 .

Description

Silicon carbide ceramic with interlocking microstructure formed by slender grains and preparation method thereof Technical Field The invention relates to an interlocking microstructure silicon carbide ceramic formed by slender grains and a preparation method thereof, belonging to the technical field of ceramic materials. Background Silicon Carbide (SiC) ceramics have been widely used in the fields of aerospace, national defense equipment, nuclear engineering, semiconductor manufacturing, and the like, because of their high melting point, high hardness, low density, excellent thermal stability and oxidation resistance. However, conventional SiC ceramics have low fracture toughness and insufficient damage tolerance, and their intrinsic brittleness has become an important factor limiting their further application in severe service environments. In order to improve the fracture toughness of SiC ceramics, the prior art mainly adopts modes of fiber reinforcement or introducing second phase toughening and the like. Although the fiber reinforcement can obviously improve the toughness, the preparation process is complex, the cost is high, the anisotropy of mechanical properties is obvious, and the like, and the introduction of a second phase such as metal or low-melting-point oxide and the like often reduces the high-temperature performance, the hardness and the corrosion resistance of the material, so that the intrinsic advantage of the SiC ceramic is weakened. On the premise of not introducing external reinforcing phases, the self-toughening is realized by regulating the morphology of the crystal grains, and the method is considered as an ideal technical approach. The inventor researches find that when SiC grains are changed from equiaxed morphology into long and thin grains with high length-diameter ratio, and mutually staggered interlocking structures are formed on a microscopic scale, fracture toughness can be effectively improved through mechanisms such as crack deflection, crack bridging, grain interlocking and the like. However, since SiC is a strongly covalent bond material, the atomic diffusivity is limited, and its grain anisotropic growth typically depends on long-time high temperature treatment (> 1950 ℃) or the introduction of sintering aids, it is difficult to directly obtain elongated grains and interlocking structures at lower temperatures without sintering aids. Therefore, it is needed to provide a new preparation method of SiC ceramics, which realizes the construction of the elongated crystal grains and the interlocking microstructure by direct sintering under the conditions of no need of introducing external reinforcing phase and no need of complex pretreatment process, thereby improving the comprehensive mechanical properties of the material while ensuring the purity of the material. Disclosure of Invention In view of the above, the present invention aims to provide an interlocking microstructure silicon carbide ceramic formed by elongated grains and a preparation method thereof. The method takes alpha-SiC powder as a main raw material, and adds perhydro Polysilazane (PSZ) which is not subjected to crosslinking, curing or pretreatment in a certain proportion to prepare the ceramic composite powder. Subsequently, spark plasma sintering is performed under specific conditions to obtain a dense SiC ceramic having an interlocking microstructure formed of elongated grains. In the sintering process, trace nitrogen elements generated by the pyrolysis of the perhydro PSZ can regulate and control the stability of the alpha-SiC polytype, and induce the anisotropic growth of crystal grains along a specific crystal direction, so that an interlocking microstructure is formed. The structure can influence the fracture toughness of the material through crack deflection, bridging and other mechanisms, so as to realize the self-toughening of the ceramic material. In order to achieve the above object, the technical scheme of the present invention is as follows. A method for preparing silicon carbide ceramic with an interlocking microstructure formed by slender grains, comprising the following steps: the preparation of raw materials in the step (1) comprises the steps of preparing raw materials of alpha-SiC powder and perhydro Polysilazane (PSZ), wherein the mass fraction of the perhydro PSZ is 7.5% -15% of the mass of the alpha-SiC powder; The step (2) of slurry preparation, which is to dissolve all-hydrogen PSZ in an organic solvent and stir to obtain transparent uniform PSZ solution, then add alpha-SiC powder, stir and mix uniformly to obtain mixed slurry; step (3) drying, namely evaporating and drying the slurry to obtain ceramic composite powder; And (4) spark plasma sintering, namely loading the ceramic composite powder into a graphite die, placing the graphite die into spark plasma sintering equipment, sintering, heating to 800-1000 ℃ when the initial vacuum degree is less than 10 Pa ℃ and preserving heat for