CN115295198B - Method for preparing full ceramic micro-package dispersion fuel by oscillation sintering - Google Patents
Method for preparing full ceramic micro-package dispersion fuel by oscillation sintering Download PDFInfo
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- CN115295198B CN115295198B CN202210932513.0A CN202210932513A CN115295198B CN 115295198 B CN115295198 B CN 115295198B CN 202210932513 A CN202210932513 A CN 202210932513A CN 115295198 B CN115295198 B CN 115295198B
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- 238000005245 sintering Methods 0.000 title claims abstract description 108
- 230000010355 oscillation Effects 0.000 title claims abstract description 100
- 239000000446 fuel Substances 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 36
- 239000000919 ceramic Substances 0.000 title claims abstract description 34
- 239000006185 dispersion Substances 0.000 title claims abstract description 24
- 239000004005 microsphere Substances 0.000 claims abstract description 55
- 239000000843 powder Substances 0.000 claims abstract description 53
- 230000000630 rising effect Effects 0.000 claims abstract description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 27
- 239000010439 graphite Substances 0.000 claims abstract description 27
- 238000004321 preservation Methods 0.000 claims abstract description 25
- 229910052582 BN Inorganic materials 0.000 claims abstract description 16
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000011049 filling Methods 0.000 claims abstract description 13
- 238000005538 encapsulation Methods 0.000 claims abstract description 12
- 230000008569 process Effects 0.000 claims abstract description 9
- 239000002245 particle Substances 0.000 claims description 11
- 239000011248 coating agent Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 claims 1
- 238000000280 densification Methods 0.000 abstract description 20
- 239000011159 matrix material Substances 0.000 abstract description 11
- 230000000052 comparative effect Effects 0.000 description 13
- 238000005303 weighing Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 8
- 239000010410 layer Substances 0.000 description 7
- 230000003068 static effect Effects 0.000 description 6
- 239000008188 pellet Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 4
- 229910010293 ceramic material Inorganic materials 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000007731 hot pressing Methods 0.000 description 3
- 239000002131 composite material Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000005324 grain boundary diffusion Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000008707 rearrangement Effects 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000004992 fission Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
- G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
- G21C21/16—Manufacture of fuel elements or breeder elements contained in non-active casings by casting or dipping techniques
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
- G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
- G21C21/04—Manufacture of fuel elements or breeder elements contained in non-active casings by vibrational compaction or tamping of fuel in the jacket
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention discloses a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering, which comprises the following steps: s1, filling a plurality of layers of coated fuel microspheres and SiC powder into a graphite mold sprayed with boron nitride; s2, placing the graphite die into an oscillation sintering furnace for oscillation sintering: the temperature control process comprises the following steps: the temperature rising rate of the room temperature to 1200 ℃ is 5 to 15 ℃/min, the temperature rising rate of the 1200 ℃ to the target temperature is 3 to 5 ℃/min, the temperature is preserved at the target temperature, and the furnace is cooled after the heat preservation is finished; the pressure control is as follows: before the temperature is raised to the target temperature, the pressure is kept at 1-5 MPa, after the target temperature is reached, the target oscillation pressure is applied, and after the heat preservation is finished, the pressure is relieved. The invention not only can realize the sintering densification of the SiC matrix, but also has lower sintering temperature and higher densification rate compared with hot-press sintering.
Description
Technical Field
The invention relates to the technical field of ceramic material preparation, in particular to a method for preparing full-ceramic micro-encapsulation dispersion fuel by oscillation sintering.
Background
The full ceramic micro-encapsulated dispersion fuel is a fuel with a plurality of layers of encapsulated fuel microspheres dispersed on a SiC ceramic matrix, has excellent performances of high heat conduction, high irradiation stability, excellent fission product containing capacity and the like, has good compatibility with a coolant, is suitable for a high-burnup reactor, and has higher accident fault tolerance and safety guarantee.
The organization structure of the SiC matrix has important influence on the performance of the all-ceramic micro-encapsulated dispersion fuel, but the SiC ceramic has the problems of small sintering driving force, low volume diffusion rate, low grain boundary diffusion rate and the like in the sintering process, so that the SiC matrix is difficult to sinter and densify. In order to prepare the compact high-strength full ceramic micro-encapsulated fuel pellets, a pressure-assisted sintering method is generally adopted. However, conventional hot-pressed sintering cannot fully realize particle rearrangement, particle aggregates cannot be fully eliminated, residual air holes at grain boundaries cannot be effectively removed, and the structure of the multilayer coated microsphere is damaged due to excessive pressure.
Disclosure of Invention
The invention aims to provide a method for preparing full ceramic micro-package dispersion fuel by oscillation sintering, which not only can realize SiC matrix sintering densification, but also has lower sintering temperature and higher densification rate compared with hot-press sintering.
The invention is realized by the following technical scheme:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, filling a plurality of layers of coated fuel microspheres and SiC powder into a graphite mold sprayed with boron nitride;
s2, placing the graphite die into an oscillation sintering furnace for oscillation sintering:
the temperature control process comprises the following steps: the temperature rising rate of the room temperature to 1200 ℃ is 5 to 15 ℃/min, the temperature rising rate of the 1200 ℃ to the target temperature is 3 to 5 ℃/min, the temperature is preserved at the target temperature, and the furnace is cooled after the heat preservation is finished;
the pressure control is as follows: before the temperature is raised to the target temperature, the pressure is kept at 1-5 MPa, after the target temperature is reached, the target oscillation pressure is applied, and after the heat preservation is finished, the pressure is relieved.
The oscillating sintering is a sintering method for promoting powder densification and improving material strength by utilizing dynamic pressure in the sintering process, can effectively promote rearrangement of powder particles under relatively small pressure, can provide enough driving force for plastic flow of grain boundaries, promote plastic sliding among grains, enable soft agglomeration to be broken, further eliminate air holes, and has application in the aspect of full Tao Zhimi sintering, but the oscillating sintering is used for densification sintering of full ceramic micro-encapsulation dispersion fuel for the first time, and for densification sintering of different ceramic materials by using oscillating sintering, the key difference point and improvement point are temperature control and pressure control in the oscillating sintering process, and reasonable temperature control parameters and pressure control parameters are required to be designed for different ceramic materials, so that densification of the sintered materials is realized.
According to the characteristics of the multilayer coated fuel microspheres and the SiC powder and the specific application environment of the prepared full-ceramic micro-encapsulated dispersion fuel, the temperature control and the pressure control in the oscillation sintering process are reasonably designed, so that the sintering densification of the SiC matrix is realized, and compared with the hot-press sintering, the sintering densification of the SiC matrix is realized, and the sintering temperature is lower and the densification rate is higher.
Further, in step S1, the average particle diameter of the multilayer coated fuel microspheres is 500 to 1100 μm, and the average particle diameter of the SiC powder is 0.01 to 10. Mu.m.
The average grain diameter of the fuel microsphere is 500-1100 mu m, which not only ensures that the outer layer effectively coats the fuel microsphere, but also ensures that the fuel microsphere has good fluidity and can be effectively dispersed in the matrix. If the particle size of the SiC powder is too small, the oxygen content is too high, and the powder purity is insufficient; if the particle size of the SiC powder is too large, the particle gap is too large, and the bulk density is small, which is unfavorable for densification.
Further, in step S1, the volume percentage of the multi-layer coated fuel microsphere is 10-55%, and the volume percentage of the SiC powder is 45-90%.
The volume fraction can ensure that the fuel microspheres are uniformly dispersed in the SiC matrix without contact.
Further, in step S1, the average thickness of the boron nitride coating layer is 30 to 100 μm.
The main purpose of spraying boron nitride with a certain thickness is to prevent the sample from adhering to or reacting with the graphite mold, so that the demolding is convenient.
Further, in step S2, the target temperature is 1600 to 1850 ℃.
Further, in the step S2, the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, and the temperature rising rate of the 1200 ℃ to the target temperature is 3 ℃/min.
Further, in the step S2, the heat preservation time is 1-5 h.
Further, in step S2, the oscillation time is 0 to 2 hours.
Further, in step S2, the median pressure value of the target oscillation pressure is 10-20 MPa, the pressure amplitude is 1-5 MPa, and the oscillation frequency is 1-5 Hz.
If the median value of the pressure is too small, the density of the sample is low; when the median pressure is too high, the fuel microspheres are easily deformed and broken. The reason for the pressure amplitude is similar to the median pressure. The oscillating pressure has a frequency range of effects, and too high or too low a frequency is detrimental to densification.
Further, in step S2, the oscillation form of the target oscillation pressure is sinusoidal oscillation.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the invention provides a method for preparing a full-ceramic micro-encapsulated fuel pellet by oscillation sintering, which effectively reduces the sintering temperature of a ceramic matrix, shortens the sintering time, improves the densification rate and density, optimizes the microstructure, and can solve the problem that the SiC matrix of the full-ceramic micro-encapsulated fuel pellet is difficult to sinter and densify due to small sintering driving force, low volume diffusion rate, low grain boundary diffusion rate and the like caused by hot-pressed sintering.
2. The raw materials of the invention are a powdery material and another microsphere-shaped different material, and the high-density full-ceramic composite core block is prepared by adopting the method of the invention, and the operation is convenient, and the equipment can be reused, so that the invention can be widely applied to the preparation of ceramic composite materials.
Drawings
The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention. In the drawings:
FIG. 1 is a graph of sintering curves for example 1 oscillation sintering (1750-20.+ -. 5MPa-2 h) to produce fully ceramic microencapsulated fuel pellets in comparison to hot press sintering (1750-20 MPa-2h, 1800-20 MPa-2 h). Wherein, (a) is the sintering curve of the oscillation sintering (1750-20+/-5 MPa-2 h) and the sintering curve of the hot pressing sintering (1750-20 MPa-2h, 1800-20 MPa-2 h) are compared; (b) The densification rate of the oscillating sintering sample at 1750 ℃ is compared with the densification rate of the hot pressing sintering sample at 1750 ℃;
FIG. 2 is the hardness of the oscillation sintering (1800-20.+ -. 5MPa-2 h) of example 2 to prepare and hot press sintering of the full ceramic micro-encapsulated fuel pellets (1800-20 MPa-2 h);
FIG. 3 is a graph showing the distribution of SEM and grain size of the cross section of the samples of example 3, vibration sintering (1850-20+ -5 MPa-2 h) and hot press sintering (1850-20 MPa-2 h): oscillating sintering (a) and (c); and (b) and (d) hot pressing sintering.
FIG. 4 shows densities of the oscillation sintered samples of examples 1 (1750 ℃ C. To 20.+ -. 5MPa-2 h), 4 (1750 ℃ C. To 15.+ -. 5MPa-2 h) and 5 (1750 ℃ C. To 8.+ -. 5MPa-2 h).
FIG. 5 shows densities of sintered samples of example 1 (1750 ℃ C. To 20.+ -. 5MPa-2 h) and comparative examples 4 (1750 ℃ C. To 20.+ -. 5MPa-1 h) and 5 (1750 ℃ C. To 20MPa-0 h).
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for illustrating the present invention only and are not to be construed as limiting the present invention.
Example 1:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1750 ℃ is 3 ℃/min, the heat is preserved for 2 hours at 1750 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1750 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1750 ℃, the target oscillation pressure of 20+/-5 MPa is applied, the oscillation time is 2 hours, and after the heat preservation is finished, the pressure is relieved.
In this embodiment, the oscillation form is sinusoidal oscillation, and the pressure median value of the target oscillation pressure is 20MPa, the pressure amplitude is 5MPa, and the oscillation frequency is 2Hz.
Comparative example 1:
the hot pressed sintered sample at 1750 ℃ is prepared, and the specific process is as follows:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multi-layer coated fuel microspheres and the SiC powder into a hot-press sintering furnace for hot-press sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1750 ℃ is 3 ℃/min, the heat is preserved for 2 hours at 1750 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1750 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1750 ℃, the target static pressure of 20MPa is applied, the static pressure time is 2h, and after the heat preservation is finished, the pressure is relieved.
Comparative example 2:
the preparation method of the hot pressed sintering sample at 1800 ℃ comprises the following specific processes:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multi-layer coated fuel microspheres and the SiC powder into a hot-press sintering furnace for hot-press sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1800 ℃ is 3 ℃/min, the heat is preserved for 2 hours at 1800 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1800 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1800 ℃, the target static pressure of 20MPa is applied, the static pressure time is 2h, and after the heat preservation is finished, the pressure is relieved.
The sintering curves of example 1, comparative example 1 and comparative example 2 are shown in fig. 1 (a): the density of the vibration sintering sample at 1750 ℃ is obviously higher than that of the hot press sintering sample at 1750 ℃, which shows that the vibration sintering obviously improves the density of the material; the density of the vibration sintering sample at 1750 ℃ is almost consistent with that of the hot press sintering sample at 1800 ℃, which shows that the vibration sintering is helpful for reducing the sintering temperature.
The densification rates of example 1 and comparative example 1 are shown in fig. 1 (b): the densification rate of the green sintered samples at 1750 ℃ was significantly higher than the densification rate of the hot pressed sintered samples at 1750 ℃, indicating that green sintering helps to increase the densification rate of the samples.
Example 2:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1800 ℃ is 3 ℃/min, the heat is preserved for 2 hours at 1800 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1800 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1800 ℃, the target oscillation pressure of 20+/-5 MPa is applied, the oscillation time is 2 hours, and after the heat preservation is finished, the pressure is relieved.
In this embodiment, the oscillation form is sinusoidal oscillation, and the pressure median value of the target oscillation pressure is 20MPa, the pressure amplitude is 5MPa, and the oscillation frequency is 2Hz.
The hardness of the samples prepared in example 2 and comparative example 2 was measured, and the results are shown in fig. 2: the hardness (26.7+/-0.4 GPa) of the vibration sintering sample is obviously larger than that (25.9+/-0.7 GPa) of the hot-press sintering sample, and the vibration pressure effectively improves the mechanical property of the material. In addition, the hardness deviation of the vibration sintering sample is obviously smaller than that of the hot press sintering sample, which proves that the vibration sintering is helpful for preparing the material with more uniform microstructure and more stable material performance
Example 3:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1850 ℃ is 3 ℃/min, the temperature is kept for 2 hours at 1850 ℃, and the furnace is cooled after the temperature is kept;
setting a pressure control program: maintaining the pressure of 3MPa before the temperature is increased to 1850 ℃, applying the target oscillation pressure of 20+/-5 MPa after the temperature reaches 1850 ℃, oscillating for 2 hours, and releasing pressure after the heat preservation is finished.
In this embodiment, the oscillation form is sinusoidal oscillation, and the pressure median value of the target oscillation pressure is 20MPa, the pressure amplitude is 5MPa, and the oscillation frequency is 2Hz.
Comparative example 3:
the preparation of 1850 ℃ hot pressed sintered sample comprises the following specific procedures:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multi-layer coated fuel microspheres and the SiC powder into a hot-press sintering furnace for hot-press sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1850 ℃ is 3 ℃/min, the temperature is kept for 2 hours at 1850 ℃, and the furnace is cooled after the temperature is kept;
setting a pressure control program: maintaining the pressure of 3MPa before the temperature is raised to 1850 ℃, applying the target static pressure of 20MPa after the temperature reaches 1850 ℃, and releasing pressure after the temperature is kept for 2 hours.
The crystal grain sizes of the sample prepared in example 3 and the hot pressed sintered sample prepared in comparative example 3 were observed by SEM scanning, and the results are shown in fig. 3:
the crystal grain sizes of the sample prepared in example 3 and the hot pressed sintered sample prepared in comparative example 3 were observed by SEM scanning, and the results are shown in fig. 3:
as can be seen from fig. 3, the grain size (284.1±3.9 nm) of the oscillation sintered sample is significantly smaller than the grain size (396.3 ±6.8 nm) of the hot press sintered sample, and the oscillation pressure is effective to suppress the grain growth. In addition, from the statistical grain size distribution, the particle size distribution of the oscillation sintered sample is narrower and the microstructure is more uniform.
Example 4:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1750 ℃ is 3 ℃/min, the heat is preserved for 2 hours at 1750 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1750 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1750 ℃, the target oscillation pressure of 15+/-5 MPa is applied, the oscillation time is 2 hours, and after the heat preservation is finished, the pressure is relieved.
In this embodiment, the oscillation form is sinusoidal oscillation, the pressure median value of the target oscillation pressure is 15MPa, the pressure amplitude is 5MPa, and the oscillation frequency is 2Hz.
Example 5:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1750 ℃ is 3 ℃/min, the heat is preserved for 2 hours at 1750 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1750 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1750 ℃, the target oscillation pressure of 10+/-5 MPa is applied, the oscillation time is 2 hours, and after the heat preservation is finished, the pressure is relieved.
In this embodiment, the oscillation form is sinusoidal oscillation, the pressure median value of the target oscillation pressure is 8MPa, the pressure amplitude is 5MPa, and the oscillation frequency is 2Hz.
The density of the samples prepared in examples 1, 4 and 5 was measured by the archimedes' drainage method, and the results are shown in fig. 4:
as can be seen from fig. 4, when the median pressure of the oscillation sintering is lower than 10MPa, the density of the sample is lower, the relative density is only about 80%, and the sample is obviously not dense; and when the pressure is higher than 10MPa, the compactness of the sample is obviously improved, and the relative density is higher than 95%. That is, the vibration sintering requires a proper median pressure, the pressure is too small, the sample density is low, and the requirement is difficult to meet; too high pressure, too high equipment and die requirements, and significant increases in cost.
Comparative example 4:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1750 ℃ is 3 ℃/min, the heat is preserved for 1h at 1750 ℃, and the furnace is cooled after the heat preservation is finished;
setting a pressure control program: before the temperature is raised to 1750 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1750 ℃, the target oscillation pressure of 20+/-5 MPa is applied, the oscillation time is 1h, and after the heat preservation is finished, the pressure is relieved.
In this embodiment, the oscillation form is sinusoidal oscillation, and the pressure median value of the target oscillation pressure is 20MPa, the pressure amplitude is 5MPa, and the oscillation frequency is 2Hz.
Comparative example 5:
a method for preparing full ceramic micro-encapsulation dispersion fuel by oscillation sintering comprises the following steps:
s1, weighing 16g of multilayer coated fuel microspheres and SiC powder, and filling into a phi 30mm graphite die sprayed with boron nitride;
the average grain diameter of the multilayer coated fuel microsphere is 1000 mu m, the average grain diameter of the SiC powder is 40nm, the volume percentage of the multilayer coated fuel microsphere is 22%, and the volume percentage of the SiC powder is 78%.
S2, placing a graphite die filled with the multilayer coated fuel microspheres and the SiC powder into an oscillation sintering furnace for oscillation sintering:
setting a temperature control program: the temperature rising rate of the room temperature to 1200 ℃ is 10 ℃/min, the temperature rising rate of the 1200 ℃ to 1750 ℃ is 3 ℃/min, the temperature is not preserved for 0h at 1750 ℃, and the furnace is directly cooled;
setting a pressure control program: before the temperature is raised to 1750 ℃, the pressure of 3MPa is maintained, after the temperature reaches 1750 ℃, the target static pressure of 20MPa is applied, and then the pressure is relieved.
The density of the samples prepared in example 1 and comparative examples 4 and 5 was measured by archimedes' drainage method, and the results are shown in fig. 5:
as can be seen from fig. 5, when the holding time of the oscillation sintering is less than 1h, the density of the sample is lower, the relative density is less than 90%, and the sample is obviously not dense; and when the heat preservation time is 2 hours, the density of the sample is obviously improved, and the relative density reaches about 98 percent. That is, the oscillation sintering requires a proper heat preservation time, the time is too short, the sample density is low, and the requirement is difficult to meet; the time is too long, the grains are easy to grow up, and the equipment and die cost is obviously increased.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. The method for preparing the all-ceramic micro-encapsulated dispersion fuel by oscillation sintering is characterized by comprising the following steps of:
s1, filling a plurality of layers of coated fuel microspheres and SiC powder into a graphite mold sprayed with boron nitride;
s2, placing the graphite die into an oscillation sintering furnace for oscillation sintering:
the temperature control process comprises the following steps: the temperature rising rate of the room temperature to 1200 ℃ is 5-15 ℃/min, the temperature rising rate of the 1200 ℃ to the target temperature is 3-5 ℃/min, the heat is preserved at the target temperature, and the furnace is cooled after the heat preservation is finished;
the pressure control is as follows: maintaining the pressure of 1-5 MPa before the temperature is raised to the target temperature, applying the target oscillating pressure after the target temperature is reached, and releasing pressure after the heat preservation is finished;
in the step S2, the target temperature is 1600-1850 ℃; in the step S2, the heat preservation time is 2-5 h; in the step S2, the pressure median value of the target oscillation pressure is 10-20 MPa, the pressure amplitude is 1-5 MPa, and the oscillation frequency is 1-5 Hz.
2. The method for preparing the all-ceramic micro-encapsulated dispersion fuel by oscillation sintering according to claim 1, wherein in the step S1, the average particle size of the multi-layer encapsulated fuel microspheres is 500-1100 μm, and the average particle size of the SiC powder is 0.1-10 μm.
3. The method for preparing the all-ceramic micro-encapsulated dispersion fuel by oscillation sintering according to claim 1, wherein in the step S1, the volume percentage of the multi-layer coated fuel microspheres is 10-55%, and the volume percentage of the SiC powder is 45-90%.
4. The method for preparing the all-ceramic micro-encapsulated dispersion fuel by oscillation sintering according to claim 1, wherein in the step S1, the average thickness of the boron nitride coating is 30-100 μm.
5. The method for preparing the all-ceramic micro-encapsulated dispersion fuel by oscillation sintering according to claim 1, wherein in the step S2, the temperature rising rate of room temperature to 1200 ℃ is 10 ℃/min, and the temperature rising rate of 1200 ℃ to target temperature is 3 ℃/min.
6. The method for preparing the all-ceramic micro-package dispersion fuel by oscillation sintering according to claim 1, wherein in the step S2, the oscillation time is 0-2 h.
7. The method for preparing a dispersion fuel in a micro-encapsulation of all ceramics according to any one of claims 1 to 6, wherein in step S2, the oscillation form of the target oscillation pressure is sinusoidal oscillation.
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