CN113105269B - Pore filler for ceramic heat transfer element, method for filling pores in ceramic heat transfer element, and ceramic heat transfer element - Google Patents

Pore filler for ceramic heat transfer element, method for filling pores in ceramic heat transfer element, and ceramic heat transfer element Download PDF

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CN113105269B
CN113105269B CN202110494518.5A CN202110494518A CN113105269B CN 113105269 B CN113105269 B CN 113105269B CN 202110494518 A CN202110494518 A CN 202110494518A CN 113105269 B CN113105269 B CN 113105269B
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heat transfer
transfer element
filler
ceramic heat
ceramic
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CN113105269A (en
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高晓红
孙志钦
孟庆凯
李玖重
郜建松
牛凤宾
周天宇
张婧帆
高跃成
段彦明
王恒博
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China Petroleum and Chemical Corp
Sinopec Engineering Group Co Ltd
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Sinopec Engineering Group Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
    • C04B41/81—Coating or impregnation
    • C04B41/85—Coating or impregnation with inorganic materials
    • C04B41/87—Ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
    • C04B41/5001—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with carbon or carbonisable materials
    • C—CHEMISTRY; METALLURGY
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    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
    • C04B41/5076—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with masses bonded by inorganic cements
    • C04B41/5089—Silica sols, alkyl, ammonium or alkali metal silicate cements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/04—Constructions of heat-exchange apparatus characterised by the selection of particular materials of ceramic; of concrete; of natural stone

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Abstract

The invention discloses a ceramic heat transfer element pore filler, a filling method of ceramic heat transfer element pores and a ceramic heat transfer element. The binding agent has the effects that the filling agent can be firmly bound with the ceramic body, the suspending agent has the effects of preventing the solid filling agent from settling due to high density, the dispersing agent has the effects of preventing the filling agent from agglomerating, finally enabling the filling agent to be uniformly dispersed and fully and uniformly mixed with the binding agent, and the filling agent has the effects of improving the thermal conductivity of the filling agent and enhancing the mechanical strength of the ceramic body. The pore filler of the ceramic heat transfer element can be used for completely filling pores and crack defects of the ceramic heat transfer element, avoiding the occurrence of medium mixing and improving the heat conductivity and structural strength of the ceramic heat transfer element.

Description

Pore filler for ceramic heat transfer element, method for filling pores in ceramic heat transfer element, and ceramic heat transfer element
Technical Field
The invention relates to the technical field of ceramics, in particular to a pore filler of a ceramic heat transfer element, a pore filling method of the ceramic heat transfer element and the ceramic heat transfer element.
Background
When a heating furnace in the petrochemical industry recovers the waste heat of low-temperature flue gas, the air preheater manufactured by metal materials generally has the problem of dew point corrosion. In order to prevent low-temperature dew point corrosion, the heat transfer element structural ceramic is made of a non-metallic structural ceramic material, which belongs to an inorganic non-metallic material, and the chemical component of the non-metallic structural ceramic material is acidic oxide SiO 2 Mainly, except hydrofluoric acid and high-temperature phosphoric acid, the material is resistant to corrosion of all inorganic acids, has a structural ceramic material, good chemical stability, high hardness, high temperature resistance and wear resistance, and is suitable for being used as a heat transfer element of an air preheater. However, after the green body of the structural ceramic heat exchange element is sintered and molded, a large number of defects of open pores, closed pores and straight through pores exist generally, and particularly, the defects of the straight through pores exist, so that the problems of medium mixing, leakage and the like of the heat transfer element occur, and the application of the heat exchanger is seriously influenced. The materials for filling ceramic pores and crack defects are mainly two types: one type of filling material is ceramic glaze, which improves the properties of the ceramic surface by applying glaze to the surface of the ceramic and reduces the number of through pores in the ceramic. The disadvantages of such a filling material are: the thermal conductivity of the ceramic glaze is low, and the heat transfer capacity of the ceramic heat exchanger is reduced due to glazing; the ceramic glaze can not fill the internal pores of the ceramic heat transfer element, because the pressure of the internal pores of the ceramic rises when the ceramic heat transfer element is sintered and molded, and the glaze can not completely fill the pores of the ceramic, so that the defects of the internal pores of the ceramic still exist after sintering, and because the thermal conductivity of gas is far lower than that of solid, the thermal conductivity of the ceramic is further reduced. The second filling material is a filling agent and a burning promoter, namely, the pore filling agent and the burning promoter are directly added into the ceramic raw material to make up the pores among the ceramic particles, and the sintering promotion method is adopted to improve the sintering compactness of the material and achieve the purpose of improving the strength of the material. However, the pore filler and the burning promoter can not completely avoid the defects of pores, cracks and the like in the ceramic product, and the ceramic product which can not be penetrated and mixed is difficult to manufactureA ceramic heat transfer element.
Patent CN201710273347.7 describes a refractory material of vanadium pentoxide combined with silicon carbide. Comprises 80-120 parts of high-purity silicon carbide powder, 0.2-2 parts of vanadium pentoxide powder and 1-5 parts of aluminum-silicon alloy powder. The invention also discloses a preparation method of the vanadium pentoxide and silicon carbide combined refractory material. The vanadium pentoxide is used as a pore filling agent and a sintering accelerant, and can fill up pores among silicon carbide particles in the sintering process, and can also play a role in promoting the sintering process, improve the sintering compactness of the material and achieve the purpose of improving the strength of the material. The aluminum-silicon alloy powder is an antioxidant, and the aluminum-silicon alloy can react with an aerobic atmosphere in preference to silicon carbide in the firing process to form a compact structure, so that the oxidation resistance and the mechanical property are improved. The invention can improve the sintering compactness of the material and fill up the pores among the silicon carbide particles, but can not ensure that the pore defects in the silicon carbide ceramic product can be completely avoided, and for a ceramic heat transfer element, the cross mixing of heat exchange media can not be avoided.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The present invention is directed to overcome the above-mentioned drawbacks of the prior art and to provide a pore filler for a ceramic heat transfer element, a method for filling pores in a ceramic heat transfer element, and a ceramic heat transfer element.
The invention is realized by the following steps:
the invention provides a ceramic heat transfer element pore filler which comprises the following components in parts by mass: 40-60 parts of binder, 5-12 parts of suspending agent, 5-12 parts of dispersant and 16-50 parts of filler.
The invention also provides a preparation method of the ceramic heat transfer element pore filler, which comprises the following steps: and mixing the binder, the suspending agent, the dispersing agent and the filler, heating and stirring until a uniform mixed solution is formed, and thus obtaining the ceramic heat transfer element pore filler.
The invention also provides a method for filling the pores of the ceramic heat transfer element, which comprises the following steps: and (3) vacuum impregnating the ceramic heat transfer element in the ceramic heat transfer element pore filler under the vacuum condition, and then heating and curing the ceramic heat transfer element with the ceramic heat transfer element pore filler filled in pores.
The invention also provides a ceramic heat transfer element which is obtained by filling the pores by adopting the filling method.
The invention has the following beneficial effects:
the invention provides a ceramic heat transfer element pore filler, a filling method of ceramic heat transfer element pores and a ceramic heat transfer element. The binder is used for firmly bonding the filler and the ceramic body together, the suspending agent is used for preventing the solid filler from settling due to high density, and the dispersant is used for preventing the filler from agglomerating, so that the filler is uniformly dispersed and the binder is fully and uniformly mixed. The filler has the effects of improving the thermal conductivity of the filler and enhancing the mechanical strength of the ceramic body, the ceramic heat transfer element pore filler can completely fill pores and crack defects of the ceramic heat transfer element, the occurrence of medium mixing is avoided, the thermal conductivity and the structural strength of the ceramic heat transfer element can be improved, the ceramic heat transfer element is subjected to vacuum infiltration in the ceramic heat transfer element pore filler under the vacuum condition, then the ceramic heat transfer element filled with the pore filler in pores is subjected to temperature rise and solidification, and the obtained ceramic heat transfer element has no internal pore defects and surface crack defects and has high thermal conductivity and compressive strength.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Aiming at the problems that the heat conductivity of the ceramic heat exchange element is reduced due to the fact that the existing structural ceramic heat exchange element has through air holes, cracks and the like, and a ceramic glaze air hole filler cannot completely fill the air holes and cracks of the ceramic heat exchange element, the embodiment of the invention provides a filler for filling the through air holes and cracks of the ceramic heat exchange element by a vacuum infiltration method, and relates to a filler for resisting the defects of the air holes, cracks and the like of the structural ceramic heat exchange element.
The pore filler of the ceramic heat transfer element provided by the embodiment of the invention is further improved aiming at the filler which is applied by the inventor and consists of the binder and the filler, and the defect of the ceramic heat transfer element is not ideal because the binder and the filler are difficult to construct and have uneven filling effect.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
in a first aspect, embodiments of the present invention provide a pore filler for a ceramic heat transfer element, where the pore filler mainly comprises a binder, a suspending agent, a dispersant, a filler, and the like. Wherein, the binder includes: water glass, silicone, phenolic resin, furan resin, and the like. The suspending agent mainly comprises: polyvinyl chloride, polystyrene, and the like. The dispersing agent is polytetrafluoroethylene emulsion and the like. The filler has good thermal conductivity besides acid corrosion resistance, and graphite micropowder, silicon carbide micropowder, mullite micropowder and the like are generally selected as fillers of the filler. Wherein the graphite is an artificial graphite material, and the silicon carbide is alpha-silicon carbide micro powder. The binder, the suspending agent, the dispersant and the filler all have acid corrosion resistance.
The embodiment of the invention provides a ceramic heat transfer element pore filler which is a multi-element impregnation filler, wherein the binder has the function of firmly bonding the filler and a ceramic body together, the suspending agent has the function of preventing solid filler from settling due to higher density, the dispersing agent has the function of preventing the filler from agglomerating, and finally the filler is uniformly dispersed and fully and uniformly mixed with the binder, and the filler has the function of improving the thermal conductivity of the filler and enhancing the mechanical strength of the ceramic body. Specifically, the method comprises the following steps:
the binder in the pore filler of the ceramic heat transfer element provided by the embodiment of the invention comprises: water glass, silicone, phenolic resin, furan resin, and the like. The binders of the conventional multi-element ceramic filler are mainly: water glass, phenolic resin, organic silicon, methyl cellulose, furan resin, epoxy resin and the like.
However, tests have shown that with methylcellulose as binder, the thermal conductivity and compressive strength of the ceramic heat transfer module are hardly improved effectively. The reason is that the methyl cellulose mainly has the functions of thickening and improving surface activity, the binding force between the methyl cellulose and the filler is low, and when the ceramic heat transfer element is filled and dried at high temperature, the binding agent is partially melted to cause the filler to become loose and fall off, so that the purpose of filling the defects of the ceramic cannot be achieved.
The furan resin is brittle, so that the furan resin used as a binder causes the brittleness increase of the filler, the strength reduction and the disadvantage of filling the pore defects of the ceramic. The acid resistance of epoxy resin is poor, and the ceramic heat transfer element is used in the occasions of acid corrosion resistance, so that methyl cellulose, furan tree and epoxy resin are not selected as a binder.
The binder in the ceramic pore filler provided by the embodiment of the invention mainly comprises the following components: water glass, phenolic resin, silicone and the like. The water glass, the phenolic resin and the organic silicon have excellent acid corrosion resistance and physical and mechanical properties, strong binding power and easy curing, and are suitable for being used as a binding agent in the ceramic pore filler. The proportion of binder in the ceramic pore filler is generally 40 to 60% by weight.
The suspending agent in the ceramic pore filler provided by the embodiment of the invention mainly comprises the following components: polyvinyl chloride, polystyrene, polyvinyl alcohol, and the like. The proportion of suspending agent in the ceramic pore filler is generally from 5 to 12% by weight.
Polyvinyl alcohol as a water-soluble suspending agent is easy to decompose at a higher temperature, and shows that the polyvinyl alcohol is subjected to color change embrittlement at 100 ℃ and begins to decompose at 200 ℃. As a result, the filler is partially collapsed by shrinkage and fine voids are generated, resulting in a decrease in filling effect.
The dispersant in the ceramic pore filler provided by the embodiment of the invention is polyester resin, polytetrafluoroethylene emulsion and the like. The proportion of dispersant in the ceramic pore filler is generally from 5 to 12% by weight. The polyester resin has good adhesion, but the use temperature is lower than that of polytetrafluoroethylene. The polytetrafluoroethylene has the most stable chemical properties, can resist corrosive media such as acid and alkali and is a good dispersing agent. Therefore, polytetrafluoroethylene is mainly selected as the emulsion.
The ceramic pore filler provided by the embodiment of the invention usually selects graphite micro powder, silicon carbide micro powder, mullite micro powder and the like as fillers, wherein the graphite micro powder and the silicon carbide micro powder have good heat-conducting property, and the mullite has poor heat-conducting property. The particle size of the filler micropowder is generally 2 to 10 μm. The content of impurities in the filler is less than or equal to 1 percent. The proportion of filler in the ceramic pore filler is generally 16 to 50% by weight. When the filling material adopts mullite micropowder, the heat conductivity of the ceramic heat transfer module can not be improved almost after the filling material is impregnated, but the normal-temperature compressive strength is improved to a certain extent. This is because mullite has a lower thermal conductivity than a structural ceramic heat transfer body. Therefore, mullite micropowder is generally not selected as a filler.
Compared with the ceramic glaze filler, the multi-element infiltration filler filled in the structural ceramic heat transfer element provided by the embodiment of the invention has the advantages that the heat conductivity of the structural ceramic heat transfer element is averagely improved by about 28%, and the normal-temperature compressive strength is averagely improved by about 14%.
Compared with a binary filler of 'binder and filler', the multi-element infiltration filler provided by the embodiment of the invention has the advantages that the heat conductivity of the structural ceramic heat transfer element is averagely improved by about 5%, and the normal-temperature compressive strength is averagely improved by about 4%.
In a second aspect, an embodiment of the present invention further provides a method for preparing the pore filler for a ceramic heat transfer element, including the following steps: mixing the binder, the suspending agent, the dispersant and the filler, starting stirring, heating to 60-80 ℃ at the heating rate of 3-5 ℃/min until a uniform mixed solution is formed, and preparing the ceramic heat transfer element pore filler. In the preparation process, the adhesive, the suspending agent, the dispersing agent and the filler are only required to be mixed, heated and stirred until a uniform mixed solution is formed, and the product is obtained.
In a third aspect, an embodiment of the present invention further provides a method for filling pores of a ceramic heat transfer element with the above-mentioned pore filler for a ceramic heat transfer element, including: vacuum impregnating the ceramic heat transfer element in the ceramic heat transfer element pore filler under the vacuum condition, heating and curing the ceramic heat transfer element with the ceramic heat transfer element pore filler filled in pores, and controlling the vacuum degree to be 50-80KPa and the temperature to be 80-120 ℃ in the vacuum impregnating process.
In a fourth aspect, an embodiment of the present invention further provides a ceramic heat transfer element, where the ceramic heat transfer element is obtained by filling pores by using the above-mentioned filling method. The obtained ceramic heat transfer element has no internal pore defects and surface crack defects, and has high thermal conductivity and compressive strength.
The features and properties of the present invention are described in further detail below with reference to examples.
The ceramic glaze filler used below is prepared by the inventor, and is SiO in the following mass percentage 2 62wt％、Na 2 O 13wt％、Al 2 O 3 7wt％、K 2 O10 wt% and CaO 8 wt%, and adding water 30-50 wt% of the mixture.
The percentage of increase in thermal conductivity and the percentage of increase in room-temperature compressive strength were calculated in examples 2 to 4 and comparative examples 1 to 2 in a similar manner to that in example 1.
Example 1
Ceramic pore filler capable of resisting 260 ℃. By weight, 1000g of water glass, 100-150g of sodium fluosilicate, 100-200g of polyvinyl chloride, 100-200g of polytetrafluoroethylene and 450-700g of silicon carbide micropowder are taken.
The binder in this example was sodium water glass (liquid sodium silicate) having a density of 1.368-1.394(20 ℃)/(g/mL), modulus: 2.6-2.9; sodium oxide (Na) 2 O), omega/% > is more than or equal to 8.2; silicon dioxide (SiO) 2 ) Omega/% > is more than or equal to 26.0; modulus of elasticity3.10-3.40. Sodium fluosilicate is a curing agent (industrial grade). The suspending agent is general polyvinyl chloride resin. The dispersing agent is polytetrafluoroethylene emulsion with the concentration of 60 percent (mass ratio). The filler is alpha silicon carbide micro powder, and the grain diameter of the alpha silicon carbide micro powder is less than or equal to 6 mu m.
The preparation method comprises the following steps: pouring the sodium water glass solution into a mixing reaction kettle, and then sequentially adding the universal polyvinyl chloride resin, the polytetrafluoroethylene emulsion and the filler silicon carbide micro powder. Starting the stirrer, starting to heat to 60-80 ℃, wherein the heating speed is 3-5 ℃/min until the filler is uniformly mixed, and the method can be used for filling pores and crack defects of the ceramic heat transfer element.
Because the silicon carbide filler has high thermal conductivity, the polyvinyl chloride suspending agent and the polytetrafluoroethylene dispersing agent enable the silicon carbide filler to be dispersed more uniformly, mixed more fully and filled with better defect effect.
The comparison with the use of ceramic glaze filler, filler of the "binder + filler" type is as follows:
the average thermal conductivity of the ceramic element after the ceramic glaze filler is used is 20.0W/m.k, and the normal-temperature compressive strength is 110 MPa;
the average thermal conductivity of the ceramic heat transfer element using the binder and filler type filler is 24.50W/m.k, and the normal-temperature compressive strength is 120.20 MPa;
the average thermal conductivity of the ceramic heat transfer element filled with the multi-element filler of the present example was 25.8W/m.k, and the room-temperature compressive strength was 125.4 MPa.
The thermal conductivity of this example is improved by about 29% (calculated as (25.8-20)/20-29%) and the room temperature compressive strength is improved by about 14% (calculated as (125.4-110)/110-14%) compared to a ceramic heat transfer element with a ceramic glaze filler.
In this example, the thermal conductivity of the structural ceramic heat transfer element was increased by about 5.3% (calculated as (25.8-24.5)/24.5 ═ 5.3%) and the room temperature compressive strength was increased by about 4.3% (calculated as (125.4-120.2)/120.2 ═ 4.3%) as compared to the use of the "binder + filler" type filler.
Example 2
Ceramic pore filler capable of resisting 260 ℃. 1000g of water glass, 100-150g of sodium fluosilicate, 100-200g of polyvinyl chloride, 100-200g of polytetrafluoroethylene emulsion and 450-700g of graphite micropowder are taken according to weight.
The binder in this example is potassium water glass (liquid potassium silicate) having a density of 1.30-1.33(20 ℃)/(g/mL), modulus: 3.5-3.7; potassium oxide (Na) 2 O), omega/% > is more than or equal to 9.5; silicon dioxide (SiO) 2 ) Omega/% > is not less than 23.0; the suspending agent is general polyvinyl chloride resin. The dispersing agent is polytetrafluoroethylene emulsion with the concentration of 60 percent (mass ratio). The filler is artificial graphite micro powder, and the particle size of the filler is less than or equal to 5 mu m.
The preparation method comprises the following steps: pouring the potassium water glass solution into a mixing reaction kettle, and then sequentially adding the universal polyvinyl chloride resin, the polytetrafluoroethylene emulsion and the filler graphite micropowder. Starting the stirrer, and starting to heat to 70-90 ℃, wherein the heating speed is 3-5 ℃/min until the filler is uniformly mixed, and the method can be used for filling pores and crack defects of the ceramic heat transfer element.
Because the graphite filler has higher thermal conductivity, the polyvinyl chloride suspending agent and the polytetrafluoroethylene dispersing agent enable the silicon carbide filler to be dispersed more uniformly, mixed more fully and filled with better defect effect.
The comparison with the use of ceramic glaze filler, filler of the "binder + filler" type is as follows: the average thermal conductivity of the ceramic element using the ceramic glaze filler is 20.0W/m.k, and the normal-temperature compressive strength is 110 MPa;
the average thermal conductivity of the ceramic heat transfer element using the binder and filler type filler is 24.5W/m.k, and the normal-temperature compressive strength is 120.2 MPa;
the average thermal conductivity of the multi-element filler ceramic heat transfer element of the embodiment is 25.7W/m.k, and the room-temperature compressive strength is 125.4 MPa.
Compared with the ceramic heat transfer element using the ceramic glaze filler, the thermal conductivity of the heat transfer element is improved by about 28.5 percent, and the room-temperature compressive strength is improved by about 14 percent. In this example, the thermal conductivity of the structural ceramic heat transfer element was improved by about 5% and the room temperature compressive strength was improved by about 4.3% compared to the case of using the "binder + filler" type filler.
Example 3
A ceramic pore filler which can resist the temperature of 220 ℃. According to the weight, 1000g of modified phenolic resin, 100-200g of polyvinyl chloride, 100-200g of polytetrafluoroethylene emulsion and 600-800g of graphite micropowder are taken.
The binder in this example is a modified phenolic resin. The modified phenolic resin is prepared from phenolic resin and alpha and gamma dichloropropanol. Wherein the purity of the alpha and gamma dichloropropanol is more than or equal to 92 percent, and the density is 1.35-1.36g/cm 3 And the pH value is 6-7. 820g of phenolic resin and 180g of alpha and gamma dichloropropanol are taken, mixed and stirred uniformly at normal temperature. The suspending agent is general polyvinyl chloride resin. The dispersing agent is polytetrafluoroethylene emulsion with the concentration of 60 percent (mass ratio). The filler is artificial graphite micro powder, and the particle size of the filler is less than or equal to 5 mu m.
The preparation method comprises the following steps: pouring the modified phenolic resin solution into a mixing reaction kettle, and then sequentially adding the universal polyvinyl chloride resin, the polytetrafluoroethylene emulsion and the filler graphite micropowder. Starting the stirrer, heating to 50-80 deg.C at a speed of 3-5 deg.C/min, and mixing the filler uniformly to obtain the final product.
The comparison with the use of ceramic glaze filler, filler of the "binder + filler" type is as follows:
the average thermal conductivity of the ceramic element using the ceramic glaze filler is 20.0W/m.k, and the normal-temperature compressive strength is 110 MPa;
the average thermal conductivity of the ceramic heat transfer element using the binder and filler type filler is 24.5W/m.k, and the normal-temperature compressive strength is 120.2 MPa;
the average thermal conductivity of the multi-element filler ceramic heat transfer element of the embodiment is 25.4W/m.k, and the room-temperature compressive strength is 124.3 MPa.
Compared with the ceramic heat transfer element using the ceramic glaze filler, the thermal conductivity of the heat transfer element is improved by about 27 percent, and the room-temperature compressive strength is improved by about 13 percent. In this example, the thermal conductivity of the structural ceramic heat transfer element was improved by about 3.7% and the room temperature compressive strength was improved by about 3.5% compared to the case of using the "binder + filler" type filler.
Example 4
A ceramic pore filler capable of resisting the temperature of 220 ℃. According to the weight, 1000g of modified phenolic resin, 100-200g of polyvinyl chloride, 100-200g of polytetrafluoroethylene emulsion and 600-800g of silicon carbide micro powder are taken.
The binder in this example is a modified phenolic resin. The modified phenolic resin is prepared from phenolic resin and alpha and gamma dichloropropanol. Wherein the purity of the alpha and gamma dichloropropanol is more than or equal to 92 percent, and the density is 1.35-1.36g/cm 3 And the pH value is 6-7. 820g of phenolic resin and 180g of alpha and gamma dichloropropanol are taken, mixed and stirred uniformly at normal temperature. The suspending agent is general polyvinyl chloride resin. The dispersing agent is polytetrafluoroethylene emulsion with the concentration of 60 percent (mass ratio). The filler is silicon carbide micro powder with the grain diameter less than or equal to 5 mu m.
The comparison with the use of ceramic glaze filler, filler of the "binder + filler" type is as follows:
the average thermal conductivity of the ceramic element using the ceramic glaze filler is 20.0W/m.k, and the normal-temperature compressive strength is 110 MPa;
the average thermal conductivity of the ceramic heat transfer element using the binder and filler type filler is 24.5W/m.k, and the normal-temperature compressive strength is 120.2 MPa;
the average thermal conductivity of the ceramic heat transfer element using the multi-element filler of the invention is 25.5W/m.k, and the normal temperature compressive strength is 125.0 MPa.
Compared with the ceramic heat transfer element using the ceramic glaze filler, the thermal conductivity of the heat transfer element is improved by about 27.5 percent, and the room-temperature compressive strength is improved by about 13.6 percent. In this example, the thermal conductivity of the structural ceramic heat transfer element was improved by about 4.1% and the room temperature compressive strength was improved by about 4% compared to the case of using the "binder + filler" type filler.
Comparative example 1
Ceramic pore filler capable of resisting 260 ℃. By weight, 1000g of water glass, 100-150g of sodium fluosilicate, 100-200g of polyvinyl chloride, 100-200g of polytetrafluoroethylene emulsion and 600-1000g of silicon carbide micropowder are taken.
The binder in this example was sodium water glass (liquid sodium silicate) having a density of 1.368-1.394(20 ℃)/(g/mL), modulus: 2.6-2.9; sodium oxide (Na) 2 O), omega/% > is more than or equal to 8.2; silicon dioxide (SiO) 2 ) Omega/% > is more than or equal to 26.0; the modulus is 3.10-3.40. Sodium fluosilicate is a curing agent (industrial grade). The suspending agent is general polyvinyl chloride resin. The dispersing agent is polytetrafluoroethylene emulsion with the concentrationIs 60% (mass ratio). The filler is alpha-silicon powder with the grain diameter less than or equal to 6 mu m.
In the case of the filler with other components unchanged, the proportion of the filler silicon carbide micro powder is increased by 30 percent, the average thermal conductivity of the ceramic heat transfer element is 24.4W/m.k, and the defect filling effect of 120.6MPa of room-temperature compressive strength is reduced. Compared with the example 1 (the average thermal conductivity of the ceramic heat transfer element is 25.8W/m.k, and the normal-temperature compressive strength is 125.4 MPa.), the thermal conductivity of the structural ceramic heat transfer element is reduced by about 6 percent, and the normal-temperature compressive strength is also reduced by about 4 percent. The reason is that the phenomenon of uneven mixing of the filler occurs along with the increase of the proportion of the filler, so that the viscosity of the filler is reduced, the adhesive force is insufficient, and the filling effect is further influenced.
Comparative example 2
A ceramic pore filler which can resist the temperature of 220 ℃. 1000g of modified phenolic resin, 100-200g of polyvinyl alcohol, 100-200g of polytetrafluoroethylene emulsion and 600-800g of graphite micropowder are taken according to the weight.
The binder in this example is a modified phenolic resin. The modified phenolic resin is prepared from phenolic resin and alpha and gamma dichloropropanol. Wherein the purity of the alpha and gamma dichloropropanol is more than or equal to 92 percent, and the density is 1.35-1.36g/cm 3 And the pH value is 6-7. 820g of phenolic resin and 180g of alpha and gamma dichloropropanol are taken, mixed and stirred uniformly at normal temperature. The suspending agent is general polyvinyl alcohol. The dispersing agent is polytetrafluoroethylene emulsion with the concentration of 60 percent (mass ratio). The filler is artificial graphite micro powder, and the particle size of the filler is less than or equal to 5 mu m.
Compared with the example 4 (the average thermal conductivity of the ceramic heat transfer element is 25.5W/m.k, and the normal-temperature compressive strength is 125.0MPa), the thermal conductivity of the structural ceramic heat transfer element after being filled is reduced by about 15 percent, and the average thermal conductivity is 22.2W/m.k; the room temperature compressive strength can also be reduced by about 6 percent, and the average is 117.9 MPa. This is because polyvinyl alcohol, as a water-soluble suspending agent, is easily decomposed at a relatively high temperature, and exhibits discoloration and embrittlement at 100 ℃ and starts to decompose at 200 ℃. As a result of decomposition of polyvinyl alcohol, shrinkage collapse of the filler occurs and some fine voids occur, resulting in a decrease in thermal conductivity and compressive strength of the heat transfer ceramic.
In summary, the embodiments of the present invention provide a pore filler for a ceramic heat transfer element, a method for filling pores in a ceramic heat transfer element, and a ceramic heat transfer element. Wherein the effect of binder lets the filler can firmly bond together with ceramic body, and the effect of suspending agent lets filler homodisperse and binder intensive homogeneous mixing, and the effect of filler is the heat conductivity that improves the filler, strengthens ceramic body's mechanical strength, adopts this ceramic heat transfer element gas pocket filler can fill ceramic heat transfer element's gas pocket and crack defect completely, avoids appearing the medium cluster and mixes to can promote ceramic heat transfer element's heat conductivity and structural strength.
Compared with the ceramic glaze filler, the multi-element infiltration filler provided by the embodiment of the invention has the advantages that the heat conductivity of the filled structural ceramic heat transfer element is improved by about 28% on average, and the normal-temperature compressive strength is improved by about 14% on average.
Compared with a binary filler of 'binder and filler', the multi-element infiltration filler provided by the embodiment of the invention has the advantages that the heat conductivity of the structural ceramic heat transfer element is averagely improved by about 5%, and the normal-temperature compressive strength is averagely improved by about 4%.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. The pore filler of the ceramic heat transfer element is characterized by comprising the following components in parts by mass: 48-55 parts of binder, 8-10 parts of suspending agent, 8-10 parts of dispersant and 25-32 parts of filler;
the binder comprises at least one of water glass, organic silicon and modified phenolic resin;
the modified phenolic resin is prepared from phenolic resin and alpha and gamma dichloropropanol;
the suspending agent comprises at least one of polyvinyl chloride and polystyrene;
the dispersing agent is polytetrafluoroethylene emulsion;
the filler comprises at least one of graphite micropowder and silicon carbide micropowder.
2. The pore filler for ceramic heat transfer elements according to claim 1, wherein the graphite micropowder is selected from the group consisting of artificial graphite materials and the silicon carbide micropowder is α -silicon carbide micropowder.
3. The pore filler for ceramic heat transfer elements according to claim 1, characterized in that the particle size of the micro powder of the filler is 2-10 μm and the content of impurities in the micro powder is less than or equal to 1%.
4. A method for preparing the pore filler of the ceramic heat transfer element according to any one of claims 1 to 3, comprising the steps of: mixing the binder, the suspending agent, the dispersant and the filler, starting stirring, heating to 60-80 ℃ at the heating rate of 3-5 ℃/min until a uniform mixed solution is formed, and preparing the ceramic heat transfer element pore filler.
5. A method of filling pores in a ceramic heat transfer element, comprising: and (2) carrying out vacuum infiltration on the ceramic heat transfer element in the ceramic heat transfer element pore filler under the vacuum condition, and then heating and curing the ceramic heat transfer element with pores filled with the ceramic heat transfer element pore filler, wherein the ceramic heat transfer element pore filler is the ceramic heat transfer element pore filler prepared by any one of claims 1 to 3 or the preparation method of claim 4.
6. The method for filling pores of a ceramic heat transfer element according to claim 5, wherein the degree of vacuum is controlled to 50 to 80KPa and the temperature is controlled to 80 to 120 ℃ during the vacuum infiltration.
7. A ceramic heat transfer element obtained by pore-filling the ceramic heat transfer element by the filling method according to claim 5 or 6.
CN202110494518.5A 2021-05-07 2021-05-07 Pore filler for ceramic heat transfer element, method for filling pores in ceramic heat transfer element, and ceramic heat transfer element Active CN113105269B (en)

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