CN110483053B - Preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption - Google Patents
Preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption Download PDFInfo
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Abstract
The invention relates to a preparation method of SiC nanowire/SiC porous ceramic, in particular to a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption3、Fe(NO3)3And Ni (NO)3)2And the like metal salts; soluble silicon resin and a catalyst can be added in a gel casting process, and the SiC nanowires are generated by direct in-situ reaction during sintering; the organic silicon resin is cracked to generate carbon and SiO2, and SiC nanowires can be generated in situ in the subsequent sintering process, so that the mechanical property and the wave-absorbing property of the porous SiC are improved; the high volume fraction of connected pores formed after gel casting also promotes the V-L-S growth of the SiC nanowires.
Description
Technical Field
The invention relates to a preparation method of SiC nanowire/SiC porous ceramic, in particular to a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption.
Background
The SiC nanowire has high specific strength and specific modulus, can achieve effective reinforcing and toughening effects in the composite material, and can regulate and control the electromagnetic performance by changing the microscopic morphology of the SiC nanowire. The SiC nanowire/SiC porous ceramic with different microscopic morphologies can be prepared to obtain the wave-transmitting characteristic of a wide frequency band and excellent mechanical properties.
The gel-casting process can be classified into water-based and non-water-based depending on the solvent used. The water-based gel casting is usually used for preparing high-density ceramics, the gel prepared by taking water as a solvent has higher strength, but the blank shrinks greatly in the drying process, and the high-porosity blank is difficult to prepare; the gel prepared by the organic solvent has smaller drying shrinkage and can be used for preparing high-porosity blanks, but the gel prepared in the organic solvent has low polymerization degree and low blank strength and is inconvenient for industrial production.
Disclosure of Invention
The invention aims to provide a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption, which can realize the integrated preparation of the SiC nanowire/SiC porous ceramic and improve the mechanical property and the wave absorption property of porous SiC.
The purpose of the invention is realized by the following technical scheme:
a method for preparing SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that soluble silicon resin and a catalyst are added in the process of preparing a ceramic green body by a gel injection molding method, and the SiC nanowire is generated by in-situ reaction during sintering.
As further optimization of the technical scheme, the invention discloses a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption, which comprises the following steps:
the method comprises the following steps: ball-milling and mixing the SiC powder and the sintering aid for 12-24 h, wherein the ball-milling medium is ethanol, and sieving the mixture through a 100-200-mesh sieve after ball-milling and drying;
step two: ball-milling and mixing a solvent, ceramic powder, a dispersing agent, a monomer, a cross-linking agent, soluble silicon resin and a catalyst for 12-24 hours to form slurry;
step three: placing the mixed slurry into vacuum, stirring and removing bubbles for 10min, adding an initiator and a catalyst into the slurry, stirring for 10min, then injecting into a mold, heating to 50-60 ℃, and keeping the temperature for 0.5-2 h to obtain gel;
step four: drying the demoulded blank in an oven at 50-60 ℃, heating to 200 ℃ after complete drying, and keeping the temperature for 2h to crosslink and solidify the silicon resin in the blank;
step five: placing the blank into a cracking furnace for rubber discharge;
step six: and sintering the green body after cracking and glue discharging in a pneumatic furnace.
As further optimization of the technical scheme, the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that the volume ratio of the ceramic powder to the solvent is 1: 1.5-9, the mass ratio of the dispersing agent to the ceramic powder is 1: 49-124, the mass ratio of the monomer to the ceramic powder is 1: 6-33, the mass ratio of the crosslinking agent to the monomer is 1: 20-30, the mass ratio of the soluble silicon resin to the ceramic powder is 1: 19-99, and the mass ratio of the catalyst to the solvent is 1: 97-99.9.
As further optimization of the technical scheme, the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption comprises the steps of using ethanol, isopropanol and tert-butyl alcohol as solvents, using polyvinylpyrrolidone as a dispersing agent, using acrylamide as a monomer, using N, N-methylene bisacrylamide as a crosslinking agent, using soluble silicon resin soluble in ethanol, isopropanol and tert-butyl alcohol as a catalyst, and using ferrocene and FeCl as a catalyst3、Fe(NO3)3And Ni (NO)3)2。
As further optimization of the technical scheme, the invention discloses a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption, and the sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.6-0.8.
As further optimization of the technical scheme, the invention relates to a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption.
As further optimization of the technical scheme, the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that the mass ratio of the initiator to the monomer is 1: 3-10, and the mass ratio of the catalyst to the monomer is 1: 30-200.
As further optimization of the technical scheme, the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that the glue discharging temperature is 550-650 ℃, the heating rate is 0.3 ℃/min, the heat preservation time is 2 hours, and the atmosphere is nitrogen or argon.
According to the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption, the sintering step is that the temperature is increased to 1500 ℃ at a speed of 10 ℃/min and is kept for 0.5-1 h, then the temperature is increased to 1700-1900 ℃ at a speed of 5 ℃/min and is kept for 1-4 h, the sintering atmosphere is argon, and the pressure is 0.4-1 MPa.
As further optimization of the technical scheme, the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that the mass ratio of the SiC powder to the sintering aid is 1: 89-99.
The preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption has the beneficial effects that:
the invention relates to a preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption, which can add soluble silicon resin and a catalyst in a gel casting process, and directly react in situ to generate SiC nanowires during sintering; the organic silicon resin generates carbon and SiO after cracking2The SiC nanowires can be generated in situ in the subsequent sintering process, so that the mechanical property and the wave-absorbing property of the porous SiC are improved; the high volume fraction of the connected pores formed after gel injection molding also promotes the growth of V-L-S of the SiC nanowires, the distribution state and the morphology of the SiC nanowires in the porous SiC ceramics can be changed by adjusting the sintering process and the content of the soluble silicon resin and the catalyst, the wave absorbing performance of the material is further regulated, the strength of the ceramic green body can be greatly improved after the added soluble silicon resin is cured at low temperature, and the subsequent processing is convenient.
Drawings
The invention is described in further detail below with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a first schematic view of the microstructure of SiC nanowire/SiC porous ceramic of the present invention;
FIG. 2 is a second schematic view of the microstructure of the SiC nanowire/SiC porous ceramic of the present invention;
FIG. 3 is a schematic diagram of the wave-absorbing property of the SiC nanowire/SiC porous ceramic of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The first embodiment is as follows:
in the following, the embodiment is described with reference to fig. 1 to 3, and a method for preparing SiC nanowire/SiC porous ceramic for high temperature wave absorption is provided, in which soluble silicone resin and a catalyst are added in a process of preparing a ceramic green body by using a gel injection molding method, and SiC nanowires are generated by in-situ reaction during sintering.
The preparation method comprises the following steps:
the method comprises the following steps: ball-milling and mixing the SiC powder and the sintering aid for 12-24 h, wherein the ball-milling medium is ethanol, and sieving the mixture through a 100-200-mesh sieve after ball-milling and drying; preferably, SiC powder and a sintering aid are mixed by ball milling for 12 hours, the mixture is dried and sieved by a 200-mesh sieve, the ball milling medium is ethanol, the mass ratio of the sintering aid to SiC is 1:97, and the sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.6; or preferably, ball milling and mixing the SiC powder and the sintering aid for 24 hours, drying and then sieving with a 200-mesh sieve, wherein the ball milling medium is ethanol, the mass ratio of the sintering aid to the SiC is 1:99, and the sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.8.
Step two: ball-milling and mixing a solvent, ceramic powder, a dispersing agent, a monomer, a cross-linking agent, soluble silicon resin and a catalyst for 12-24 hours to form slurry, wherein the solvent is alcohol such as ethanol, isopropanol and tert-butanolThe dispersant is polyvinylpyrrolidone, the monomer is acrylamide, the cross-linking agent is N, N-methylene bisacrylamide, the soluble silicone resin is alcohol solvents soluble in ethanol, isopropanol, tert-butanol and the like, and the catalyst is ferrocene and FeCl3、Fe(NO3)3And Ni (NO)3)2And the like metal salts; the content of the soluble silicon resin can control the number of SiC nanowires in the porous SiC ceramic, and as the content of the soluble silicon resin and the content of the catalyst in the sample shown in FIG. 2 are higher, more SiC nanowires are generated. The sample shown in fig. 1 has a higher sintering temperature and a faster temperature rise rate, and can reach a straighter SiC nanowire, while the sample in fig. 2 has a slower temperature rise rate due to a lower sintering temperature, and a bent SiC nanowire is obtained. The more the content of the SiC nanowires is, the better the wave absorbing performance of the material is. The material containing the straight SiC nano-wire has better mechanical property and slightly lower wave-absorbing property.
Step three: placing the mixed slurry into vacuum, stirring and removing bubbles for 10min, adding an initiator and a catalyst into the slurry, stirring for 10min, then injecting into a mold, heating to 50-60 ℃, and keeping the temperature for 0.5-2 h to obtain gel; preferably heating to 60 ℃, preserving heat for 2h for gelation, wherein the initiator is ammonium persulfate, the mass ratio of the initiator to the monomer is 1:3, the catalyst is tetramethylethylenediamine, and the mass ratio of the catalyst to the monomer is 1: 30; or heating to 50 ℃ and preserving the temperature for 2h for gelation, wherein the initiator is ammonium persulfate, the mass ratio of the initiator to the monomer is 1:3, the catalyst is tetramethylethylenediamine, and the mass ratio of the catalyst to the monomer is 1: 30.
Step four: drying the demoulded blank in an oven at 50-60 ℃, heating to 200 ℃ after complete drying, and keeping the temperature for 2h to crosslink and solidify the silicon resin in the blank;
step five: placing the blank into a cracking furnace for rubber discharge;
step six: and sintering the green body after cracking and glue discharging in a pneumatic furnace.
The sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.6-0.8; ball milling of preferable SiC powder and sintering aidMixing for 12h, Y2O3And Al2O3The mass ratio of the SiC powder to the sintering aid is 1:0.6, or the SiC powder and the sintering aid are ball-milled and mixed for 24 hours, Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.8.
The volume ratio of the ceramic powder to the solvent is 1: 1.5-9, the mass ratio of the dispersing agent to the ceramic powder is 1: 49-124, the mass ratio of the monomer to the ceramic powder is 1: 6-33, the mass ratio of the crosslinking agent to the monomer is 1: 20-30, the mass ratio of the soluble silicon resin to the ceramic powder is 1: 19-99, and the mass ratio of the catalyst to the solvent is 1: 97-99.9; preferably, the volume ratio of the ceramic powder to the ethanol is 1:9, the mass ratio of the polyvinylpyrrolidone to the ceramic powder is 1:49, the mass ratio of the monomer to the ceramic powder is 1:6, the mass ratio of the crosslinking agent to the monomer is 1:30, the mass ratio of the soluble silicone resin to the ceramic powder is 1:19, and the mass ratio of the catalyst to the solvent is 1: 97; or the volume ratio of the ceramic powder to the ethanol is 1:1.5, the mass ratio of the polyvinylpyrrolidone to the ceramic powder is 1:124, the mass ratio of the monomer to the ceramic powder is 1:6, the mass ratio of the crosslinking agent to the monomer is 1:30, the mass ratio of the soluble silicon resin to the ceramic powder is 1:99, and the mass ratio of the catalyst to the solvent is 1: 99.
The initiator added into the slurry is ammonium persulfate, and the catalyst added into the slurry is tetramethylethylenediamine.
The mass ratio of the initiator to the monomer is 1: 3-10, and the mass ratio of the catalyst to the monomer is 1: 30-200.
The glue discharging temperature is 550-650 ℃, the heating rate is 0.3 ℃/min, the heat preservation time is 2 hours, and the atmosphere is nitrogen or argon; preferably, the blank body is placed into a cracking furnace for glue discharging, the glue discharging temperature is 650 ℃, the heating rate is 0.3 ℃/min, the heat preservation time is 2h, and the atmosphere is argon; or placing the blank body into a cracking furnace for glue discharging, wherein the glue discharging temperature is 550 ℃, the heating rate is 0.5 ℃/min, the heat preservation time is 1h, and the atmosphere is argon.
The sintering step comprises the steps of heating to 1500 ℃ at a speed of 10 ℃/min, preserving heat for 0.5-1 h, heating to 1700-1900 ℃ at a speed of 5 ℃/min, and preserving heat for 1-4 h; preferably, the cracked blank is placed in an air pressure furnace for sintering, the temperature is raised to 1500 ℃ at the speed of 10 ℃/min and is preserved for 0.5h, then the temperature is raised to 1800 ℃ at the speed of 5 ℃/min and is preserved for 2h, the sintering atmosphere is argon, and the pressure is 0.4 MPa; or placing the cracked blank body in an air pressure furnace for sintering, heating to 1500 ℃ at the speed of 10 ℃/min, preserving heat for 1h, heating to 1900 ℃ at the speed of 5 ℃/min, preserving heat for 2h, wherein the sintering atmosphere is argon and the pressure is 0.4MPa, and the sintering atmosphere is argon and the pressure is 0.4-1 MPa.
The mass ratio of the SiC powder to the sintering aid is 1: 89-99; preferably, the mass ratio of the sintering aid to the SiC is 1:97, or the mass ratio of the sintering aid to the SiC is 1: 99.
The second embodiment is as follows:
the following description of the embodiment is provided with reference to fig. 1 to 3, and the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that soluble silicone resin and a catalyst are added in the process of preparing a ceramic green body by using a gel injection molding method, and the SiC nanowire is generated by in-situ reaction during sintering, and the preparation method comprises the following steps:
the method comprises the following steps: ball-milling and mixing SiC powder and a sintering aid for 12h, drying and sieving with a 200-mesh sieve, wherein the ball-milling medium is ethanol, the mass ratio of the sintering aid to SiC is 1:97, and the sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.6.
Step two: mixing ethanol, ceramic powder, polyvinylpyrrolidone, monomer, cross-linking agent, soluble silicone resin and FeCl3Ball-milling and mixing for 12h, wherein the monomer is acrylamide, the cross-linking agent is N, N-methylene bisacrylamide, the volume ratio of the ceramic powder to the ethanol is 1:9, the mass ratio of the N, N-methylene bisacrylamide to the ceramic powder is 1:49, the mass ratio of the monomer to the ceramic powder is 1:6, the mass ratio of the cross-linking agent to the monomer is 1:30, the mass ratio of the soluble silicon resin to the ceramic powder is 1:19, and the mass ratio of the catalyst to the solvent is 1: 97.
Step three: and (2) putting the mixed slurry into vacuum, stirring for 10min to remove bubbles, adding an initiator and a catalyst into the slurry, stirring for 10min, injecting into a mold, heating to 60 ℃, and keeping the temperature for 2h to obtain gel, wherein the initiator is ammonium persulfate, the mass ratio of the initiator to the monomer is 1:3, the catalyst is tetramethylethylenediamine, and the mass ratio of the catalyst to the monomer is 1: 30.
Step four: and (3) demoulding the blank, drying the blank in an oven at 50 ℃, heating to 200 ℃ after complete drying, and keeping the temperature for 2h to crosslink and cure the silicon resin in the blank.
Step five: and (3) placing the blank body into a cracking furnace for glue discharging, wherein the glue discharging temperature is 550 ℃, the heating rate is 0.5 ℃/min, the heat preservation time is 1h, and the atmosphere is argon.
Step six: and (3) sintering the cracked blank in an air pressure furnace, heating to 1500 ℃ at the speed of 10 ℃/min, preserving heat for 0.5h, heating to 1800 ℃ at the speed of 5 ℃/min, preserving heat for 2h, wherein the sintering atmosphere is argon and the pressure is 0.4 MPa.
The third concrete implementation mode:
the following description of the embodiment is provided with reference to fig. 1 to 3, and the preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized in that soluble silicone resin and a catalyst are added in the process of preparing a ceramic green body by using a gel injection molding method, and the SiC nanowire is generated by in-situ reaction during sintering, and the preparation method comprises the following steps:
the method comprises the following steps: ball-milling and mixing SiC powder and a sintering aid for 24 hours, drying and sieving with a 200-mesh sieve, wherein the ball-milling medium is ethanol, the mass ratio of the sintering aid to SiC is 1:99, and the sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.8.
Step two: carrying out ball milling and mixing on ethanol, ceramic powder, polyvinylpyrrolidone, a monomer, a cross-linking agent, soluble silicon resin and ferrocene for 24 hours, wherein the acrylamide is used as a body, the volume ratio of the ceramic powder to the ethanol is 1:1.5, the mass ratio of the polyvinylpyrrolidone to the ceramic powder is 1:124, the mass ratio of the monomer to the ceramic powder is 1:6, the mass ratio of the cross-linking agent to the monomer is 1:30, the mass ratio of the soluble silicon resin to the ceramic powder is 1:99, and the mass ratio of a catalyst to a solvent is 1: 99;
step three: and (2) putting the mixed slurry into vacuum, stirring for 10min to remove bubbles, adding an initiator and a catalyst into the slurry, stirring for 10min, injecting into a mold, heating to 50 ℃, and keeping the temperature for 2h to obtain gel, wherein the initiator is ammonium persulfate, the mass ratio of the initiator to the monomer is 1:3, the catalyst is tetramethylethylenediamine, and the mass ratio of the catalyst to the monomer is 1: 30.
Step four: and (3) demoulding the blank, drying the blank in an oven at 50 ℃, heating to 200 ℃ after complete drying, and keeping the temperature for 2h to crosslink and cure the silicon resin in the blank.
Step five: and (3) placing the blank body into a cracking furnace for glue discharging, wherein the glue discharging temperature is 650 ℃, the heating rate is 0.3 ℃/min, the heat preservation time is 2h, and the atmosphere is argon.
Step six: and (3) sintering the cracked blank in an air pressure furnace, heating to 1500 ℃ at the speed of 10 ℃/min, preserving heat for 1h, heating to 1900 ℃ at the speed of 5 ℃/min, preserving heat for 2h, wherein the sintering atmosphere is argon and the pressure is 0.4 MPa.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and that various changes, modifications, additions and substitutions which are within the spirit and scope of the present invention and which may be made by those skilled in the art are also within the scope of the present invention.
Claims (6)
1. A preparation method of SiC nanowire/SiC porous ceramic for high-temperature wave absorption is characterized by comprising the following steps: adding soluble silicon resin and a catalyst in the process of preparing the ceramic green body by using a gel injection molding method, and carrying out in-situ reaction during sintering to generate SiC nanowires;
the preparation method comprises the following steps:
the method comprises the following steps: ball-milling and mixing the SiC powder and the sintering aid for 12-24 h, wherein the ball-milling medium is ethanol, and sieving the mixture through a 100-200-mesh sieve after ball-milling and drying;
step two: ball-milling and mixing a solvent, ceramic powder, a dispersant, a monomer, a cross-linking agent, soluble silicon resin and a catalyst for 12-24 hours to form slurry, wherein the catalyst is ferrocene or FeCl3、Fe(NO3)3And Ni (NO)3)2；
Step three: placing the mixed slurry into vacuum, stirring and removing bubbles for 10min, adding an initiator and a catalyst into the slurry, stirring for 10min, then injecting into a mold, heating to 50-60 ℃, preserving heat for 0.5-2 h, and gelling, wherein the catalyst added into the slurry is tetramethylethylenediamine;
step four: drying the demoulded blank in an oven at 50-60 ℃, heating to 200 ℃ after complete drying, and keeping the temperature for 2h to crosslink and solidify the silicon resin in the blank;
step five: placing the blank into a cracking furnace for rubber discharge;
step six: placing the green body after cracking and glue discharging in an air pressure furnace for sintering;
in the second step, the volume ratio of the ceramic powder to the solvent is 1: 1.5-9, the mass ratio of the dispersing agent to the ceramic powder is 1: 49-124, the mass ratio of the monomer to the ceramic powder is 1: 6-33, the mass ratio of the cross-linking agent to the monomer is 1: 20-30, the mass ratio of the soluble silicon resin to the ceramic powder is 1: 19-99, and the mass ratio of the catalyst to the solvent is 1: 97-99.9;
in the third step, the mass ratio of the initiator to the monomer is 1: 3-10, and the mass ratio of the catalyst to the monomer is 1: 30-200;
and the sintering step in the sixth step is that the temperature is increased to 1500 ℃ at a speed of 10 ℃/min and is kept for 0.5-1 h, then the temperature is increased to 1700-1900 ℃ at a speed of 5 ℃/min and is kept for 1-4 h, the sintering atmosphere is argon, and the pressure is 0.4-1 MPa.
2. The preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption according to claim 1, which is characterized by comprising the following steps: the solvent is ethanol, isopropanol and tert-butanol, the dispersant is polyvinylpyrrolidone, the monomer is acrylamide, the cross-linking agent is N, N-methylene bisacrylamide, and the soluble silicone resin is soluble in ethanol, isopropanol and tert-butanol.
3. The preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption according to claim 1, which is characterized by comprising the following steps: the sintering aid is Y2O3And Al2O3Composition of powder Y2O3And Al2O3The mass ratio of (A) to (B) is 1: 0.6-0.8.
4. The preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption according to claim 1, which is characterized by comprising the following steps: the initiator added into the slurry is ammonium persulfate.
5. The preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption according to claim 1, which is characterized by comprising the following steps: the glue discharging temperature is 550-650 ℃, the heating rate is 0.3 ℃/min, the heat preservation time is 2h, and the atmosphere is nitrogen or argon.
6. The preparation method of the SiC nanowire/SiC porous ceramic for high-temperature wave absorption according to any one of claims 1 to 5, wherein the preparation method comprises the following steps: the mass ratio of the SiC powder to the sintering aid is 1: 89-99.
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| CN115849948B (en) * | 2022-11-30 | 2023-12-08 | 中国科学院上海硅酸盐研究所 | Fe (Fe) 3 O 4 /SiC nw /Si 3 N 4 Composite wave-absorbing ceramic and preparation method thereof |
| CN117383949B (en) * | 2023-11-10 | 2024-04-02 | 江苏君耀耐磨耐火材料有限公司 | Preparation method of carbon nanofiber toughened refractory material |
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