CN116768648B - Three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, preparation method and application - Google Patents
Three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, preparation method and application Download PDFInfo
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- 239000002243 precursor Substances 0.000 title claims abstract description 84
- 239000002086 nanomaterial Substances 0.000 title claims abstract description 50
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 46
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 46
- 239000010703 silicon Substances 0.000 title claims abstract description 46
- 239000000919 ceramic Substances 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 83
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 68
- 239000010439 graphite Substances 0.000 claims abstract description 68
- 238000007710 freezing Methods 0.000 claims abstract description 59
- 230000008014 freezing Effects 0.000 claims abstract description 59
- 239000007788 liquid Substances 0.000 claims abstract description 58
- 239000002121 nanofiber Substances 0.000 claims abstract description 55
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 45
- 239000004964 aerogel Substances 0.000 claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 32
- 239000008367 deionised water Substances 0.000 claims abstract description 29
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 29
- 229910010293 ceramic material Inorganic materials 0.000 claims abstract description 28
- 239000006185 dispersion Substances 0.000 claims abstract description 25
- 238000002156 mixing Methods 0.000 claims abstract description 22
- 238000004108 freeze drying Methods 0.000 claims abstract description 19
- 238000001035 drying Methods 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 16
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 9
- 238000005272 metallurgy Methods 0.000 claims abstract description 6
- 238000010248 power generation Methods 0.000 claims abstract description 6
- 238000000465 moulding Methods 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 83
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 68
- 229910052757 nitrogen Inorganic materials 0.000 claims description 34
- 238000010438 heat treatment Methods 0.000 claims description 28
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 21
- 229910052802 copper Inorganic materials 0.000 claims description 17
- 239000010949 copper Substances 0.000 claims description 17
- 238000003756 stirring Methods 0.000 claims description 15
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 14
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 13
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 claims description 12
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 12
- 229910021389 graphene Inorganic materials 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 6
- 238000007667 floating Methods 0.000 claims description 6
- -1 polytetrafluoroethylene Polymers 0.000 claims description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- 239000011889 copper foil Substances 0.000 claims description 4
- 239000013078 crystal Substances 0.000 claims description 4
- 238000000502 dialysis Methods 0.000 claims description 4
- 239000005457 ice water Substances 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 230000007935 neutral effect Effects 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 abstract description 9
- 230000003647 oxidation Effects 0.000 abstract description 4
- 238000007254 oxidation reaction Methods 0.000 abstract description 4
- 238000003763 carbonization Methods 0.000 abstract description 2
- 238000005336 cracking Methods 0.000 abstract description 2
- 239000000945 filler Substances 0.000 abstract description 2
- 238000000197 pyrolysis Methods 0.000 abstract description 2
- 238000005245 sintering Methods 0.000 abstract description 2
- 239000000499 gel Substances 0.000 description 43
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 22
- 229910052786 argon Inorganic materials 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
- 239000002250 absorbent Substances 0.000 description 8
- 230000002745 absorbent Effects 0.000 description 8
- 230000006835 compression Effects 0.000 description 7
- 238000007906 compression Methods 0.000 description 7
- 239000002131 composite material Substances 0.000 description 6
- 239000000835 fiber Substances 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 239000004966 Carbon aerogel Substances 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 239000002893 slag Substances 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 210000002345 respiratory system Anatomy 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- 229920002522 Wood fibre Polymers 0.000 description 1
- CFOAUMXQOCBWNJ-UHFFFAOYSA-N [B].[Si] Chemical compound [B].[Si] CFOAUMXQOCBWNJ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
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- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- YOBAEOGBNPPUQV-UHFFFAOYSA-N iron;trihydrate Chemical compound O.O.O.[Fe].[Fe] YOBAEOGBNPPUQV-UHFFFAOYSA-N 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012286 potassium permanganate Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 239000002025 wood fiber Substances 0.000 description 1
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Abstract
The invention belongs to the technical field of materials, and discloses a preparation method of a three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, which comprises the following steps: mixing the nanofiber gel with deionized water, and performing ultrasonic treatment; mixing the dispersion liquid and the graphite oxide solution, placing the mixture in a directional freezing mold, and taking out the mixture for freeze drying after molding; immersing in SiBCN precursor solution in vacuum, taking out, drying, and maintaining the temperature. According to the method, the nano fiber/graphite oxide aerogel is taken as a framework, the SiBCN precursor is taken as a filler, pyrolysis carbonization and the cracking and sintering of the SiBCN precursor are simultaneously carried out, and the three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic material is obtained, has excellent high temperature resistance and oxidation resistance, has excellent mechanical properties, and has wide application prospect in the fields of aerospace, chemical metallurgy, nuclear power generation and the like.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, a preparation method and application.
Background
Silicon boron carbonitride (SiBCN) ceramics have remarkable ultra-high temperature stability, excellent oxidation resistance and creep resistance, which makes them potentially useful in the field of high temperature structural ceramics. The strengthening and toughening are always directions required to be explored in the research of ceramic materials, and the ceramic fiber has the advantages of high temperature resistance, oxidation resistance, good chemical stability, good mechanical vibration resistance and the like, and can be used as a reinforcement of aerogel materials and can be independently used as a high-temperature heat insulation material, so that the ceramic fiber has wide application prospects in the fields of aerospace, chemical metallurgy, nuclear power generation and the like.
However, the existing ceramic composite aerogel has the following disadvantages: during compression, dust and slag are heavier, and the dust and slag are harmful to respiratory systems of constructors, so that environmental pollution is easy to cause; because of the addition of the binder, the high temperature limit of the aerogel cannot exceed 800 ℃ generally, so that the application range of the aerogel is greatly limited; in a high compressive strain state, the composite material does not have good strength, cannot maintain superelasticity, and has mechanical properties such as high bearing capacity.
Therefore, how to solve the problems under the condition of larger deformation of the ceramic composite aerogel has important significance in practical application.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, a preparation method and application.
The technical scheme adopted for solving the technical problems is as follows:
a preparation method of a three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic comprises the following steps:
(1) Mixing nanofiber gel with deionized water, and performing ultrasonic treatment to obtain a dispersion liquid with the mass concentration of 0.3-1.0 wt%;
(2) Mixing the dispersion liquid with graphite oxide solution with the mass concentration of 0.3-1.0 wt%, preparing mixed gel by using a freeze-drying method, a hydrothermal method or an ethylenediamine method in the hydrothermal process, placing the mixed gel in a directional freezing mold, and taking out the mixed gel after molding and freeze-drying for 12-14 hours to obtain nanofiber/graphite oxide aerogel;
wherein the mass ratio of the nanofiber gel in the dispersion liquid to the graphene oxide in the graphene oxide aqueous solution is 3-8: 3 to 8;
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 60-80 min in a vacuum environment, taking out the nanofiber/graphite oxide aerogel, drying, and then preserving heat for 4-5 h at 250-350 ℃ in an inert gas environment and then preserving heat for 2-3 h at 950-1050 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material;
wherein the SiBCN precursor solution is a mixture of polyborosilazane and N-hexane, and the volume ratio of polyborosilazane to SiBC N precursor solution is 1:20.
further, the ultrasonic time in the step (1) is 60-70 s, and the ultrasonic power is 1200-1400W.
Further, the freeze-drying method in the step (2) is as follows: ultrasonic treatment is carried out for 30-40 min to gel state with power of 1100-1300W, water bath heating is carried out for 50-70 min at the temperature of 90-95 ℃, and cooling is carried out to room temperature, thus obtaining mixed gel;
alternatively, the hydrothermal method in the step (2) is as follows: ultrasonically crushing for 30-40 min at 150-160W power, reacting for 5-7 h at 120-130 ℃, dialyzing in an ethanol water solution with the mass concentration of 20wt% until floating in the ethanol water solution, and taking out to obtain a mixed gel;
or, the method of adding ethylenediamine in the hydrothermal process in the step (2) is as follows: crushing for 30-40 min with 150-160W power, adding ethylenediamine to regulate pH to 9.8-10.2 while stirring, reacting at 110-130 deg.c for 5-7 hr, dialyzing in 20wt% concentration alcohol solution until floating in the alcohol solution, and taking out to obtain mixed gel.
Further, the preparation method of the graphite oxide in the graphite oxide solution in the step (2) comprises the following steps:
graphite powder and NaNO 3 Mixing, placing in ice-water bath, adding H 2 SO 4 Adding KMnO within 40min 4 Continuously stirring during the process, adding KMnO 4 Stirring for 3 hours; after heating to 35 ℃ at a speed of 1 ℃/min, maintaining the temperature for 3 hours; then adding deionized water, heating the solution to 90 ℃ at a speed of 3 ℃/min, and preserving heat for 1.5h; then adding deionized water, stirring for 30min, and dripping H 2 O 2 The color of the solution changed from dark brown to yellow; finally, placing the solution in a dialysis bag and dialyzing with deionized water, replacing the deionized water every 12 hours until the solution is dialyzed to be neutral, and then freeze-drying the solution to obtain graphite oxide;
wherein, graphite powder: naNO 3 ：H 2 SO 4 ：KMnO 4 : deionized water: deionized water ratio g: g: mL: g: mL: mL is 10:5:250:40:500:500.
further, the directional freezing mold in the step (2) is a directional freezing mold of the directional freezing device, the directional freezing device comprises a liquid nitrogen container, a conductive copper plate and a directional freezing mold, the liquid nitrogen container is arranged in the horizontal direction, liquid nitrogen can be contained in the liquid nitrogen container, the conductive copper plate comprises a vertical connecting part and a horizontal supporting part which are vertically connected, the vertical connecting part and the horizontal supporting part are made of copper, the horizontal supporting part is arranged in the horizontal direction, the horizontal supporting part is connected with the liquid nitrogen container through the vertical connecting part, the vertical connecting part can be in contact with the liquid nitrogen in the liquid nitrogen container, the upper surface of the horizontal supporting part is detachably connected with the directional freezing mold, the directional freezing mold comprises a bottom plate and a side plate, the side plate is tightly and detachably arranged above the outer edge of the bottom, the bottom plate and the side plate form a hollow interior, the hollow interior of the directional freezing mold can contain a sample to be frozen, the bottom plate of the directional freezing mold is made of copper foil, and the side plate is made of polytetrafluoroethylene;
when the device is used, liquid nitrogen is poured into a position which is three fourths away from the top of the container, a sample is placed in the directional freezing mould, the sample at the bottom of the directional freezing mould starts to crystallize through directional cold conduction of the conductive copper plate, and ice crystals perpendicular to the bottom are formed inside the sample in the inside of the directional freezing mould, so that directional freezing is realized.
Further, the drying time in the step (3) is 20-24 hours, and the drying temperature is 75-85 ℃.
Further, the temperature rising rate of the step (3) to the temperature of 250-350 ℃ is 2-4 ℃/min, and the temperature rising rate of the step (3) to the temperature of 950-1050 ℃ is 4-6 ℃/min.
Further, after the nanofiber/graphite oxide aerogel is taken out in the step (3) and before drying, placing water absorbing paper under the nanofiber/graphite oxide aerogel, and replacing the water absorbing paper for 5-10 min.
The three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic prepared by the preparation method is prepared.
The three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic is applied to aerospace and/or chemical metallurgy and/or nuclear power generation.
The beneficial effects obtained by the invention are as follows:
1. according to the method, the nano fiber/graphite oxide aerogel is taken as a framework, the SiBCN precursor is taken as a filler, pyrolysis carbonization and the cracking and sintering of the SiBCN precursor are simultaneously carried out, and the three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic material is obtained, has excellent high temperature resistance and oxidation resistance, has excellent mechanical properties, and has wide application prospect in the fields of aerospace, chemical metallurgy, nuclear power generation and the like.
2. According to the method, the nano fibers and the graphite oxide are combined more tightly by directional freeze drying, a unique columnar pore structure is formed and stacked, so that the composite aerogel has compression retraction elasticity in three directions, and the strength of the material is higher.
3. The strength of the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material prepared by the invention is greatly improved, the pressure intensity during deformation is more than 4 times that of uncomplexed SiBCN, and the rebound rate is more than 85% when the deformation amount is 10%.
4. Due to the addition of the SiBCN precursor, the shape of the nanofiber/graphite oxide carbon aerogel can be completely restored to the original shape when the nanofiber/graphite oxide carbon aerogel is subjected to larger compression deformation, and the nanofiber/graphite oxide carbon aerogel can maintain superelasticity and has high bearing capacity in a high compression strain state, so that the method has important significance in practical application of micro-nano ceramic fibers.
Drawings
FIG. 1 is a schematic illustration of a structural connection of the directional freezer of the present invention;
FIG. 2 is an SEM image of the three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic material prepared in example 1 of the present invention at different magnifications;
FIG. 3 is an SEM image of the internal structure of a three-dimensional network micro-nano structure silicon-based precursor ceramic material prepared in example 2;
FIG. 4 is an SEM image of the internal structure of the three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic material prepared in the embodiment 3 of the invention;
FIG. 5 is an SEM image of the internal structure of the three-dimensional network micro-nano structure silicon-based precursor ceramic material prepared in comparative example 2;
fig. 6 is a compression rebound diagram of the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material prepared in example 1, the three-dimensional network micro-nano structure material prepared in comparative example 1, the three-dimensional network micro-nano structure silicon-based precursor ceramic material prepared in example 2, and the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material prepared in example 3 when the deformation amount is 10%.
Detailed Description
The present invention will be further described in detail with reference to examples, but the scope of the present invention is not limited to the examples.
The raw materials used in the invention are conventional commercial products unless specified otherwise, the methods used in the invention are conventional methods in the art unless specified otherwise, and the mass of each substance used in the invention is conventional.
A preparation method of a three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic comprises the following steps:
(1) Mixing nanofiber gel with deionized water, and performing ultrasonic treatment to obtain a dispersion liquid with the mass concentration of 0.3-1.0 wt%;
(2) Mixing the dispersion liquid with graphite oxide solution with the mass concentration of 0.3-1.0 wt%, preparing mixed gel by using a freeze-drying method, a hydrothermal method or an ethylenediamine method in the hydrothermal process, placing the mixed gel in a directional freezing mold, and taking out the mixed gel after molding and freeze-drying for 12-14 hours to obtain nanofiber/graphite oxide aerogel;
wherein the mass ratio of the nanofiber gel in the dispersion liquid to the graphene oxide in the graphene oxide aqueous solution is 3-8: 3 to 8;
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 60-80 min in a vacuum environment, taking out the nanofiber/graphite oxide aerogel, drying, and then preserving heat for 4-5 h at 250-350 ℃ in an inert gas environment and then preserving heat for 2-3 h at 950-1050 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material;
wherein the SiBCN precursor solution is a mixture of polyborosilazane and N-hexane, and the volume ratio of polyborosilazane to SiBC N precursor solution is 1:20.
preferably, the time of the ultrasonic wave in the step (1) is 60-70 s, and the power of the ultrasonic wave is 1200-1400W.
Preferably, the freeze-drying method in the step (2) is as follows: ultrasonic treatment is carried out for 30-40 min to gel state with power of 1100-1300W, water bath heating is carried out for 50-70 min at the temperature of 90-95 ℃, and cooling is carried out to room temperature, thus obtaining mixed gel;
alternatively, the hydrothermal method in the step (2) is as follows: ultrasonically crushing for 30-40 min at 150-160W power, reacting for 5-7 h at 120-130 ℃, dialyzing in an ethanol water solution with the mass concentration of 20wt% until floating in the ethanol water solution, and taking out to obtain a mixed gel;
or, the method of adding ethylenediamine in the hydrothermal process in the step (2) is as follows: crushing for 30-40 min with 150-160W power, adding ethylenediamine to regulate pH to 9.8-10.2 while stirring, reacting at 110-130 deg.c for 5-7 hr, dialyzing in 20wt% concentration alcohol solution until floating in the alcohol solution, and taking out to obtain mixed gel.
Preferably, the preparation method of graphite oxide in the graphite oxide solution in the step (2) comprises the following steps:
graphite powder and NaNO 3 Mixing, placing in ice-water bath, adding H 2 SO 4 Adding KMnO within 40min 4 Continuously stirring during the process, adding KMnO 4 Stirring for 3 hours; to be used forAfter the temperature is raised to 35 ℃ at the speed of 1 ℃/min, maintaining the temperature for 3 hours; then adding deionized water, heating the solution to 90 ℃ at a speed of 3 ℃/min, and preserving heat for 1.5h; then adding deionized water, stirring for 30min, and dripping H 2 O 2 The color of the solution changed from dark brown to yellow; finally, placing the solution in a dialysis bag and dialyzing with deionized water, replacing the deionized water every 12 hours until the solution is dialyzed to be neutral, and then freeze-drying the solution to obtain graphite oxide;
wherein, graphite powder: naNO 3 ：H 2 SO 4 ：KMnO 4 : deionized water: deionized water ratio g: g: mL: g: mL: mL is 10:5:250:40:500:500.
preferably, the directional freezing mold in the step (2) is a directional freezing mold of a directional freezing device, the directional freezing device comprises a liquid nitrogen container, a conductive copper plate and a directional freezing mold, the liquid nitrogen container is arranged in the horizontal direction, liquid nitrogen can be contained in the liquid nitrogen container, the conductive copper plate comprises a vertical connecting part and a horizontal supporting part which are vertically connected, the vertical connecting part and the horizontal supporting part are both made of copper, the horizontal supporting part is arranged in the horizontal direction, the horizontal supporting part is connected with the liquid nitrogen container through the vertical connecting part, the vertical connecting part can be in contact with the liquid nitrogen in the liquid nitrogen container, the upper surface of the horizontal supporting part is detachably connected with the directional freezing mold, the directional freezing mold comprises a bottom plate and a side plate, the side plate is tightly and detachably arranged above the outer edge of the bottom, the hollow interior of the directional freezing mold can contain a sample to be frozen, the bottom plate of the directional freezing mold is made of copper foil, and the side plate is made of polytetrafluoroethylene;
when the device is used, liquid nitrogen is poured into a position which is three fourths away from the top of the container, a sample is placed in the directional freezing mould, the sample at the bottom of the directional freezing mould starts to crystallize through directional cold conduction of the conductive copper plate, and ice crystals perpendicular to the bottom are formed inside the sample in the inside of the directional freezing mould, so that directional freezing is realized.
Preferably, the drying time in the step (3) is 20-24 hours, and the drying temperature is 75-85 ℃.
Preferably, the heating rate of the step (3) to the temperature of 250-350 ℃ is 2-4 ℃/min, and the heating rate of the step (3) to the temperature of 950-1050 ℃ is 4-6 ℃/min.
Preferably, after the nanofiber/graphite oxide aerogel is taken out in the step (3) and before drying, the water absorbing paper is placed under the nanofiber/graphite oxide aerogel, and the water absorbing paper is replaced for 5-10 min.
The three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic prepared by the preparation method is prepared.
The three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic is applied to aerospace and/or chemical metallurgy and/or nuclear power generation.
Specifically, the related preparation and detection are as follows:
the sources of purchase for the raw materials in the examples below were as follows:
nanofiber gels were purchased from zhongshan nanofibrillar new materials limited.
Sodium nitrate (NaNO) 3 Analytically pure), concentrated sulfuric acid (H 2 SO 4 Analytically pure), potassium permanganate (KMnO 4 Analytically pure) was purchased from the company, metropolis, inc.
Hydrogen peroxide (H) 2 O 2 Analytically pure) was purchased from Tianjin, jiang Tian chemical technology Co., ltd.
The purity of the graphite powder is more than or equal to 99.95 percent and is provided by Shanghai A Ding Shiji Co.
Ethylenediamine (EDA, analytically pure) was purchased from sienna biochemical technologies limited.
SIBCN (60% strength in n-hexane solution of polyborosilazane) was purchased from the institute of chemistry, national academy of sciences.
The preparation method of Graphene Oxide (GO) in the following embodiment adopts an improved Hummer method, and specifically comprises the following steps:
10g of graphite powder and 5g of NaNO 3 Mixing, placing in ice-water bath, slowly adding 250mLH 2 SO 4 Adding 40g KMnO in 40min 4 Continuously stirring during the process, adding KMnO 4 And then stirred for 3 hours. After heating to 35℃at a rate of 1℃per minute, this temperature was maintained for 3 hours. Then, 500mL of deionized water was added, and the solution was warmed to 90℃at a rate of 3℃per minute and incubated for 1.5h. Then adding 500mL deionized water, stirring for 30min, and dripping H 2 O 2 The color (analytically pure) to the solution changed from dark brown to yellow. Finally, the solution is placed in a dialysis bag and dialyzed with deionized water, the deionized water is replaced every 12 hours until the solution is dialyzed to be neutral, and then the solution is freeze-dried to obtain graphite oxide.
Example 1
The preparation method of the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic comprises the following steps:
(1) Mixing nanofiber gel and deionized water, and performing ultrasonic treatment at a power of 1200W for 60 seconds to obtain a dispersion liquid with a mass concentration of 0.6 wt%;
(2) Mixing the dispersion liquid and graphite oxide solution with the mass concentration of 0.8wt%, carrying out ultrasonic treatment at the power of 1200W for 30min to gel, heating in a water bath at 90 ℃ for 60min, and cooling to room temperature to obtain a mixed gel. And (3) forming the mixed gel by a directional freezing device, and freeze-drying for 12 hours to obtain the nanofiber/graphite oxide aerogel, wherein the mass ratio of the nanofiber gel in the dispersion liquid to the graphite oxide in the graphite oxide solution is 6:8 in terms of parts by weight.
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 60min in a vacuum environment, taking out, placing a piece of absorbent paper under the nanofiber/graphite oxide aerogel for 8min, and replacing the absorbent paper once to suck out the redundant SiBC N precursor solution. Drying the ceramic material in an oven at 80 ℃ for 24 hours, then heating the ceramic material to 300 ℃ at 3 ℃/min in a tubular furnace under an argon environment, preserving heat for 4 hours at 300 ℃ (the argon flow rate is 40 mL/min), heating the ceramic material to 1000 ℃ at 5 ℃/min, preserving heat for 2 hours at 1000 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material, wherein almost no dust and slag are removed during compression, so that the respiratory system of constructors is protected, and the environmental pollution is reduced; SIBCN is added, the high temperature limit can exceed 1000 ℃, so that the application range of the aerogel is enlarged; even in a state of high compressive strain, the composite material also has the mechanical properties of good strength, super elasticity maintenance, high bearing capacity and the like. Wherein the SiBCN precursor solution is a mixture of polyborosilazane and n-hexane, and the ratio of the volume parts of polyborosilazane to the volume parts of SiB CN precursor solution in the SiBCN precursor solution is 1:20.
the directional freezing device comprises a liquid nitrogen container 1, a conductive copper plate and a directional freezing mold, wherein the liquid nitrogen container is arranged in the liquid nitrogen container along the horizontal direction, the liquid nitrogen container can be filled with liquid nitrogen, the conductive copper plate comprises a vertical connecting portion 2 and a horizontal supporting portion 3 which are vertically connected, the vertical connecting portion and the horizontal supporting portion are made of copper, the horizontal supporting portion is arranged in the horizontal direction, the horizontal supporting portion is connected with the liquid nitrogen container through the vertical connecting portion, the vertical connecting portion can be in contact with the liquid nitrogen in the liquid nitrogen container, the vertical connecting portion can conduct the temperature of the liquid nitrogen to the horizontal supporting portion, the horizontal supporting portion conducts the temperature to the directional freezing mold, the directional freezing mold is detachably arranged on the upper surface of the horizontal supporting portion, the directional freezing mold comprises a bottom plate 4 and a side plate 5, the side plate is detachably and vertically arranged above the outer edge of the bottom, the bottom plate and the side plate form a hollow interior (not numbered in the drawing), the hollow interior of the directional freezing mold can contain a sample to be frozen, the bottom plate of the directional freezing mold is made of polytetrafluoroethylene, and the copper foil is made of the polytetrafluoroethylene.
When the device is used, liquid nitrogen is poured into a position which is three fourths away from the top of the container, a sample is placed in the directional freezing mould, the sample is placed on the copper plate, the sample at the bottom of the directional freezing mould starts to crystallize through directional cold conduction of the copper plate, and ice crystals perpendicular to the bottom are formed inside the sample in the interior of the freezing mould, so that directional freezing is realized.
As shown in fig. 2, a layer of SiB CN is attached to the surface of the three-dimensional network micro-nano structure silicon-based precursor super-high temperature elastic ceramic material, and the SiB CN is uniformly distributed on the surface of the three-dimensional network micro-nano structure silicon-based precursor super-high temperature elastic ceramic material in a punctiform manner.
Example 2
A method for preparing a three-dimensional network micro-nano structure silicon-based precursor ceramic material comprises the following steps:
(1) Mixing nanofiber gel and deionized water, and performing ultrasonic treatment at a power of 1200W for 60 seconds to obtain a dispersion liquid with a mass concentration of 0.8 wt%;
(2) Mixing the dispersion liquid with graphite oxide solution with the mass concentration of 0.6wt%, performing ultrasonic crushing for 30min with a cell crusher at the power of 150W, putting into a hydrothermal kettle for reaction at 120 ℃ for 6h, dialyzing in ethanol water solution with the mass concentration of 20wt% until floating in the ethanol water solution, and taking out to obtain a mixed gel. And (3) forming the mixed gel by a directional freezing device, and freeze-drying for 12 hours to obtain the nanofiber/graphite oxide aerogel, wherein the mass ratio of the nanofiber gel in the dispersion liquid to the graphite oxide in the graphite oxide solution is 4:3.
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 60min in a vacuum environment, taking out, placing a piece of absorbent paper under the nanofiber/graphite oxide aerogel for 8min, and replacing the absorbent paper once to suck out the redundant SiBC N precursor solution. Drying the mixture for 24 hours at 80 ℃, then heating the mixture to 300 ℃ at 3 ℃/min in a tubular furnace under an argon environment, preserving heat for 4 hours at 300 ℃ (argon flow rate is 40 mL/min), heating the mixture to 1000 ℃ at 5 ℃/min, and preserving heat for 2 hours at 1000 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ceramic material, wherein the SiBCN precursor solution is a mixture of polyborosilazane and n-hexane, and the ratio of the volume parts of polyborosilazane to the volume parts of the Si BCN precursor solution in the SiBCN precursor solution is 1:20.
as shown in fig. 3, the nanofiber/graphite oxide aerogel material obtained in example 2 has a relatively disordered internal structure, irregular pore structure and uneven pore size, and a layered structure with regular arrangement exists in a partial region, but sheets in other directions are intersected with each other, so that the macroscopic compression resilience can reach more than 60%.
Example 3
The preparation method of the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material comprises the following steps:
(1) Mixing nanofiber gel and deionized water, and performing ultrasonic treatment at a power of 1200W for 60 seconds to obtain a dispersion liquid with a mass concentration of 0.8 wt%;
(2) Mixing the dispersion liquid with a graphite oxide solution with the mass concentration of 0.4wt%, performing ultrasonic crushing for 30min with a cell crusher at the power of 150W, adding ethylenediamine under the stirring condition to adjust the pH value to 10, putting into a hydrothermal kettle for reaction at 120 ℃ for 6h, dialyzing in an ethanol water solution with the mass concentration of 20wt% until the mixture floats in the ethanol water solution, and taking out to obtain a mixed gel. And (3) forming the mixed gel by a directional freezing device, and freeze-drying for 12 hours to obtain the nanofiber/graphite oxide aerogel, wherein the mass ratio of the nanofiber gel in the dispersion liquid to the graphite oxide in the graphite oxide solution is 3:4.
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 60min in a vacuum environment, taking out, placing a piece of absorbent paper under the nanofiber/graphite oxide aerogel for 8min, and replacing the absorbent paper once to suck out the redundant SiBC N precursor solution. Drying the mixture for 24 hours at 80 ℃, then heating the mixture to 300 ℃ at 3 ℃/min in a tubular furnace under an argon environment, preserving heat for 4 hours at 300 ℃ (argon flow rate is 40 mL/min), heating the mixture to 1000 ℃ at 5 ℃/min, and preserving heat for 2 hours at 1000 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ceramic material, wherein the SiBCN precursor solution is a mixture of polyborosilazane and n-hexane, and the ratio of the volume parts of polyborosilazane to the volume parts of the Si BCN precursor solution in the SiBCN precursor solution is 1:20.
as shown in FIG. 4, the obtained three-dimensional network micro-nano structure silicon-based precursor ceramic material has uniform pore size distribution, and the stacked structure of spherical pores is arranged between the sheets. The ethylenediamine is more tightly bound to the graphite oxide, thereby resulting in a more uniformly distributed lamellar structure. Holes appear in the lamellae due to the fact that during the joining of the graphite oxide, some of the carboxylic groups of the nanofibres penetrate the lamellar structure.
Comparative example 1
The preparation method of the three-dimensional network micro-nano structure composite material comprises the following steps: and (3) placing the nanofiber/graphite oxide aerogel obtained in the step (2) in the example (1) into a tube furnace, heating to 300 ℃ at 3 ℃/min under an argon environment (argon flow rate is 40 mL/min), preserving heat for 4 hours at 300 ℃ (argon flow rate is 40 mL/min), heating to 1000 ℃ at 5 ℃/min, and preserving heat for 2 hours at 1000 ℃ to obtain the three-dimensional network micro-nano structural material.
As shown in fig. 6, compared with comparative example 1, the rebound rate of example 1 is slightly reduced after the SiBCN is compounded, but the rebound rate is still above 85% when the deformation amount is 10%, and after the SiBCN is compounded, the pressure required by the three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic material prepared in example 1 when the deformation amount is 10% is more than 4 times that of the three-dimensional network micro-nano structure material prepared in comparative example 1.
Comparative example 2
A preparation method of a three-dimensional network micro-nano structure silicon-based precursor ceramic material comprises the following steps:
(1) Mixing the nanofiber gel with deionized water, and performing ultrasonic treatment at 1300W for 70 seconds to obtain a dispersion liquid with the mass concentration of 0.8 wt%;
(2) Mixing the dispersion liquid with graphite oxide solution with the mass concentration of 0.8wt%, carrying out ultrasonic treatment at 1300W for 40min to gel state, heating in a water bath at 95 ℃ for 70min, and cooling to room temperature to obtain a mixed gel. And (3) forming the mixed gel by a directional freezing device, and freeze-drying for 14 hours to obtain the nanofiber/graphite oxide aerogel, wherein the mass ratio of the nanofiber gel in the dispersion liquid to the graphite oxide in the graphite oxide solution is 6:8.
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 80min in a vacuum environment, taking out, placing a piece of absorbent paper under the nanofiber/graphite oxide aerogel for 10min, and replacing the absorbent paper once to suck out the redundant SiB CN precursor solution. Drying for 24h at 85 ℃ in an oven, heating to 350 ℃ at 4 ℃/min in a tubular furnace under argon environment, preserving heat for 5h at 350 ℃ (argon flow rate is 40 mL/min), heating to 1050 ℃ at 6 ℃/min, and preserving heat for 3h at 1050 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ceramic material. Wherein the SiBCN precursor solution is a mixture of polyborosilazane and n-hexane, and the volume ratio of polyborosilazane to SiBCN precursor solution is 12:20
As shown in fig. 5, when the SiBCN precursor solution is immersed, it can be seen that SiBCN fills the pores between the fiber sheets, and as the concentration of the precursor is too high (i.e., 60%), certain stress occurs in the SiBCN during the splitting process, and the strength of the fiber matrix is insufficient to support the stress, cracks occur, that is, the fiber sheets are broken through by the cracks generated during the splitting process of the precursor.
Comparative example 3
The preparation method of the three-dimensional network micro-nano structure comprises the following steps:
1) Mixing nanofiber gel and deionized water, and performing ultrasonic treatment at a power of 1200W for 60 seconds to obtain a dispersion liquid with a mass concentration of 0.8 wt%;
2) Mixing the dispersion liquid and graphite oxide solution with mass concentration of 0.4wt%, ultrasonic treating with 1200W power for 30min to gel state, heating in water bath at 90 deg.c for 60min, and cooling to room temperature to obtain mixed gel. After the mixed gel is molded by a directional freezing device, freeze-drying is carried out for 12 hours, and the nanofiber/graphite oxide aerogel is obtained, wherein the ratio of nanofiber gel in the dispersion liquid to graphite oxide in the graphite oxide solution is 3:4.
the nanofiber/graphite oxide aerogel obtained from the wood fiber gel obtained in comparative example 3 had a loose structure and could not be formed into a block structure.
As can be seen from fig. 6, the pressure and the rebound rate in the example 3 are obviously improved by the pressure and the rebound rate in the example 3 added with ethylenediamine, the rebound rate is also more than 85%, and the pressure is only one half of that in the example 1.
As can be seen from comparative examples 1, 3, 1 and 3, the SiBCN precursor solution and the thermal insulation at 250-350 ℃ for 4-5 h and the thermal insulation at 950-1050 ℃ for 2-3 h in the inert gas environment in the preparation method have synergistic effects, so that the correlation performance of the prepared three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic can be synergistically improved.
Although embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments.
Claims (9)
1. A preparation method of a three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic is characterized by comprising the following steps of: the method comprises the following steps:
(1) Mixing nanofiber gel with deionized water, and performing ultrasonic treatment to obtain a dispersion liquid with the mass concentration of 0.3-1.0wt%;
(2) Mixing the dispersion liquid and graphite oxide solution with the mass concentration of 0.3-1.0wt%, preparing a mixed gel by using a freeze-drying method, a hydrothermal method or an ethylenediamine method in the hydrothermal process, placing the mixed gel in a directional freezing mold, and taking out the mixed gel after molding and freeze-drying for 12-14 hours to obtain nanofiber/graphite oxide aerogel;
the mass ratio of the nanofiber gel in the dispersion to the graphene oxide in the graphene oxide aqueous solution is 3-8: 3-8;
(3) Immersing the nanofiber/graphite oxide aerogel into SiBCN precursor solution for 60-80 min in a vacuum environment, taking out the nanofiber/graphite oxide aerogel, drying, and then preserving heat for 4-5 h at 250-350 ℃ in an inert gas environment, and preserving heat for 2-3 h at 950-1050 ℃ to obtain the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic material;
wherein the SiBCN precursor solution is a mixture of polyborosilazane and n-hexane, and the volume ratio of polyborosilazane to SiBCN precursor solution is 1:20, a step of;
the freeze-drying method in the step (2) comprises the following steps: ultrasonic treatment is carried out for 30-40 min to gel state with power of 1100-1300W, water bath heating is carried out for 50-70 min at the temperature of 90-95 ℃, and cooling is carried out to room temperature, thus obtaining mixed gel;
alternatively, the hydrothermal method in the step (2) is as follows: ultrasonically crushing for 30-40 min at a power of 150-160W, reacting for 5-7 h at 120-130 ℃, dialyzing in an ethanol water solution with a mass concentration of 20wt% until the gel floats in the ethanol water solution, and taking out to obtain a mixed gel;
or, the method of adding ethylenediamine in the hydrothermal process in the step (2) is as follows: crushing for 30-40 min with 150-160W power by ultrasonic, adding ethylenediamine under stirring to adjust the pH to 9.8-10.2, reacting for 5-7 h at 110-130 ℃, dialyzing in an ethanol water solution with the mass concentration of 20wt% until floating in the ethanol water solution, and taking out to obtain the mixed gel.
2. The method for preparing the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, which is characterized by comprising the following steps of: the ultrasonic time in the step (1) is 60-70 s, and the ultrasonic power is 1200-1400W.
3. The method for preparing the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, which is characterized by comprising the following steps of: the preparation method of the graphite oxide in the graphite oxide solution in the step (2) comprises the following steps:
graphite powder and NaNO 3 Mixing, placing in ice-water bath, adding H 2 SO 4 Adding KMnO within 40min 4 Continuously stirring during the process, adding KMnO 4 Stirring for 3 hours; after heating to 35 ℃ at a speed of 1 ℃/min, maintaining the temperature for 3 hours; then adding deionized water, heating the solution to 90 ℃ at a speed of 3 ℃/min, and preserving heat for 1.5h; then adding deionized water, stirring for 30min, and dripping H 2 O 2 The color of the solution changed from dark brown to yellow; finally, placing the solution in a dialysis bag and dialyzing with deionized water, replacing the deionized water every 12 hours until the solution is dialyzed to be neutral, and then freeze-drying the solution to obtain graphite oxide;
wherein, graphite powder: naNO 3 ：H 2 SO 4 ：KMnO 4 Ratio g: g: mL: g is 10:5:250:40.
4. the method for preparing the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, which is characterized by comprising the following steps of: the directional freezing mold in the step (2) is a directional freezing mold of a directional freezing device, the directional freezing device comprises a liquid nitrogen container, a conductive copper plate and a directional freezing mold, the liquid nitrogen container is arranged in the horizontal direction, liquid nitrogen can be contained in the liquid nitrogen container, the conductive copper plate comprises a vertical connecting part and a horizontal supporting part which are vertically connected, the vertical connecting part and the horizontal supporting part are made of copper, the horizontal supporting part is arranged in the horizontal direction, the horizontal supporting part is connected with the liquid nitrogen container through the vertical connecting part, the vertical connecting part can be in contact with the liquid nitrogen in the liquid nitrogen container, the upper surface of the horizontal supporting part is detachably connected with the directional freezing mold, the directional freezing mold comprises a bottom plate and a side plate, the side plate is tightly and detachably arranged above the outer edge of the bottom, the hollow interior of the directional freezing mold can contain a sample to be frozen, the bottom plate of the directional freezing mold is made of copper foil, and the side plate is made of polytetrafluoroethylene;
when the device is used, liquid nitrogen is poured into a position which is three fourths away from the top of the container, a sample is placed in the directional freezing mould, the sample at the bottom of the directional freezing mould starts to crystallize through directional cold conduction of the conductive copper plate, and ice crystals perpendicular to the bottom are formed inside the sample in the inside of the directional freezing mould, so that directional freezing is realized.
5. The method for preparing the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, which is characterized by comprising the following steps of: and (3) drying for 20-24 hours at 75-85 ℃.
6. The method for preparing the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic, which is characterized by comprising the following steps of: and (3) heating to 250-350 ℃ at a heating rate of 2-4 ℃/min, and heating to 950-1050 ℃ at a heating rate of 4-6 ℃/min.
7. The method for preparing the three-dimensional network micro-nano structure silicon-based precursor ultrahigh temperature elastic ceramic according to any one of claims 1 to 6, which is characterized in that: and (3) placing water absorbing paper under the nanofiber/graphite oxide aerogel after taking out the nanofiber/graphite oxide aerogel and before drying, and replacing the water absorbing paper for 5-10 min.
8. The three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic prepared by the preparation method according to any one of claims 1 to 7.
9. The use of the three-dimensional network micro-nano structure silicon-based precursor ultra-high temperature elastic ceramic as claimed in claim 8 in aerospace, chemical metallurgy or nuclear power generation.
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