CN112661531B - Silicon nitride whisker reinforced periclase-spinel-carbon filter and preparation method thereof - Google Patents
Silicon nitride whisker reinforced periclase-spinel-carbon filter and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof. The technical scheme is as follows: mixing the modified periclase-spinel ceramic fine powder, the magnesia fine powder, the modified coal tar asphalt powder, the elemental silicon powder and the sodium carboxymethylcellulose, adding alumina sol, a water reducing agent, a defoaming agent and deionized water, and stirring to obtain ceramic slurry with thixotropy (hereinafter referred to as ceramic slurry). Immersing the pretreated polyurethane foam into the ceramic slurry, taking out the pretreated polyurethane foam, removing the redundant ceramic slurry, maintaining and drying; in N 2 Heating to 1200-1300 ℃ in the atmosphere, preserving heat and cooling; immersing the cooled presintered periclase-spinel-carbon filter in ceramic slurry, centrifuging, drying, and adding N 2 Keeping the temperature in the atmosphere at 1300-1400 ℃ to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter. The product prepared by the invention has the characteristics of high strength, excellent thermal shock stability and excellent filtering effect.
Description
Technical Field
The invention belongs to the technical field of filters. In particular to a silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof.
Background
The metal is a basic material for industrial manufacture, is a 'foundation stone' for national major engineering construction and major equipment manufacture, and has important significance for national economy and national defense construction in developing high-quality metal. The non-metallic inclusion in the metal can seriously affect the strength and the service life of the metal, and the quality of the metal can be effectively improved by removing the non-metallic inclusion and improving the purity of the molten metal. The introduction of a ceramic filter to filter impurities in molten metal in the final step of molten metal casting is an important way for effectively purifying the molten metal and improving the metal quality.
Currently, there is much research on molten metal filters, particularly magnesium and its alloys, and cast steel filters. For example, the patent technology of 'a spinel reinforced magnesia-based foamed ceramic filter and a preparation method thereof' (201810307618.0) adopts magnesia ceramic powder as a raw material, and adds nano aluminum sol, a rheological agent and nano lanthanum oxide to prepare the spinel reinforced magnesia-based foamed ceramic filter. The magnesia ceramic powder adopted by the technology is a compact raw material, so that the surface structure of the framework of the filter is relatively compact, the adsorption capacity to impurities is limited, and the thickness of the framework of the product is relatively low, so that the product has relatively low structural strength and relatively short service life.
For another example, the literature technology (Wang Mengmeng. Preparation and performance research of MgO foamed ceramics. Master academic thesis of Nanjing aerospace university, 2017) uses industrial MgO as raw material, and adds Al 2 O 3 The MgO foamed ceramic is prepared from polyvinyl alcohol, carboxymethyl cellulose and a low-temperature adhesive, but industrial MgO adopted by the technology is a compact raw material, so that the surface of a framework of the filter is compact, the adsorption capacity to nonmetallic inclusions is weak, and the filtering effect needs to be improved.
For another example, in the patent technology of 'a ceramic filter and a preparation method thereof' (201310050569.4), the ceramic filter is prepared by taking materials such as zirconia, silica, alumina, magnesia, mullite, talc, feldspar and the like and biochar as raw materials and taking natural resin or silica sol as a binder, but the material composition adopted by the technology is too complex, and liquid phase is easily generated at high temperature to reduce the strength of the filter; meanwhile, the adopted raw materials are compact materials, so that the surface of the framework of the filter is compact, and the adsorption capacity to nonmetallic inclusions is weak; in addition, although this technique introduces carbon, since carbon belongs to an inert phase in the sintering theory, it is difficult to sinter, so that the interface compatibility between the oxide material and carbon is poor, limiting the strength of the product.
In summary, there are still some technical defects in the prior art regarding magnesium and its alloy melt and molten steel filter: (1) The composition is too complex, so that excessive liquid phase is easily generated in a high-temperature service environment, and the strength of the filter is reduced; (2) The MgO has large thermal expansion coefficient, and the thermal shock stability needs to be improved; (3) The surface of the filter framework is compact, the adsorption capacity to impurities is limited, and the filtering effect is limited; (4) When biochar is used as a raw material, oxides and carbon are difficult to sinter, interface compatibility is poor, and the strength of a product is limited.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and aims to provide a preparation method of a silicon nitride whisker reinforced periclase-spinel-carbon filter, and the silicon nitride whisker reinforced periclase-spinel-carbon filter prepared by the method has high strength, excellent thermal shock stability and excellent filtering effect; the method is suitable for the field of purification of high-quality molten steel and the field of purification of magnesium and magnesium alloy melts.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 320-400 ℃ at the speed of 2-5 ℃/min, preserving the heat for 1-3 h, and cooling to obtain the high-porosity porous fine aluminum oxide powder.
Step 1.2, taking 10-40 wt% of the porous alumina fine powder with high porosity and 60-90 wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 1-3 hours; adding 3-6 wt% of alumina sol of the raw materials, and mixing for 10-20 min to obtain a mixture.
Step 1.3, performing mechanical pressing molding on the mixture under the condition of 100-150 MPa, and drying the molded blank for 24-48 h at the temperature of 110 ℃; then heating to 1600-1750 ℃ at the speed of 4-5 ℃/min, preserving the heat for 2-6 h, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic.
The periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity is 24-32%, and the volume density is 2.42-2.71 g/cm 3 The average pore diameter of the pores is 600-1550 nm.
And step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is less than 30 microns.
Step 2, preparation of modified periclase-spinel ceramic fine powder
And 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 1.5-5.5, and stirring for 10-20 min to obtain a modified solution.
And 2.2, putting the micro-nano-aperture periclase-spinel ceramic fine powder and the modified solution in a mass ratio of 100: 20-36 into a vacuum device, vacuumizing to 2.0-3.0 kPa, adding the modified solution, stirring for 15-30 min, closing a vacuumizing system, and naturally drying for 24-32 h to obtain the modified periclase-spinel ceramic fine powder.
Step 3, preparation of pretreated polyurethane foam
Soaking 8-20 ppi polyurethane foam in NaOH solution for 2-4 h, taking out, washing with deionized water for 2-6 times, and airing to obtain the pretreated polyurethane foam.
Step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 75-85 wt% of modified periclase-spinel ceramic fine powder, 7-11 wt% of magnesia fine powder, 3-7 wt% of modified coal tar asphalt powder, 2.5-5 wt% of simple substance silicon powder and 0.5-3 wt% of sodium carboxymethylcellulose as raw materials, putting the raw materials into a mixer, mixing for 2-5 h, adding 2-5 wt% of alumina sol, 0.04-0.15 wt% of water reducing agent, 0.3-1.3 wt% of defoaming agent and 20-35 wt% of deionized water, and stirring for 40-60 min to obtain the ceramic slurry with thixotropy.
Immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 10-15 min, taking out, removing redundant ceramic slurry by using a roll machine, curing at room temperature for 15-26h, and drying at 80-110 ℃ for 12-24 h; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressures less than 1.0X 10 -6.4 And (3) under the condition of Pa atmosphere, heating to 1200-1300 ℃ at the speed of 0.5-2 ℃/min, preserving the heat for 2-4 h, and cooling to obtain the periclase-spinel-carbon filter pre-sintered body.
Dipping the periclase-spinel-carbon filter pre-sintered body into the ceramic slurry with thixotropy for 10-20 minutes, taking out the body, and treating the body in a centrifuge at a rotating speed of 200-450 r/min for 3-5 minutes to obtain a secondary slurry-coated periclase-spinel-carbon filter blank; naturally drying the secondary slurry-periclase-spinel-carbon filter blank for 20-40 h, drying at 80-110 ℃ for 12-36 h, and then drying in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) under the atmosphere condition of Pa, heating to 1300-1400 ℃ at the speed of 2-6 ℃/min, preserving the heat for 3-6 h, and cooling to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter.
The particle size of the aluminum hydroxide fine powder is less than 44 mu m; al of the aluminum hydroxide fine powder 2 O 3 The content is 64-66 wt%.
The particle size of the light-burned magnesite fine powder is less than 44 mu m; the MgO content of the light-burned magnesite fine powder is more than 95wt%.
1.2, the aluminum sol is the same as the aluminum sol in the step 4; al of the aluminum sol 2 O 3 The content is 20-45 wt%.
Fe (NO) of the iron nitrate nonahydrate 3 ) 3 ·9H 2 The O content is more than 98wt%.
The solvent of the NaOH solution is deionized water; the concentration of the NaOH solution is 6-8 mol/L.
The particle size of the magnesite fine powder is less than 44 mu m; the MgO content of the magnesite fine powder is more than 96wt%.
The particle size of the modified coal tar asphalt powder is less than 74 mu m; the C content of the modified coal tar asphalt powder is more than 70wt%.
The particle size of the elemental silicon powder is less than 45 μm; the Si content of the elemental silicon powder is more than 98wt%.
The water reducing agent is sodium lignosulphonate or polycarboxylate; the lignin content in the sodium lignin sulfonate is 45-60 wt%, and the side chain molecular weight in the polycarboxylate is 700-2300.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following positive effects:
(1) The invention uses the modified periclase-spinel ceramic fine powder as a raw material to form a sawtooth occlusion interface and silicon nitride whiskers with special distribution, thereby obviously improving the strength and the thermal shock stability of the product.
(1) The method directly takes porous alumina fine powder and light-burned magnesite fine powder with high porosity as raw materials, does not need to additionally add pore-forming agents, controls the microstructure of the periclase-spinel ceramic fine powder through alumina sol, special forming pressure and a burning system, and obtains the periclase-spinel ceramic fine powder which can be applied to high-temperature service conditions and has a micro-nano porous structure. The fine powder has a rough surface structure, the contact area between the fine powder/the fine powder and the fine powder/the modified coal tar asphalt powder is increased, the material transmission rate is accelerated in the sintering process, solid-solid neck connection is formed, a sawtooth occlusion-shaped interface is formed among micro-particles, and the product strength is improved.
(2) The invention takes the modified periclase-spinel ceramic fine powder with through air holes as the raw material, has rough surface structure, increases the contact area of the ceramic slurry and the polyurethane foam template, increases the thickness of the framework by utilizing the special secondary slurry hanging process, avoids the product from forming a hollow structure and improves the strength of the product.
(3) According to the invention, the micro-nano porous structure of the modified periclase-spinel ceramic fine powder and the catalyst attached to the interior of the micro-nano porous structure are utilized to promote the in-situ generation of the silicon nitride whiskers in the surface and the internal holes, and the silicon nitride whiskers generated in the matrix in situ form a special net-shaped interweaving structure, so that the strength and the thermal shock stability of the product are further improved. Solves the problems that the existing silicon nitride crystal whisker can only be formed in the matrix gap and has poor interface compatibility.
(4) When the material is subjected to the action of rapid change of environmental temperature in the using process, microcracks are generated at weak positions of the material, the material absorbs destructive stress by utilizing the composite reinforcement of a sawtooth-meshed interface and specially-distributed silicon nitride whiskers, and when the cracks expand and meet the micro-nano holes and the silicon nitride whiskers, the holes and the whiskers can inhibit the accumulation of strain energy and prevent the instantaneous expansion of the cracks, so that the thermal shock stability of the product is improved.
(2) The invention utilizes the special micro-nano porous structure of the periclase-spinel-carbon filter and combines with the carbothermic reduction reaction, thereby improving the adsorption capacity to the impurities and improving the purification effect.
(1) The invention adopts the modified periclase-spinel ceramic fine powder as the raw material, so that the product skeleton has a micro-nano porous structure, the specific surface area of the skeleton is increased, the product skeleton can be fully contacted with molten steel, and the adsorption capacity on impurities is improved.
(2) According to the invention, by combining with a carbothermic reduction reaction, mgO, spinel, C and molten steel are easy to react to form an active magnesium aluminate spinel layer at the interface of a product skeleton and the molten steel, under a high-temperature service condition, the MgO and the C are subjected to the carbothermic reduction reaction to form Mg steam, and the Mg steam enters the molten steel through micro-nano air holes in the product, so that the effect of a strong deoxidizer is achieved, and the total oxygen content of the molten steel is reduced; meanwhile, mg vapor reacts with other inclusions to form larger-size inclusions, so that the inclusions float upwards easily, and the filtering effect is enhanced.
(3) In the high-temperature service process, mgO reacts with C, and formed gases such as CO and the like can escape into molten steel through micro-nano air holes in the framework to form micron-sized bubbles, so that small-size inclusions in the molten steel can be favorably adsorbed, the inclusions in the molten steel are further reduced, and the purification effect of products is improved.
The inventionThe prepared silicon nitride whisker reinforced periclase-spinel-carbon filter is detected as follows: the apparent porosity is 80-90%; the volume density is 0.39-0.71 g/cm 3 (ii) a The compressive strength is 1.5-3.6 MPa; the phase composition mainly comprises periclase, magnesium aluminate spinel, graphite and beta-Si 3 N 4 And a small amount of MgAlON.
Therefore, the silicon nitride whisker reinforced periclase-spinel-carbon filter prepared by the method has high strength, excellent thermal shock stability and excellent filtering effect; the method is suitable for the field of purification of high-quality molten steel and the field of purification of magnesium and magnesium alloy melts.
Detailed Description
The invention is further described with reference to specific embodiments, without limiting its scope.
A silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof. The preparation method of the embodiment comprises the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 320-400 ℃ at the speed of 2-5 ℃/min, preserving the heat for 1-3 h, and cooling to obtain the high-porosity porous fine aluminum oxide powder.
Step 1.2, taking 10-40 wt% of the porous alumina fine powder with high porosity and 60-90 wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 1-3 hours; adding 3-6 wt% of alumina sol of the raw materials, and mixing for 10-20 min to obtain a mixture.
1.3, mechanically pressing the mixture under the condition of 100-150 MPa, and drying a formed blank body for 24-48 h at the temperature of 110 ℃; then heating to 1600-1750 ℃ at the speed of 4-5 ℃/min, preserving the heat for 2-6 h, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic.
The periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity is 24-32%, and the volume density is 2.42-2.71 g/cm 3 The average pore diameter of the pores is 600-1550 nm.
And step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is less than 30 microns.
Step 2, preparation of modified periclase-spinel ceramic fine powder
And 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 1.5-5.5, and stirring for 10-20 min to obtain a modified solution.
And 2.2, putting the micro-nano-aperture periclase-spinel ceramic fine powder and the modified solution in a mass ratio of 100: 20-36 into a vacuum device, vacuumizing to 2.0-3.0 kPa, adding the modified solution, stirring for 15-30 min, closing a vacuumizing system, and naturally drying for 24-32 h to obtain the modified periclase-spinel ceramic fine powder.
Step 3, preparation of pretreated polyurethane foam
Soaking 8-20 ppi polyurethane foam in NaOH solution for 2-4 h, taking out, washing with deionized water for 2-6 times, and airing to obtain the pretreated polyurethane foam.
Step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 75-85 wt% of modified periclase-spinel ceramic fine powder, 7-11 wt% of magnesite fine powder, 3-7 wt% of modified coal tar asphalt powder, 2.5-5 wt% of simple substance silicon powder and 0.5-3 wt% of sodium carboxymethyl cellulose as raw materials, placing the raw materials into a mixer, mixing for 2-5 h, adding 2-5 wt% of alumina sol, 0.04-0.15 wt% of water reducing agent, 0.3-1.3 wt% of defoaming agent and 20-35 wt% of deionized water as the raw materials, and stirring for 40-60 min to obtain the ceramic slurry with thixotropy.
Immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 10-15 min, taking out, removing redundant ceramic slurry by using a roll machine, curing at room temperature for 15-26h, and drying at 80-110 ℃ for 12-24 h; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) under the condition of Pa atmosphere, heating to 1200-1300 ℃ at the speed of 0.5-2 ℃/min, preserving the heat for 2-4 h, and cooling to obtain the periclase-spinel-carbon filter pre-sintered body.
Dipping the periclase-spinel-carbon filter pre-sintered body into the ceramic slurry with thixotropy for 10-20 minutes, taking out the body and then treating the body in a centrifuge at a rotating speed of 200-450 r/min for 3-5 minutes to obtain a secondary slurry-coated periclase-spinel-carbon filter blank body; naturally drying the secondary slurry-periclase-spinel-carbon filter blank for 20-40 h, drying at 80-110 ℃ for 12-36 h, and then drying in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) heating to 1300-1400 ℃ at the speed of 2-6 ℃/min under the atmosphere condition of Pa, preserving the heat for 3-6 h, and cooling to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter.
Al of the aluminum hydroxide fine powder 2 O 3 The content is 64-66 wt%.
The MgO content of the light-burned magnesite fine powder is more than 95wt%.
Al of the aluminum sol 2 O 3 The content is 20-45 wt%.
Fe (NO) of the iron nitrate nonahydrate 3 ) 3 ·9H 2 The O content is more than 98wt%.
The concentration of the NaOH solution is 6-8 mol/L.
The MgO content of the magnesite fine powder is more than 96wt%.
The C content of the modified coal tar asphalt powder is more than 70wt%.
The Si content of the elemental silicon powder is more than 98wt%.
The water reducing agent is sodium lignosulphonate or polycarboxylate; the lignin content in the sodium lignin sulfonate is 45-60 wt%, and the side chain molecular weight in the polycarboxylate is 700-2300.
In this embodiment:
the particle size of the aluminum hydroxide fine powder is less than 44 mu m;
the particle size of the light-burned magnesite fine powder is less than 44 mu m;
the solvent of the NaOH solution is deionized water;
the particle size of the magnesite fine powder is less than 44 mu m;
the particle size of the modified coal tar asphalt powder is less than 74 mu m;
the particle size of the elemental silicon powder is less than 45 μm;
the aluminum sol in the step 1.2 is the same as the aluminum sol in the step 4.
The detailed description is omitted in the embodiments.
Example 1
A silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof. The preparation method of the embodiment comprises the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 320 ℃ at the speed of 2 ℃/min, preserving the heat for 1h, and cooling to obtain the high-porosity porous fine aluminum oxide powder.
Step 1.2, taking 10wt% of the high-porosity porous alumina fine powder and 90wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 1 hour; adding 3wt% of alumina sol of the raw materials, and mixing for 10min to obtain a mixture.
Step 1.3, performing mechanical pressing molding on the mixture under the condition of 100MPa, and drying a molded blank at the temperature of 110 ℃ for 24 hours; and then heating to 1600 ℃ at the speed of 4 ℃/min, preserving the heat for 2h, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic.
The periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity is 24 percent, and the volume density is 2.71g/cm 3 The average pore diameter of the pores was 600nm.
And step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is less than 30 microns.
Step 2, preparation of modified periclase-spinel ceramic fine powder
And 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 1.5, and stirring for 10min to obtain a modified solution.
And 2.2, placing the micro-nano-aperture periclase-spinel ceramic fine powder in a vacuum device according to the mass ratio of the micro-nano-aperture periclase-spinel ceramic fine powder to the modified solution of 100: 20, vacuumizing to 2kPa, adding the modified solution, stirring for 15min, closing a vacuumizing system, and naturally drying for 24h to obtain the modified periclase-spinel ceramic fine powder.
Step 3, preparation of pretreated polyurethane foam
And (3) soaking 8ppi polyurethane foam in NaOH solution for 2h, taking out, washing with deionized water for 2 times, and airing to obtain the pretreated polyurethane foam.
Step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 75wt% of modified periclase-spinel ceramic fine powder, 11wt% of magnesite fine powder, 7wt% of modified coal tar asphalt powder, 4wt% of elemental silicon powder and 3wt% of sodium carboxymethylcellulose as raw materials, putting the raw materials into a mixer, mixing for 2 hours, adding 2wt% of alumina sol, 0.04wt% of water reducing agent, 0.3wt% of defoaming agent and 20wt% of deionized water as the raw materials, and stirring for 40 minutes to obtain ceramic slurry with thixotropy.
Immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 10min, taking out, removing redundant ceramic slurry by using a double-roller machine, curing at room temperature for 15h, and drying at 80 ℃ for 12h; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) under the condition of Pa atmosphere, heating to 1200 ℃ at the speed of 0.5 ℃/min, preserving the heat for 2h, and cooling to obtain the periclase-spinel-carbon filter pre-sintered body.
Impregnating the periclase-spinel-carbon filter pre-sintered body in the toolDipping the ceramic slurry with thixotropy for 10 minutes, taking out the ceramic slurry, and treating the ceramic slurry in a centrifuge at the rotating speed of 200r/min for 3 minutes to obtain a secondary slurry-periclase-spinel-carbon filter blank; naturally drying the secondary slurry periclase-spinel-carbon filter blank for 20h, drying at 80 ℃ for 12h, and then drying in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) heating to 1300 ℃ at the speed of 2 ℃/min under the atmosphere condition of Pa, preserving the heat for 3h, and cooling to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter.
Al of the aluminum hydroxide fine powder 2 O 3 The content was 64.07wt%.
The MgO content of the light-burned magnesite fine powder is 95.3wt%.
Al of the aluminum sol 2 O 3 The content was 20wt%.
Fe (NO) of the iron nitrate nonahydrate 3 ) 3 ·9H 2 The O content was 99.2wt%.
The concentration of the NaOH solution is 6mol/L.
The MgO content of the magnesite fine powder is 96.2wt%.
The C content of the modified coal tar asphalt powder is 71.15wt%.
The Si content of the elemental silicon powder is 98.32wt%.
The water reducing agent is sodium lignosulphonate, and the lignin content in the sodium lignosulphonate is 48wt%.
The silicon nitride whisker reinforced periclase-spinel-carbon filter prepared in this example was tested: the apparent porosity is 90%; the bulk density is 0.39g/cm 3 (ii) a The compressive strength is 1.5MPa; the phase composition mainly comprises periclase, magnesium aluminate spinel, graphite and beta-Si 3 N 4 And a small amount of MgAlON.
Example 2
A silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof. The preparation method of the embodiment comprises the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 350 ℃ at the speed of 3 ℃/min, preserving the heat for 2h, and cooling to obtain the high-porosity porous fine aluminum oxide powder.
Step 1.2, taking 20wt% of the high-porosity porous alumina fine powder and 80wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 2.5 hours; adding 4wt% of alumina sol of the raw materials, and mixing for 14min to obtain a mixture.
Step 1.3, performing mechanical pressing molding on the mixture under the condition of 120MPa, and drying a molded blank at the temperature of 110 ℃ for 30h; and then heating to 1680 ℃ at the speed of 4 ℃/min, preserving the heat for 4h, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic.
The periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity was 26.4%, and the bulk density was 2.64g/cm 3 The average pore diameter of the pores was 860nm.
And step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is less than 30 microns.
Step 2, preparation of modified periclase-spinel ceramic fine powder
And 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 2.8, and stirring for 13min to obtain a modified solution.
And 2.2, placing the micro-nano-aperture periclase-spinel ceramic fine powder in a vacuum device according to the mass ratio of the micro-nano-aperture periclase-spinel ceramic fine powder to the modified solution of 100: 26, vacuumizing to 2.3kPa, adding the modified solution, stirring for 18min, closing a vacuumizing system, and naturally drying for 26h to obtain the modified periclase-spinel ceramic fine powder.
Step 3, preparation of pretreated polyurethane foam
And (2) soaking 12ppi of polyurethane foam in NaOH solution for 3h, taking out, washing with deionized water for 3 times, and airing to obtain the pretreated polyurethane foam.
Step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 78.5wt% of modified periclase-spinel ceramic fine powder, 9.7wt% of magnesite fine powder, 6wt% of modified coal tar asphalt powder, 3.3wt% of simple substance silicon powder and 2.5wt% of sodium carboxymethyl cellulose as raw materials, putting the raw materials into a mixer, mixing for 3 hours, adding 3wt% of alumina sol, 0.08wt% of water reducing agent, 0.6wt% of defoaming agent and 26wt% of deionized water as the raw materials, and stirring for 46 minutes to obtain ceramic slurry with thixotropy.
Immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 12min, taking out, removing redundant ceramic slurry by using a double-roller machine, curing at room temperature for 18h, and drying at 90 ℃ for 17h; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) under the atmosphere condition of Pa, heating to 1230 ℃ at the speed of 1 ℃/min, preserving the heat for 3h, and cooling to obtain the periclase-spinel-carbon filter pre-sintered body.
Dipping the periclase-spinel-carbon filter pre-sintered body into the ceramic slurry with thixotropy for 13 minutes, taking out the body, and then treating the body in a centrifuge at a rotating speed of 270r/min for 4 minutes to obtain a secondary slurry-coated periclase-spinel-carbon filter blank; naturally drying the secondary slurry periclase-spinel-carbon filter blank for 26h, then drying for 20h at the temperature of 90 ℃, and then drying in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) heating to 1330 ℃ at the speed of 3 ℃/min under the atmosphere condition of Pa, preserving the temperature for 4h, and cooling to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter.
Al of the aluminum hydroxide fine powder 2 O 3 The content was 64.79wt%.
The MgO content of the light-burned magnesite fine powder is 95.87wt%.
Al of the aluminum sol 2 O 3 The content was 28wt%.
Fe (NO) of the iron nitrate nonahydrate 3 ) 3 ·9H 2 The O content was 99.4wt%.
The concentration of the NaOH solution is 6.6mol/L.
The MgO content of the magnesite fine powder is 96.6wt%.
The C content of the modified coal tar asphalt powder is 72.47wt%.
The Si content of the elemental silicon powder is 98.91wt%.
The water reducing agent is polycarboxylate, and the molecular weight of a side chain in the polycarboxylate is 1000.
The silicon nitride whisker reinforced periclase-spinel-carbon filter prepared in this example was tested: the apparent porosity is 87%; the bulk density is 0.46g/cm 3 (ii) a The compressive strength is 1.8MPa; the phase composition mainly comprises periclase, magnesium aluminate spinel, graphite and beta-Si 3 N 4 And a small amount of MgAlON.
Example 3
A silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof. The preparation method of the embodiment comprises the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 380 ℃ at the speed of 4 ℃/min, preserving the heat for 2.5h, and cooling to obtain the high-porosity porous alumina fine powder.
Step 1.2, taking 30wt% of the high-porosity porous alumina fine powder and 70wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 2 hours; and adding 5wt% of alumina sol of the raw materials, and mixing for 17min to obtain a mixture.
Step 1.3, performing mechanical pressing molding on the mixture under the condition of 130MPa, and drying the molded blank at the temperature of 110 ℃ for 40h; and then heating to 1710 ℃ at the speed of 5 ℃/min, preserving the heat for 5h, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic.
The periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity was 29.7%, and the bulk density was 2.54g/cm 3 Qi ofThe average pore diameter of the pores is 1270nm.
And step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is less than 30 microns.
Step 2, preparation of modified periclase-spinel ceramic fine powder
And 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 4, and stirring for 17min to obtain a modified solution.
And 2.2, putting the micro-nano-aperture periclase-spinel ceramic fine powder into a vacuum device according to the mass ratio of the micro-nano-aperture periclase-spinel ceramic fine powder to the modified solution of 100: 30, vacuumizing to 2.7kPa, adding the modified solution, stirring for 25min, closing a vacuumizing system, and naturally drying for 29h to obtain the modified periclase-spinel ceramic fine powder.
Step 3, preparation of pretreated polyurethane foam
And (2) soaking 16ppi of polyurethane foam in NaOH solution for 3h, taking out, washing with deionized water for 5 times, and airing to obtain the pretreated polyurethane foam.
Step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 82.3wt% of modified periclase-spinel ceramic fine powder, 8.2wt% of magnesite fine powder, 3wt% of modified coal tar asphalt powder, 5wt% of simple substance silicon powder and 1.5wt% of sodium carboxymethyl cellulose as raw materials, putting the raw materials into a mixer, mixing for 4 hours, adding 4wt% of alumina sol, 0.11wt% of water reducing agent, 0.9wt% of defoaming agent and 28wt% of deionized water as the raw materials, and stirring for 52 minutes to obtain ceramic slurry with thixotropy.
Immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 13min, taking out, removing redundant ceramic slurry by using a roll machine, maintaining for 22h at room temperature, and drying for 20h at 100 ℃; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) heating to 1260 ℃ at the speed of 1.5 ℃/min under the atmosphere condition of Pa, preserving the heat for 3h, and cooling to obtain the periclase-spinel-carbon filter pre-sintered body.
Dipping the periclase-spinel-carbon filter pre-sintered body into the ceramic slurry with thixotropy for 17 minutes, taking out the body, and then treating the body in a centrifuge at the rotating speed of 350r/min for 4 minutes to obtain a secondary slurry-periclase-spinel-carbon filter blank; naturally drying the secondary slurry periclase-spinel-carbon filter blank for 33h, drying at 100 ℃ for 28h, and then drying in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 And (3) under the atmosphere condition of Pa, heating to 1370 ℃ at the speed of 5 ℃/min, preserving heat for 5 hours, and cooling to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter.
Al of the aluminum hydroxide fine powder 2 O 3 The content was 65.14wt%.
The MgO content of the light-burned magnesite fine powder is 96.21wt%.
Al of the aluminum sol 2 O 3 The content was 36wt%.
Fe (NO) of the iron nitrate nonahydrate 3 ) 3 ·9H 2 The O content was 98.5wt%.
The concentration of the NaOH solution is 7.1mol/L.
The MgO content of the magnesite fine powder is 96.9wt%.
The C content of the modified coal tar asphalt powder is 73.26wt%.
The Si content of the elemental silicon powder is 99.06wt%.
The water reducing agent is sodium lignosulphonate, and the lignin content in the sodium lignosulphonate is 58wt%.
The silicon nitride whisker reinforced periclase-spinel-carbon filter prepared in this example was tested: the apparent porosity is 82%; the bulk density is 0.6g/cm 3 (ii) a The compressive strength is 2.7MPa; the phase composition mainly comprises periclase, magnesium aluminate spinel, graphite and beta-Si 3 N 4 And a small amount of MgAlON.
Example 4
A silicon nitride whisker reinforced periclase-spinel-carbon filter and a preparation method thereof. The preparation method of the embodiment comprises the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 400 ℃ at the speed of 5 ℃/min, preserving the heat for 3h, and cooling to obtain the high-porosity porous fine aluminum oxide powder.
Step 1.2, taking 40wt% of the high-porosity porous alumina fine powder and 60wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 3 hours; adding 6wt% of alumina sol of the raw materials, and mixing for 20min to obtain a mixture.
Step 1.3, performing mechanical pressing molding on the mixture under the condition of 150MPa, and drying a molded blank at the temperature of 110 ℃ for 48 hours; and then heating to 1750 ℃ at the speed of 5 ℃/min, preserving the heat for 6 hours, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic.
The periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity is 32 percent, and the volume density is 2.42g/cm 3 The average pore diameter of the pores was 1550nm.
And step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is less than 30 microns.
Step 2, preparation of modified periclase-spinel ceramic fine powder
And 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 5.5, and stirring for 20min to obtain a modified solution.
And 2.2, putting the micro-nano-aperture periclase-spinel ceramic fine powder into a vacuum device according to the mass ratio of the micro-nano-aperture periclase-spinel ceramic fine powder to the modified solution of 100: 36, vacuumizing to 3kPa, adding the modified solution, stirring for 30min, closing a vacuumizing system, and naturally drying for 32h to obtain the modified periclase-spinel ceramic fine powder.
Step 3, preparation of pretreated polyurethane foam
And (2) soaking 20ppi of polyurethane foam into NaOH solution for 4h, taking out, washing with deionized water for 6 times, and airing to obtain the pretreated polyurethane foam.
Step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 85wt% of modified periclase-spinel ceramic fine powder, 7wt% of magnesite fine powder, 5wt% of modified coal tar asphalt powder, 2.5wt% of simple substance silicon powder and 0.5wt% of sodium carboxymethyl cellulose as raw materials, putting the raw materials into a mixer, mixing for 5 hours, adding 5wt% of alumina sol, 0.15wt% of water reducing agent, 1.3wt% of defoaming agent and 35wt% of deionized water, and stirring for 60 minutes to obtain ceramic slurry with thixotropy.
Immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 15min, taking out, removing redundant ceramic slurry by using a roll machine, maintaining for 26h at room temperature, and drying for 24h at 110 ℃; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressures less than 1.0X 10 -6.4 And (3) under the atmosphere condition of Pa, heating to 1300 ℃ at the speed of 2 ℃/min, preserving the heat for 4h, and cooling to obtain the periclase-spinel-carbon filter pre-sintered body.
Dipping the periclase-spinel-carbon filter pre-sintered body into the ceramic slurry with thixotropy for 20 minutes, taking out the body, and then treating the body in a centrifuge at the rotating speed of 450r/min for 5 minutes to obtain a secondary slurry-coated periclase-spinel-carbon filter blank; naturally drying the secondary slurry periclase-spinel-carbon filter blank for 40h, drying at 110 ℃ for 36h, and then carrying out N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 Under the condition of Pa atmosphere, the temperature is raised to 1400 ℃ at the speed of 6 ℃/min, the temperature is kept for 6h, and the silicon nitride crystal whisker reinforced periclase-spinel-A carbon filter.
Al of the aluminum hydroxide fine powder 2 O 3 The content was 65.93wt%.
The MgO content of the light-burned magnesite fine powder is 96.91wt%.
Al of the aluminum sol 2 O 3 The content was 45wt%.
Fe (NO) of the iron nitrate nonahydrate 3 ) 3 ·9H 2 The O content was 98.6wt%.
The concentration of the NaOH solution is 8mol/L.
The MgO content of the magnesite fine powder is 97.1wt%.
The C content of the modified coal tar asphalt powder is 74.12wt%.
The Si content of the elemental silicon powder is 99.52wt%.
The water reducing agent is polycarboxylate, and the molecular weight of a side chain in the polycarboxylate is 2000.
The silicon nitride whisker reinforced periclase-spinel-carbon filter prepared in this example was tested: the apparent porosity is 80%; the bulk density is 0.71g/cm 3 (ii) a The compressive strength is 3.6MPa; the phase composition mainly comprises periclase, magnesium aluminate spinel, graphite and beta-Si 3 N 4 And a small amount of MgAlON.
Compared with the prior art, the specific implementation mode has the following positive effects:
(1) In the specific embodiment, the modified periclase-spinel ceramic fine powder is used as a raw material to form a sawtooth occlusion interface and silicon nitride whiskers with special distribution, so that the strength and the thermal shock stability of the product are obviously improved.
(1) In the specific embodiment, porous alumina fine powder with high porosity and light calcined magnesite fine powder are directly used as raw materials, a pore-forming agent is not required to be additionally added, and the microstructure of the periclase-spinel ceramic fine powder is controlled through alumina sol, special forming pressure and a sintering system, so that the periclase-spinel ceramic fine powder which can be applied to high-temperature service conditions and has a micro-nano porous structure is obtained. The fine powder has a rough surface structure, the contact area between the fine powder/the fine powder and the fine powder/the modified coal tar asphalt powder is increased, the material transmission rate is accelerated in the sintering process, solid-solid neck connection is formed, a sawtooth occlusion-shaped interface is formed among micro-particles, and the product strength is improved.
(2) The specific embodiment takes the modified periclase-spinel ceramic fine powder with through air holes as a raw material, has a rough surface structure, increases the contact area of ceramic slurry and a polyurethane foam template, increases the thickness of a framework by utilizing a special secondary slurry hanging process, avoids the product from forming a hollow structure, and improves the strength of the product.
(3) In the specific embodiment, the micro-nano porous structure of the modified periclase-spinel ceramic fine powder and the catalyst attached inside are utilized to promote the in-situ generation of the silicon nitride whiskers in the surface and the internal holes, and the silicon nitride whiskers generated in situ in the matrix form a special net-shaped interweaving structure, so that the strength of the product and the thermal shock stability are further improved. Solves the problems that the existing silicon nitride crystal whisker can only be formed in the matrix gap and has poor interface compatibility.
(4) When the material is subjected to the action of rapid change of environmental temperature in the using process, microcracks are generated at weak positions of the material, the specific embodiment utilizes a sawtooth-meshed interface and specially-distributed silicon nitride whiskers to perform composite reinforcement to absorb destructive stress, and when the cracks expand and meet the micro-nano holes and the silicon nitride whiskers, the holes and the whiskers can inhibit the accumulation of strain energy and prevent the instantaneous expansion of the cracks, so that the thermal shock stability of the product is improved.
(2) The specific embodiment utilizes the special micro-nano porous structure of the periclase-spinel-carbon filter and combines with the carbothermic reduction reaction, thereby improving the adsorption capacity to the impurities and improving the purification effect.
(1) The specific embodiment adopts the modified periclase-spinel ceramic fine powder as the raw material, so that the product framework has a micro-nano porous structure, the specific surface area of the framework is increased, the product framework can be fully contacted with molten steel, and the adsorption capacity on impurities is improved.
(2) In the specific embodiment, the carbon thermal reduction reaction is combined, mgO, spinel, C and molten steel are easy to react to form an active magnesium aluminate spinel layer at the interface of a product skeleton and the molten steel, under the condition of high-temperature service, the MgO and the C are subjected to the carbon thermal reduction reaction to form Mg steam, and the Mg steam enters the molten steel through micro-nano air holes in the product, so that the effect of a strong deoxidizer is achieved, and the total oxygen content of the molten steel is reduced; meanwhile, mg vapor reacts with other inclusions to form larger-size inclusions, so that the inclusions float upwards easily, and the filtering effect is enhanced.
(3) In the high-temperature service process, mgO reacts with C, and formed gases such as CO and the like can escape into molten steel through micro-nano air holes in the framework to form micron-sized bubbles, so that small-size inclusions in the molten steel can be favorably adsorbed, the inclusions in the molten steel are further reduced, and the purification effect of products is improved.
The silicon nitride whisker reinforced periclase-spinel-carbon filter prepared by the embodiment is detected as follows: the apparent porosity is 80-90%; the volume density is 0.39-0.71 g/cm 3 (ii) a The compressive strength is 1.5-3.6 MPa; the phase composition mainly comprises periclase, magnesium aluminate spinel, graphite and beta-Si 3 N 4 And a small amount of MgAlON.
Therefore, the silicon nitride crystal whisker reinforced periclase-spinel-carbon filter prepared by the embodiment has high strength, excellent thermal shock stability and excellent filtering effect; the method is suitable for the field of purification of high-quality molten steel and the field of purification of magnesium and magnesium alloy melts.
Claims (10)
1. A preparation method of a silicon nitride whisker reinforced periclase-spinel-carbon filter is characterized by comprising the following steps:
step 1, preparation of periclase-spinel ceramic fine powder
Step 1.1, heating the fine aluminum hydroxide powder to 320-400 ℃ at the speed of 2-5 ℃/min, preserving the heat for 1-3 h, and cooling to obtain the fine porous aluminum oxide powder with high porosity;
step 1.2, taking 10-40 wt% of the porous alumina fine powder with high porosity and 60-90 wt% of light-burned magnesite fine powder as raw materials, placing the raw materials in a stirrer, and stirring for 1-3 hours; adding 3-6 wt% of alumina sol of the raw materials, and mixing for 10-20 min to obtain a mixture;
step 1.3, performing mechanical pressing molding on the mixture under the condition of 100-150 MPa, and drying the molded blank for 24-48 h at the temperature of 110 ℃; then heating to 1600-1750 ℃ at the speed of 4-5 ℃/min, preserving the heat for 2-6 h, and cooling to obtain the micro-nano-aperture periclase-spinel ceramic;
the periclase-spinel ceramic with the micro-nano aperture comprises: the apparent porosity is 24-32%, and the volume density is 2.42-2.71 g/cm 3 The average pore diameter of the pores is 600-1550 nm;
step 1.4, crushing and screening the micro-nano-aperture periclase-spinel ceramic to obtain micro-nano-aperture periclase-spinel ceramic fine powder, wherein the particle size of the micro-nano-aperture periclase-spinel ceramic fine powder is smaller than 30 microns;
step 2, preparation of modified periclase-spinel ceramic fine powder
Step 2.1, placing the deionized water and the ferric nitrate nonahydrate into a stirrer according to the mass ratio of the deionized water to the ferric nitrate nonahydrate of 100: 1.5-5.5, and stirring for 10-20 min to obtain a modified solution;
step 2.2, placing the micro-nano-aperture periclase-spinel ceramic fine powder and the modified solution in a vacuum device according to the mass ratio of 100: 20-36, vacuumizing to 2.0-3.0 kPa, adding the modified solution, stirring for 15-30 min, closing a vacuumizing system, and naturally drying for 24-32 h to obtain modified periclase-spinel ceramic fine powder;
step 3, preparation of pretreated polyurethane foam
Soaking 8-20 ppi polyurethane foam in NaOH solution for 2-4 h, taking out, washing with deionized water for 2-6 times, and airing to obtain pretreated polyurethane foam;
step 4, preparation of silicon nitride whisker reinforced periclase-spinel-carbon filter
Taking 75-85 wt% of modified periclase-spinel ceramic fine powder, 7-11 wt% of magnesite fine powder, 3-7 wt% of modified coal tar asphalt powder, 2.5-5 wt% of simple substance silicon powder and 0.5-3 wt% of sodium carboxymethyl cellulose as raw materials, placing the raw materials into a mixer, mixing for 2-5 h, adding 2-5 wt% of alumina sol, 0.04-0.15 wt% of water reducing agent, 0.3-1.3 wt% of defoaming agent and 20-35 wt% of deionized water as the raw materials, and stirring for 40-60 min to obtain ceramic slurry with thixotropy;
immersing the pretreated polyurethane foam into the thixotropic ceramic slurry for 10-15 min, taking out, removing redundant ceramic slurry by using a roll machine, curing at room temperature for 15-26h, and drying at 80-110 ℃ for 12-24 h; then in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 -14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 Heating to 1200-1300 ℃ at the speed of 0.5-2 ℃/min under the atmosphere condition of Pa, preserving the heat for 2-4 h, and cooling to obtain a periclase-spinel-carbon filter pre-sintered body;
dipping the periclase-spinel-carbon filter pre-sintered body into the ceramic slurry with thixotropy for 10-20 minutes, taking out the body, and treating the body in a centrifuge at a rotating speed of 200-450 r/min for 3-5 minutes to obtain a secondary slurry-coated periclase-spinel-carbon filter blank; naturally drying the secondary slurry-periclase-spinel-carbon filter blank for 20-40 h, drying at 80-110 ℃ for 12-36 h, and then drying in N 2 Partial pressure of 1atm, O 2 Partial pressure of less than 1.0X 10 - 14.4 Pa and CO partial pressure less than 1.0X 10 -6.4 Under the atmosphere condition of Pa, heating to 1300-1400 ℃ at the speed of 2-6 ℃/min, preserving the heat for 3-6 h, and cooling to obtain the silicon nitride whisker reinforced periclase-spinel-carbon filter;
the water reducing agent is sodium lignosulphonate or polycarboxylate; the lignin content in the sodium lignin sulfonate is 45-60 wt%, and the side chain molecular weight in the polycarboxylate is 700-2300.
2. The method of making a silicon nitride whisker reinforced periclase-spinel-carbon filter as claimed in claim 1, characterized in that the particle size of the aluminum hydroxide fine powder is less than 44 μm; al of the aluminum hydroxide fine powder 2 O 3 The content is 64-66 wt%.
3. A method of making a silicon nitride whisker reinforced periclase-spinel-carbon filter according to claim 1, characterized in that the particle size of the soft-burned magnesite fines is less than 44 μ ι η; the MgO content of the light-burned magnesite fine powder is more than 95wt%.
4. The method of making a silicon nitride whisker reinforced periclase-spinel-carbon filter according to claim 1, characterized in that the aluminum sol of step 1.2 and the aluminum sol of step 4 are the same; al of the aluminum sol 2 O 3 The content is 20-45 wt%.
5. The method for preparing a silicon nitride whisker reinforced periclase-spinel-carbon filter as claimed in claim 1, wherein the iron nitrate nonahydrate is Fe (NO) 3 ) 3 ·9H 2 The O content is more than 98wt%.
6. The method for making a silicon nitride whisker reinforced periclase-spinel-carbon filter according to claim 1, characterized in that the solvent of the NaOH solution is deionized water; the concentration of the NaOH solution is 6-8 mol/L.
7. The method of making a silicon nitride whisker reinforced periclase-spinel-carbon filter according to claim 1, characterized in that the magnesia fine powder has a particle size of less than 44 μm; the MgO content of the magnesite fine powder is more than 96wt%.
8. The method for preparing a silicon nitride whisker reinforced periclase-spinel-carbon filter according to claim 1, characterized in that the particle size of the modified coal tar pitch powder is less than 74 μm; the C content of the modified coal tar asphalt powder is more than 70wt%.
9. The method for preparing a silicon nitride whisker reinforced periclase-spinel-carbon filter as claimed in claim 1, wherein the particle size of the elemental silicon powder is less than 45 μm; the Si content of the elemental silicon powder is more than 98wt%.
10. A silicon nitride whisker reinforced periclase-spinel-carbon filter, characterized in that the silicon nitride whisker reinforced periclase-spinel-carbon filter is a silicon nitride whisker reinforced periclase-spinel-carbon filter prepared according to the method for the preparation of a silicon nitride whisker reinforced periclase-spinel-carbon filter according to any one of claims 1 to 9.
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