CN105693276B - A kind of silicon carbide filter film layer and its low temperature preparation method - Google Patents
A kind of silicon carbide filter film layer and its low temperature preparation method Download PDFInfo
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- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 120
- 238000002360 preparation method Methods 0.000 title claims abstract description 29
- 239000012528 membrane Substances 0.000 claims abstract description 103
- 238000001914 filtration Methods 0.000 claims abstract description 53
- 239000000463 material Substances 0.000 claims abstract description 48
- 239000011148 porous material Substances 0.000 claims abstract description 21
- 239000002245 particle Substances 0.000 claims abstract description 19
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- 238000001035 drying Methods 0.000 claims abstract description 13
- 230000001590 oxidative effect Effects 0.000 claims abstract description 9
- 239000007921 spray Substances 0.000 claims description 32
- 238000010438 heat treatment Methods 0.000 claims description 25
- 239000002002 slurry Substances 0.000 claims description 22
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- 239000012686 silicon precursor Substances 0.000 claims description 21
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 19
- 239000000654 additive Substances 0.000 claims description 16
- 238000006073 displacement reaction Methods 0.000 claims description 15
- 238000002156 mixing Methods 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 238000013461 design Methods 0.000 claims description 10
- 238000000498 ball milling Methods 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 8
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 5
- 238000005245 sintering Methods 0.000 abstract description 15
- 239000000919 ceramic Substances 0.000 abstract description 11
- 239000003245 coal Substances 0.000 abstract description 10
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- 238000010248 power generation Methods 0.000 abstract description 4
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 abstract description 2
- 239000002253 acid Substances 0.000 abstract description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 2
- 150000001282 organosilanes Chemical class 0.000 abstract 2
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
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- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
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- 229910000077 silane Inorganic materials 0.000 description 2
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
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- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
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- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention belongs to porous ceramic film material field, specially a kind of silicon carbide filter film layer and its low temperature preparation method.The group of silicon carbide filter film layer becomes pure matter SiC, superficial film is combined by the accumulation of fine grained silicon carbide, aperture 20nm~20 μm, film layer porosity have the characteristics that high pass porosity, low pressure drop, intensity are high, thermal shock resistance is good, high using temperature between 40~50%.Membrane layer pulp is prepared using thin silicon-carbide particle, organosilane precursor, pore-creating agent addition agent, film layer is prepared using sprayed surface, after drying, sintering obtains pure matter silicon carbide film layer.The present invention is cracked to form using organosilane precursor in conjunction with phase, sintering temperature is low, pore structure control is easy, prepared film layer can use under oxidizing atmosphere, it can also use under reducing atmosphere, acid and alkali resistance corrosive nature is strong, can be used for the various high and low temperature filtering flow purifications such as coal gasification chemical industry and IGCC, PFBC coal gasification power generation, high-temperature flue gas, vehicle exhaust, Water warfare.
Description
Technical Field
The invention belongs to the field of porous ceramic materials, and particularly relates to a silicon carbide filtering membrane layer and a low-temperature preparation method thereof.
Background
High temperature ceramic filter materials generally work under various harsh environmental conditions, and as high temperature ceramic filter materials for gas purification, it is generally required to have: (1) high mechanical strength, high temperature resistance (300-900 ℃) and excellent medium corrosion resistance; (2) high filtration accuracy and filtration gas velocity and low pressure drop; (3) easy back flushing, stable operation and high filtering efficiency; (4) the high-pressure pulse cold gas back-blowing device has good thermal stability and can bear thermal shock caused by frequent back-blowing of high-pressure pulse cold gas. Meanwhile, according to the requirements of application occasions, the high-temperature ceramic filter has to bear the influence of the change of components influenced by the change of chemical characteristics of the airflow and the influence of vibration when spraying ultrafine dust particles, and has the advantages of high dust removal efficiency, high flow rate and the like. The ceramic material selected should not only have thermal chemical and mechanical stability, but also should have durability and high reliability; high chemical stability of the ceramic material is also required especially under high temperature and high pressure conditions when there is corrosion by gas phase sulfur, alkali, chlorine elements.
The filtration performance, high temperature thermal stability and stability of high temperature ceramic filter materials and the reliability of long-term operation are the key to the design of high temperature ceramic filter materials. The high-temperature ceramic filter material with the multifunctional integration of filtering, desulfurization or denitration is a further development direction of gas purification materials. Among various ceramic filter materials, SiC ceramic has the most development prospect, and compared with oxide ceramic, SiC has the characteristics of high thermal conductivity, low expansion coefficient, good thermal shock resistance and high use temperature (above 1000 ℃), so that the SiC ceramic is a preferred material in the aspect of high-temperature fluid filtration in the industrial fields of automobile exhaust, coal chemical industry, molten metal and the like.
However, most silicon carbide filter materials applied to high-temperature gas filtration at present are oxide-bonded SiC ceramics such as clay and the like, and have the defects of low thermal conductivity, poor thermal shock resistance and difficulty in bearing large thermal load fluctuation; especially in high-temperature coal gasification power generation technologies (such as IGCC and PFBC), because the coal contains sodium silicate and NaCl components, Na2Si2O5 converted after the coal is burnt can seriously corrode oxide and combine with a silicon carbide filter material, so that the filter is damaged and fails, and researches show that the pure SiC ceramic material can not be corroded, and meanwhile, the pure silicon carbide material can be used in high-temperature oxidation and reduction atmospheres, but the technology is few in the aspect of the development of the pure silicon carbide filter material at present, and the obtained product has the defects of low strength, uneven pore size distribution, low filtration efficiency, large filtration pressure drop and difficult back flushing and cleaning of a pore structure, so that the application process of the silicon carbide filter material is limited.
In the using process of the filtering material, the filtering precision is determined by the filtering membrane layer attached to the surface of the filtering material support body, the support body plays a role in strength, the gradient structure formed by the support body and the gradient structure can meet the strength requirement and can also meet the filtering effect, and the filtering membrane layer is generally made to be very thin in consideration of the problem of filtering resistance, so that the filtering membrane layer is required to have high tolerance and high filtering performance. The existing silicon carbide support body filtering material film layer is mostly made of oxide materials such as alumina and mullite, people always expect to prepare a pure silicon carbide film layer for better matching with the silicon carbide support body, but because the silicon carbide is not easy to sinter, the sintering temperature is high (1900-2400 ℃), the good combination of crystal grains in the film layer is difficult to be ensured while the pore structure of the film layer is controlled, and the silicon carbide film layer prepared by the conventional method has low strength, is not resistant to scouring and has short service life. Therefore, a silicon carbide filter membrane layer with high use temperature, resistance to corrosion by various media, high strength, low pressure drop, easy regeneration, reliable preparation method and low cost is expected.
Disclosure of Invention
The invention aims to provide a silicon carbide filtering membrane layer and a low-temperature preparation method thereof, and particularly solves the technical problems that:
the invention aims to solve the technical problems that: the pure silicon carbide filter material is provided, and the material composition is more than 99 wt% of silicon carbide, so that the material can have stronger medium corrosion resistance under various atmosphere conditions.
The invention also aims to solve the technical problems that: the preparation method avoids the defects of the preparation technology of the surface filtering membrane layer of the existing filtering material, and provides the ideal pure silicon carbide porous filtering membrane layer which has controllable pore structure, large porosity, high strength, low pressure drop, easy regeneration and reusability.
The invention also aims to solve the technical problems that: the preparation method of the silicon carbide filtering membrane layer is different from the traditional high-temperature sintering process of silicon carbide, and is suitable for large-scale production, and the preparation method has the advantages of easily obtained raw materials, easiness in molding, low sintering temperature, high yield and easier regulation and control of the pore structure of the membrane layer.
In order to solve the technical problem existing in the preparation of the silicon carbide filter membrane layer, the invention adopts the technical scheme that:
the silicon carbide filter membrane layer is composed of pure SiC, the surface membrane layer is formed by stacking and combining fine-particle silicon carbide, the pore diameter is 20 nm-20 mu m, and the porosity of the membrane layer is 40-50%.
The silicon carbide filter membrane layer has a pure SiC content of more than 99 wt% and is formed by cracking an organic silicon precursor, namely silicon carbide and combining original silicon carbide particles through self-sintering.
The preparation method of the silicon carbide filter membrane layer comprises the steps of preparing membrane layer slurry by adopting fine silicon carbide particles, an organic silicon precursor, a pore-forming agent additive and an organic solvent, preparing a membrane layer by adopting a spraying surface, drying and sintering to obtain the silicon carbide membrane layer.
The preparation method of the silicon carbide filter membrane layer comprises the following specific steps:
(1) film layer slurry preparation
Fine silicon carbide particles, an organic silicon precursor, a pore-forming agent additive and an organic solvent are mixed according to the mass percentage of (6-4): (5-3)): (2-1): (8-6) blending, mechanically stirring and then ball-milling to obtain film slurry;
(2) surface film coating
The surface film layer is sprayed by a spraying method which comprises the following steps: spraying the film layer slurry obtained in the step (1) on a rotating prefabricated support body by using a gas spray gun, controlling the film layer thickness by adjusting the relative displacement speed between the support body and the spray gun, drying to obtain a surface film layer, keeping the temperature for 0.5-1.5 hours at the drying temperature of 60-80 ℃, and then continuously heating to 180-220 ℃ for keeping the temperature for 1.5-2.5 hours;
(3) sintering
Sintering the filter material support body coated with the surface film layer in a protective atmosphere of vacuum, argon or other inert gases at a heating rate of 1-3 ℃/min, heating to 600-800 ℃, and preserving heat for 0.5-1 hour to basically crack the organic silicon precursor; the post-heating rate is 5-15 ℃/min, and the temperature is as follows: keeping the temperature at 1100-1600 ℃ for 0.5-5 hours to obtain a silicon carbide filter membrane layer;
(4) and (4) carrying out oxidation treatment on the silicon carbide film layer obtained in the step (3) for 0.5-1.5 hours at the temperature of 750-850 ℃ in an air atmosphere, and removing the pore-forming additive to improve the porosity of the film layer to the design level.
In the preparation method of the silicon carbide filter membrane layer, in the step (1), the granularity of fine silicon carbide particles is between 20nm and 40 mu m, and an organic silicon precursor is polymethyl silane; the pore-forming additive is carbon powder with the granularity of 20 nm-10 mu m; the organic solvent is toluene or xylene.
The preparation method of the silicon carbide filter membrane layer comprises the following steps of (2): spraying the slurry on a rotating prefabricated support body by using a gas spray gun, wherein the flow rate of the slurry of a film layer of the spray gun is 10-20 g/s, the rotation speed is 5-30 rpm/min, the thickness of the film layer is controlled by adjusting the relative displacement speed between the support body and the spray gun to be 50-100 mm/min, and the surface film layer is obtained after drying.
In the preparation method of the silicon carbide filter membrane layer, in the step (3), the thickness of the pure silicon carbide membrane layer is controlled to be 50-1000 microns through the control of the spraying process.
The invention has the following advantages and outstanding effects:
1. the silicon carbide filtering membrane layer provided by the invention is composed of single silicon carbide, so that the corrosion resistance of the material under various high-temperature media is ensured, the stability is good especially under the reducing atmosphere and high-alkali corrosion environment which are not suitable for the oxide membrane layer filtering material, and the long service life of the material is ensured.
2. The silicon carbide filtering membrane layer has a fine pore structure, ensures that the material has good filtering precision and filtering efficiency, is beneficial to realizing back flushing cleaning, is easy to regenerate and can be repeatedly used.
3. The silicon carbide filter membrane layer grain combination mode of the invention is that secondary silicon carbide is combined with primary silicon carbide grains, the consistency of the properties of the two ensures firm combination between grains, and ensures that the material has high strength and thermal shock resistance.
4. The preparation method of the silicon carbide filtering membrane layer has the advantages that the process sintering temperature is far lower than that of the traditional silicon carbide, the pore structure is easy to control finely, the preparation cost is low, products with different specifications can be designed according to needs, the production period is short, the cost is low, the realization is easy, and the product performance can be guaranteed.
5. The silicon carbide filtering membrane layer material provided by the invention has wide application field, can be used for a long time in the atmosphere of oxidation, reduction, high chlorine, alkali, sulfur, silicon and the like, can be used at a high temperature of 1000 ℃, can be used for filtering various industrial flue gases such as crude gas in coal chemical industry and high-temperature coal gasification power generation technology, high-temperature boilers and the like, and can also be used for filtering sewage.
In a word, the silicon carbide filter membrane layer is made of pure silicon carbide, no oxide and other binding phases exist, the silicon carbide filter membrane layer has the characteristics of high porosity, low pressure drop, high strength, good thermal shock resistance and high use temperature, the preparation method is easy to realize, and the product performance can be ensured.
Drawings
FIG. 1: and (3) a surface topography of the silicon carbide filter membrane.
FIG. 2: an enlarged view of the surface of the silicon carbide filter membrane layer.
FIG. 3: and (3) a port topography of the silicon carbide filter membrane layer.
FIG. 4: and (3) bonding the interface of the silicon carbide filter membrane layer and the support body.
Detailed Description
In a specific embodiment, the silicon carbide filtering membrane layer and the low-temperature preparation method thereof comprise the following raw material components in parts by mass:
| fine silicon carbide particles (20 nm-40 μm) | 6～4 |
| Organosilicon precursor (polymethylsilane) | 5～3 |
| Pore-forming agent additive (carbon powder, 20 nm-10 mu m) | 2～1 |
| Organic solvent (toluene or xylene) | 8～6 |
In the raw materials of the silicon carbide filter membrane layer, an organic silicon precursor is cracked and converted into silicon carbide and a small amount of silicon oxide in the sintering process, the generated silicon carbide combines original silicon carbide particles to provide strength guarantee for the membrane layer, the small amount of silicon oxide reacts with carbon powder in the raw materials to form the silicon carbide, the existence of impurity phases is avoided, and pore-forming additives are removed in the subsequent oxidation process, so that the porosity of the membrane layer can be obviously improved, and the silicon carbide is formed. The purified silicon carbide film layer plays an important role in improving the strength, thermal shock resistance, high-temperature stability and long service life of the material.
In the preparation of the material, different raw material compositions and particle size selection can ensure that the silicon carbide filtering membrane layer has high porosity and reasonable pore structure, ensure that the material has good permeability and low filtering pressure, and simultaneously ensure that the fine membrane layer design can well ensure the filtering precision.
The preparation method of the pure silicon carbide filter membrane layer adopts fine silicon carbide particles, an organic silicon precursor, a pore-forming agent additive and an organic solvent to prepare membrane layer raw materials, adopts a rotary spraying method to prepare the filter membrane layer on the surface of a filter material support body, and removes the pore-forming agent through sintering and oxidation after drying to obtain the pure silicon carbide filter membrane layer, and mainly comprises the following steps:
(1) film layer slurry preparation
Fine silicon carbide particles, an organic silicon precursor, a pore-forming agent additive and an organic solvent are mixed according to the mass percentage of (6-4): (5-3): (2-1): (8-6) blending and stirring, and performing ball milling to obtain film layer slurry, wherein the ball milling time is 1-2 hours for later use.
The granularity of the silicon carbide is between 20nm and 40 mu m, the pore-forming additive (carbon powder) is between 20nm and 10 mu m, and the organic silicon precursor is polymethyl silane; the organic solvent is toluene or xylene.
(2) Surface film layer coating preparation
The surface film layer is carried out by adopting a rotary spraying method, and the spraying method comprises the following steps: and (2) spraying the film layer slurry obtained in the step (1) on a rotating filter material support body by using a gas spray gun, wherein the flow rate of the film layer slurry of the spray gun is 10-20 g/s, the rotating speed is 5-30 rpm/min, the film layer thickness is controlled by adjusting the relative displacement speed (50-100 mm/min) between the support body and the spray gun, and drying to obtain the surface film layer. And controlling the thickness of the surface film layer to be 50-1000 mu m by measuring the outer diameter of the dried film tube.
(3) Sintering
And (3) after the film layer is dried at the temperature of between 180 and 220 ℃ for 1.5 to 2.5 hours at the temperature of between 60 and 80 ℃ for 0.5 to 1.5 hours, sintering the filter material support body coated with the surface film layer in the protective atmosphere of vacuum, argon or other inert gases: the initial heating rate is 1-3 ℃/min, the temperature is increased to 600-800 ℃, and the temperature is kept for 0.5-1 hour, so that the organic silicon precursor is basically cracked; and then continuously heating at the heating rate of 5-15 ℃/min and the temperature of 1100-1600 ℃, and preserving the heat for 0.5-5 hours to obtain the silicon carbide filter membrane layer. Wherein,
the film layer is dried at different temperatures in two stages, and has the characteristics and effects that: the low temperature section slowly volatilizes the organic solvent and removes the organic solvent, thereby avoiding the generation of bubbles and holes in the organic solvent due to violent vaporization; the high-temperature section is an organic silicon precursor non-melting treatment stage, so that the generation of the high-temperature flowing phenomenon of the organic silicon precursor can be well avoided, and the uniform distribution of the organic silicon precursor is ensured.
The film layer is sintered at two stages and different temperatures, and has the characteristics and effects that: the low-temperature area is an organic silicon precursor cracking stage, the cracking speed is too high, a large amount of gas is easy to release, the film layer is cracked, the cracking rate can be well controlled by adopting the slow heating rate, and the defects are avoided; after the organosilicon precursor is slowly cracked, the organosilicon precursor enters a silicon carbide grain inoculation and growth stage, the temperature rise speed can be accelerated, and the preparation efficiency can be improved.
(4) And (3) oxidizing the silicon carbide filter membrane layer for 0.5-1.5 hours at the temperature of 750-850 ℃ in an air atmosphere, and removing the pore-forming additive to improve the porosity of the membrane layer to the design level.
In the invention, the average pore diameter of the silicon carbide filter membrane layer is between 20nm and 20 mu m, and the porosity is between 40 and 50 percent. In the pure silicon carbide filter membrane layer, the content of pure SiC is more than 99 wt%, the balance is impurity elements, the grain combination in the material is completely formed by combining silicon carbide particles, and no clay or other oxide combination phases exist.
Hereinafter, the present invention will be described in further detail by way of examples.
Example 1
20nm silicon carbide particles, polymethyl silicane, 20nm carbon powder and dimethylbenzene according to the mass ratio of 4: 5: 2: 8, blending, mechanically stirring and then ball-milling for 1.5 hours to obtain the film layer slurry.
And spraying the slurry on a rotating filter material support body by using a gas spray gun, controlling the thickness of the membrane layer by adjusting the relative displacement speed between the support body and the spray gun, and drying to obtain the surface membrane layer. The material flow rate of the spray gun is 10 g/s, and the rotating speed of the filtering support pipe is 10 rpm/min. The relative displacement speed of the support body and the spray gun is 70mm/min, after spraying, the film layer is dried at 70 ℃ for 1 hour, then is continuously heated to 200 ℃ for 2 hours, and is sintered in vacuum, the initial heating rate is 1 ℃/minute, the temperature is raised to 600 ℃, and the temperature is maintained for 0.5 hour, so that the organic silicon precursor is basically cracked; and then, continuously heating at the heating rate of 5 ℃/min and the temperature of 1100 ℃ for 2 hours to obtain the silicon carbide filter membrane layer.
And then, oxidizing the silicon carbide filter membrane layer for 1 hour at 800 ℃ in the air atmosphere, and removing the pore-forming additive to improve the porosity of the membrane layer to the design level.
Thus, the thickness of the obtained silicon carbide filter membrane layer is 400 μm, the average pore size is 20nm, the porosity is 45%, and the membrane layer can resist the temperature of 1000 ℃.
Example 2
Mixing 40-micron silicon carbide particles, polymethylsilane, 20-micron carbon powder and toluene according to the mass ratio of 5: 3: 1: 6, blending, mechanically stirring and ball-milling for 1 hour to obtain the film slurry.
And spraying the slurry on a rotating filter material support body by using a gas spray gun, controlling the thickness of the membrane layer by adjusting the relative displacement speed between the support body and the spray gun, and drying to obtain the surface membrane layer. The material flow rate of the spray gun is 20 g/s, and the rotating speed of the filtering support pipe is 30 rpm/min. The relative displacement speed of the support body and the spray gun is 50mm/min, after spraying, the film layer is dried at 70 ℃ for 1 hour, then is continuously heated to 200 ℃ for 2 hours, the dried film layer is sintered under vacuum, the initial heating rate is 3 ℃/minute, the temperature is heated to 800 ℃, and the heat is preserved for 1 hour to ensure that the organic silicon precursor is basically cracked; and then, continuously heating at the heating rate of 10 ℃/min and the temperature of 1400 ℃, and preserving the heat for 2 hours to obtain the silicon carbide filter membrane layer.
And then, oxidizing the silicon carbide filter membrane layer for 1 hour at 800 ℃ in the air atmosphere, and removing the pore-forming additive to improve the porosity of the membrane layer to the design level.
Thus, the thickness of the obtained silicon carbide filtering membrane layer is 1000 microns, the average pore size is 20 microns, the porosity is 42%, and the membrane layer can resist the temperature of 1000 ℃.
Example 3
Mixing 10 mu m silicon carbide particles, polymethyl silicane, 500nm carbon powder and toluene according to the mass ratio of 5.5: 4: 2: 7, blending, mechanically stirring and ball-milling for 1 hour to obtain the film slurry.
And spraying the slurry on a rotating filter material support body by using a gas spray gun, controlling the thickness of the membrane layer by adjusting the relative displacement speed between the support body and the spray gun, and drying to obtain the surface membrane layer. The material flow rate of the spray gun is 10 g/s, and the rotating speed of the filtering support pipe is 10 rpm/min. The relative displacement speed of the support body and the spray gun is 5mm/min, after spraying, the film layer is subjected to 70 ℃ and 1 hour, then is continuously heated to 200 ℃ and is dried for 2 hours, the dried film layer is sintered under vacuum, the initial heating rate is 2 ℃/minute, the temperature is raised to 800 ℃, and the heat is preserved for 0.5 hour to ensure that the organic silicon precursor is basically cracked; and then, continuously heating at the heating rate of 15 ℃/min and the temperature of 1600 ℃ for 5 hours to obtain the silicon carbide filter membrane layer.
And then, oxidizing the silicon carbide filter membrane layer for 1 hour at 800 ℃ in the air atmosphere, and removing the pore-forming additive to improve the porosity of the membrane layer to the design level.
Thus, the thickness of the obtained silicon carbide filtering membrane layer is 1000 microns, the average pore size is 500nm, the porosity is 50%, and the membrane layer can resist the temperature of 1000 ℃.
As shown in FIG. 1, it can be seen from the surface topography of the film layer that the film surface prepared by the invention has high flatness and uniform pore structure.
As shown in FIG. 2, it can be seen from the enlargement of the surface of the membrane layer that the pores in the membrane layer are uniformly distributed and the pore diameter is highly uniform, thus ensuring the membrane layer to have higher filtration precision.
As shown in fig. 3, it can be seen from the port morphology of the film layer that the original silicon carbide particles inside the film layer are coated and bonded together by the silicon carbide generated by cracking the organosilicon precursor, thereby ensuring that the film layer has higher strength.
As shown in fig. 4, it can be seen from the interface between the film layer and the support body that the film layer and the support body interface are firmly combined, the film layer is not easy to fall off, and the service life of the film layer can be ensured.
The embodiment result shows that the silicon carbide filtering membrane layer comprises 99% of silicon carbide, does not contain bonding phases such as oxides and the like, has the characteristics of high porosity, low pressure drop, high strength, good thermal shock resistance and high use temperature, is easy to realize, and can ensure the product performance. The invention adopts the organic silicon Precursor (PMS) to generate the binding phase by cracking, the sintering temperature is low, the pore structure is easy to control, the prepared film layer can be used in the oxidizing atmosphere and the reducing atmosphere, the acid and alkali corrosion resistance is strong, and the invention can be used for filtering and purifying various high and low temperature fluids such as coal gasification chemical industry, IGCC and PFBC coal gasification power generation, high temperature flue gas, automobile tail gas, water purification and the like.
Claims (3)
1. A preparation method of a silicon carbide filter membrane layer is characterized by comprising the following specific steps:
20nm silicon carbide particles, polymethyl silicane, 20nm carbon powder and dimethylbenzene according to the mass ratio of 4: 5: 2: 8, blending, mechanically stirring and then ball-milling for 1.5 hours to obtain film slurry;
spraying the slurry on a rotating filter material support body by using a gas spray gun, controlling the thickness of the membrane layer by adjusting the relative displacement speed between the support body and the spray gun, and drying to obtain a surface membrane layer; the material flow rate of the spray gun is 10 g/s, and the rotating speed of the filtering support tube is 10 rpm/min; the relative displacement speed of the support body and the spray gun is 70mm/min, after spraying, the film layer is dried at 70 ℃ for 1 hour, then is continuously heated to 200 ℃ for 2 hours, and is sintered in vacuum, the initial heating rate is 1 ℃/minute, the temperature is raised to 600 ℃, and the temperature is maintained for 0.5 hour, so that the organic silicon precursor is basically cracked; then continuing to heat up at the heating rate of 5 ℃/min and the temperature of 1100 ℃ for 2 hours to obtain a silicon carbide filter membrane layer;
oxidizing the silicon carbide filter membrane layer for 1 hour at 800 ℃ in an air atmosphere, and removing pore-forming additives to improve the porosity of the membrane layer to a design level;
thus, the thickness of the obtained silicon carbide filter membrane layer is 400 μm, the average pore size is 20nm, the porosity is 45%, and the membrane layer can resist the temperature of 1000 ℃.
2. A preparation method of a silicon carbide filter membrane layer is characterized by comprising the following specific steps:
mixing 40-micron silicon carbide particles, polymethylsilane, 20-micron carbon powder and toluene according to the mass ratio of 5: 3: 1: 6, blending, mechanically stirring and then ball-milling for 1 hour to obtain film slurry;
spraying the slurry on a rotating filter material support body by using a gas spray gun, controlling the thickness of the membrane layer by adjusting the relative displacement speed between the support body and the spray gun, and drying to obtain a surface membrane layer; the material flow rate of the spray gun is 20 g/s, and the rotating speed of the filtering support tube is 30 rpm/min; the relative displacement speed of the support body and the spray gun is 50mm/min, after spraying, the film layer is dried at 70 ℃ for 1 hour, then is continuously heated to 200 ℃ for 2 hours, the dried film layer is sintered under vacuum, the initial heating rate is 3 ℃/minute, the temperature is heated to 800 ℃, and the heat is preserved for 1 hour to ensure that the organic silicon precursor is basically cracked; then, continuously heating at the heating rate of 10 ℃/min and the temperature of 1400 ℃, and preserving heat for 2 hours to obtain a silicon carbide filter membrane layer;
oxidizing the silicon carbide filter membrane layer for 1 hour at 800 ℃ in an air atmosphere, and removing pore-forming additives to improve the porosity of the membrane layer to a design level;
thus, the thickness of the obtained silicon carbide filtering membrane layer is 1000 microns, the average pore size is 20 microns, the porosity is 42%, and the membrane layer can resist the temperature of 1000 ℃.
3. A preparation method of a silicon carbide filter membrane layer is characterized by comprising the following specific steps:
mixing 10 mu m silicon carbide particles, polymethyl silicane, 500nm carbon powder and toluene according to the mass ratio of 5.5: 4: 2: 7, blending, mechanically stirring and then ball-milling for 1 hour to obtain film slurry;
spraying the slurry on a rotating filter material support body by using a gas spray gun, controlling the thickness of the membrane layer by adjusting the relative displacement speed between the support body and the spray gun, and drying to obtain a surface membrane layer; the material flow rate of the spray gun is 10 g/s, and the rotating speed of the filtering support tube is 10 rpm/min; the relative displacement speed of the support body and the spray gun is 5mm/min, after spraying, the film layer is subjected to 70 ℃ and 1 hour, then is continuously heated to 200 ℃ and is dried for 2 hours, the dried film layer is sintered under vacuum, the initial heating rate is 2 ℃/minute, the temperature is raised to 800 ℃, and the heat is preserved for 0.5 hour to ensure that the organic silicon precursor is basically cracked; then, continuously heating at the heating rate of 15 ℃/min and the temperature of 1600 ℃ for 5 hours to obtain a silicon carbide filter membrane layer;
oxidizing the silicon carbide filter membrane layer for 1 hour at 800 ℃ in an air atmosphere, and removing pore-forming additives to improve the porosity of the membrane layer to a design level;
thus, the thickness of the obtained silicon carbide filtering membrane layer is 1000 microns, the average pore size is 500nm, the porosity is 50%, and the membrane layer can resist the temperature of 1000 ℃.
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