CN115700234B - Fiber-reinforced low-density porous heat insulation material and preparation method thereof - Google Patents

Fiber-reinforced low-density porous heat insulation material and preparation method thereof Download PDF

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CN115700234B
CN115700234B CN202211325320.5A CN202211325320A CN115700234B CN 115700234 B CN115700234 B CN 115700234B CN 202211325320 A CN202211325320 A CN 202211325320A CN 115700234 B CN115700234 B CN 115700234B
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CN115700234A (en
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姚润占
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Guangzhou Shitao New Material Co ltd
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Abstract

The invention discloses a fiber reinforced low-density porous heat insulation material, which is prepared by adopting a dry pressing method, and the preparation raw materials of the fiber reinforced low-density porous heat insulation material comprise the following raw materials in percentage by weight: 50-99% of compressible powder and 1-50% of ceramic fiber; the ceramic fiber consists of a refractory fiber and an infrared shading fiber, wherein the infrared shading fiber is at least one of a carbon fiber, a titanium oxide fiber, a silicon carbide fiber, a zirconia fiber, a zirconium silicate fiber, a potassium hexatitanate fiber and an iron oxide fiber, the ratio of the length of the infrared shading fiber to the diameter of the infrared shading fiber is more than or equal to 100, and the diameter of the infrared shading fiber is less than or equal to 20 mu m. According to the fiber reinforced low-density porous heat insulation material, the infrared shading fiber is adopted to reduce the heat conductivity of the heat insulation material at a high temperature section without adding a powdery infrared shading agent, so that the effects of effectively improving the bending strength, the highest using temperature and reducing the heat conductivity of the heat insulation material can be achieved.

Description

Fiber-reinforced low-density porous heat insulation material and preparation method thereof
Technical Field
The invention relates to a fiber reinforced low-density porous heat insulation material and a preparation method thereof, in particular to a fiber reinforced low-density porous heat insulation material which is prepared by a dry pressing method without adding powdery infrared shading fibers in preparation raw materials, and belongs to the fields of heat insulation materials and environmental protection.
Background
Global warming is the consequence of human behavior causing changes in the earth's climate. "carbon" is a natural resource composed of carbon elements such as petroleum, coal, wood, etc. "carbon" is consumed much more and the basic "carbon dioxide" that causes global warming is also produced much more. With human activities, global warming also affects people's lifestyle, bringing about more and more ecological, climate and other problems. In order to reduce the emission of carbon dioxide, industries with high energy consumption like steel, cement, nonferrous metals and the like adopt various heat preservation and insulation materials to reduce energy loss so as to reduce the consumption of fossil energy. Most representative of the heat insulating materialsThe product is the silica aerogel. Silica aerogel is a typical low density porous insulating material with high porosity (85% -99%), small average pore size (2-50 nm), low density (30-150 kg/m) 3 ) And a thermal conductivity lower than that of air in a low temperature range (0.01 to 0.02W/(mK)). However, in the use at high temperatures, the thermal conductivity of silica aerogel increases rapidly, mainly because silica is almost totally transparent to near infrared radiation of 2.5-8 μm, whereas radiation at room temperature-1000 ℃ is mainly in this band, and pure silica aerogel has poor performance of inhibiting high temperature radiation because radiation heat transfer at high temperature is a main energy transfer mode.
In order to improve the heat insulation performance of silica aerogel at high temperature, the main mode is to add an infrared opacifier into the aerogel to reduce the radiation heat conductivity at high temperature. The opacifier powder has stronger scattering and absorbing effects on radiation, and the proper type of opacifier is added, so that the extinction coefficient of aerogel can be increased to a great extent, and the high-temperature radiation heat conductivity is reduced, thereby improving the high-temperature heat insulation performance of the aerogel. In general, the extinction coefficient of aerogel is related to the addition amount of infrared opacifier, and the larger the addition amount of infrared opacifier is, the larger the extinction coefficient is, and the stronger the infrared radiation resistance is. However, the amount of the infrared light-shielding agent added is not as large as possible. At first, due to the addition of the infrared opacifier, the thermal conductivity of the silicon dioxide aerogel is obviously reduced at a high temperature, but the thermal conductivity is not reduced and reversely increased after a certain value is reached. This is mainly because the infrared opacifier is a powder material and the average particle size is generally less than 5 μm, so the tap density is quite high, and when a large amount of infrared opacifier is added to silica aerogel, the bulk density of the aerogel is remarkably improved, which increases solid heat conduction at high temperature and improves thermal conductivity. In the patent CN105967728B, zirconium oxide and zirconium silicate are used as infrared opacifiers, and the maximum addition amount reaches 30%, so that the fiber-reinforced silica-alumina composite aerogel is prepared. Due to zirconium silicate (4.56 g/cm) 3 ) And zirconia (5.85 g/cm) 3 ) The true density of the aerogel is quite high, and the bulk density of the aerogel is increased by adding a large amount of the aerogel, so that the lightweight of the aerogel is lostThe advantage of the melting is that the solid heat conduction is increased, which is unfavorable for reducing the heat conductivity.
In order to reduce the influence on solid heat conduction and bulk density caused by infrared opacifiers, patent CN114524638A adopts silicon carbide nanowire aerogel, carbon nanotube aerogel and zirconia aerogel to prepare a nanofiber aerogel composite material, and the bulk density of the prepared composite material is only 20-60 kg/m because the tap density of the infrared opacifiers is quite low 3 Has good thermal conductivity (0.0185W/(m.k)) at room temperature. However, the aerogel composite has the common problem of all aerogel materials: the preparation is complicated. Firstly, a plurality of organic and inorganic materials are needed, acid and alkali and a binder are added in a matching way, the precursor is obtained by freeze drying for 8 days at the temperature of minus 90 ℃, then the precursor and the catalyst are repeatedly pressurized and depressurized in a reaction kettle under the supercritical condition, and finally the aerogel composite material can be obtained. The complicated preparation process is not suitable for mass production, and the size of the reaction kettle also limits the size of the aerogel heat insulation material and limits the use of the aerogel heat insulation material.
In addition, the patent CN106747265B first attaches the infrared opacifier to the fiber mat, and then prepares the aerogel composite material of the self-assembled opacifier fiber by using the fiber mat and the silica aerogel together. The aerogel composite material also has good heat conductivity at room temperature, but the preparation process is quite complex and complicated, 4 steps are needed when the infrared opacifier is self-assembled and loaded on the fiber, each step needs to be repeated for up to 10 times, the preparation process of the composite material needs to take a plurality of weeks, and a certain step is in error, so that the prior work can be abandoned. The fibers used in the patent are all organic polymer fibers, and the maximum use temperature is less than 300 ℃, so that the fiber is not suitable for use at high temperature. The same thought is used, and patent CN110698101B is also used, namely, zirconium silicate coating modified refractory fiber felt is obtained on the surface of refractory fiber by dipping zirconium silicate composite solution, surfactant and lithium fluoride, and vacuum filtration, drying and sintering. And then compounding the modified fiber felt with the silica-alumina composite sol prepared by a complex process, and aging for 3 days, ion exchange, modification for 2 days, ion exchange and drying for several days to obtain the infrared shielding coating modified fiber reinforced aerogel heat insulation material. Although the thermal conductivity of the thermal insulation material is low (0.036W/(m·k) at room temperature), the whole process also takes several weeks, which does not have the possibility of mass production.
In summary, in order to achieve the purposes of energy conservation and emission reduction, the current porous heat insulation material has four problems: firstly, for a porous heat insulation material represented by silica aerogel, as the tap density of an infrared opacifier is higher, after the infrared opacifier is added into the silica aerogel, the bulk density of the aerogel is increased, the low density characteristic of the aerogel is weakened, solid heat conduction is also increased, and the heat conductivity is not reduced under the conditions of low temperature and high temperature; secondly, the preparation process of the porous heat insulation material represented by aerogel at present is complicated, so that not only a plurality of organic and inorganic reagents are needed and the possibility of environmental pollution exists, but also a plurality of equipment such as freeze drying, supercritical drying, high-pressure reaction kettles and the like are needed, and the large-scale industrial production is not facilitated; thirdly, for the fiber reinforced low-density porous heat insulation material, if the addition amount of the fiber is too small, the strength of the heat insulation material is insufficient, and the handholding property and the processing property are insufficient; and if the amount of the fiber is too large, the solid heat conduction between the fibers increases, which affects the thermal conductivity of the heat insulating material. The fiber only achieves the single purpose of increasing the strength, and the functionality is slightly insufficient; fourth, the highest use temperature of the fiber reinforced aerogel heat insulation material or nano heat insulation material at present is generally not higher than 1300 ℃, which seriously affects the use range of the heat insulation material.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the fiber reinforced low-density porous heat insulation material with larger size and higher maximum using temperature. Meanwhile, another object of the present invention is to provide a method for preparing a fiber reinforced low-density porous heat insulating material which does not require any binder, has low cost, and can prepare a large-sized and low-thermal conductivity.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing method, and the preparation raw materials of the fiber reinforced low-density porous heat insulation material comprise the following raw materials in percentage by mass: 50-99% of compressible powder and 1-50% of ceramic fiber;
the ceramic fiber consists of refractory fiber and infrared shading fiber, wherein the refractory fiber accounts for 0-49% of the total mass of the raw material for preparing the fiber reinforced low-density porous heat insulation material, and the infrared shading fiber accounts for 1-50% of the total mass of the raw material for preparing the fiber reinforced low-density porous heat insulation material;
the infrared shading fiber is at least one of carbon fiber, titanium oxide fiber, silicon carbide fiber, zirconia fiber, zirconium silicate fiber, potassium hexatitanate fiber and ferric oxide fiber, the ratio of the length to the diameter of the infrared shading fiber is more than or equal to 100, and the diameter of the infrared shading fiber is less than or equal to 20 mu m.
According to the fiber reinforced low-density porous heat insulation material, the infrared light shielding agent powder which is conventionally used is not added, but the infrared light shielding fiber is creatively used, so that not only is the infrared radiation resistance of the heat insulation material at high temperature improved, but also the strength of a blank body is improved under the condition that the stacking density of the porous material is not remarkably improved, the handholding performance is improved, and the yield is improved.
In the preparation raw materials of the fiber reinforced low-density porous heat insulation material, the ceramic fiber consists of two parts of refractory fiber and infrared shading fiber, wherein the infrared shading fiber comprises at least one of carbon fiber (only used in an oxygen-free environment), titanium oxide fiber, silicon carbide fiber, zirconium oxide fiber, zirconium silicate fiber, potassium hexatitanate fiber and ferric oxide fiber; and the length-diameter ratio (the ratio of the length to the diameter) of the infrared shading fiber is more than or equal to 100, and the diameter of the infrared shading fiber is less than or equal to 20 mu m. The present inventors studied the shape and size of the infrared light-shielding fiber in the selection process of the infrared light-shielding fiber, and found that for spherical, spheroid, cubic and cylindrical (fiber) infrared light-shielding fiber, the spheroid infrared light-shielding fiber has a maximum average extinction coefficient of Luo Lansi at 500 ℃ and a minimum cylindrical extinction coefficient, which is about 30% higher than that of cylindrical in numerical terms. In addition, it is noted that for cylindrical infrared opacifier fibers, the average extinction coefficient at 500 ℃ Luo Lansi is almost the same for both 5 and 50 aspect ratios, so the extinction coefficient and the aspect ratio of cylindrical (fibrous) infrared opacifier fibers are not in great relationship. Through experimental finding, the inventor finally selects the infrared shading fiber with the length-diameter ratio of more than or equal to 100. In addition, the inventor finds through experiments that the smaller the diameter of the infrared shading fiber is, the better the scattering effect is, and thus the better the heat insulation effect is, and in order to achieve the proper heat insulation effect, the diameter of the infrared shading fiber is smaller than or equal to 20 mu m.
In the preparation raw materials of the fiber reinforced low-density porous heat insulation material, the addition amount of the infrared shading fiber accounts for 1-50% of the total mass of the preparation raw materials of the fiber reinforced low-density porous heat insulation material. If the addition amount of the infrared shading fiber is too small, the heat radiation amount of the heat insulation material at high temperature can be increased, and the heat insulation effect is affected; in contrast, since the tap density of the infrared shielding fiber is much smaller than that of the infrared shielding agent of the same material, but is much larger than that of the compressible powder, if the addition amount of the infrared shielding agent is too large, the bulk density of the heat insulation material is remarkably increased, so that the solid state heat conduction is increased, and the reduction of the density of the heat insulation material and the reduction of the heat conductivity of the heat insulation material are not facilitated.
As a preferable implementation mode of the fiber reinforced low-density porous heat insulation material, the infrared shading fiber accounts for 5-30% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material. As a more preferable embodiment of the fiber reinforced low-density porous heat insulation material, the infrared shading fiber accounts for 10-20% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material. Through trial and error, the inventor of the present application has found that when the addition amount of the infrared shielding fiber is within the preferable and more preferable ranges, a fiber-reinforced low-density porous heat insulating material having better comprehensive properties such as heat insulating effect, bulk density, thermal conductivity and the like can be obtained.
As a preferable embodiment of the fiber reinforced low-density porous heat insulating material, the ratio of the length to the diameter of the infrared shielding fiber is 100-1000, and the diameter of the infrared shielding fiber is less than or equal to 10 mu m. As a more preferable embodiment of the fiber-reinforced low-density porous heat insulating material of the present application, the ratio of the length to the diameter of the infrared shielding fiber is 200 to 500, and the diameter of the infrared shielding fiber is 5 μm or less. If the ratio of the length to the diameter of the infrared shading fiber is too large, the uniform distribution of the infrared shading fiber in the fiber reinforced low-density porous heat insulation material is influenced, and the infrared extinction is influenced; conversely, if the ratio of the length to the diameter of the infrared shielding fibers is too short, it is insufficient for the infrared shielding fibers to reinforce the low density insulation. Accordingly, the present inventors finally selected the infrared light-shielding fiber having a ratio of length to diameter of 100 to 1000, more preferably, 200 to 500, according to the result of the study. The inventors of the present application found in experiments that the smaller the diameter of the infrared light-shielding fiber, the better the scattering effect, and thus the better the heat-insulating effect, the diameter of the infrared light-shielding fiber in the present application is preferably 10 μm or less, and more preferably, the diameter of the infrared light-shielding fiber is 5 μm or less, for better heat-insulating effect.
As a preferred embodiment of the fiber-reinforced low-density porous heat insulating material of the present invention, the bulk density of the fiber-reinforced low-density porous heat insulating material is 100 to 600kg/m 3 . The bulk density is related to the flexural strength and thermal conductivity of the fiber reinforced low density porous insulation material. For the present invention, since the infrared shielding powder is not used, but the infrared shielding fiber is creatively used to improve the infrared radiation resistance of the heat insulating material in the high temperature section, even if the bulk density is as small as 100kg/m 3 The fiber reinforced low density porous thermal insulation material also has a flexural strength of at least 0.1MPa. But if the bulk density of the insulating material is less than 100kg/m 3 ThenThe bending strength of the fiber reinforced low-density porous heat insulation material is difficult to ensure, and the fiber reinforced low-density porous heat insulation material is easy to damage during processing and use; in contrast, if the bulk density is more than 600kg/m 3 The density is increased to occupy the porosity in the heat insulation material, so that the solid conduction is increased, and the heat conductivity of the heat insulation material is affected. Therefore, the bulk density of the fiber reinforced low density porous heat insulating material of the invention is 100-600 kg/m 3 。
As a preferred embodiment of the fiber-reinforced low-density porous heat insulating material of the present invention, the bulk density of the fiber-reinforced low-density porous heat insulating material is 200 to 450kg/m 3 . As a more preferable embodiment of the fiber-reinforced low-density porous heat insulating material of the present invention, the bulk density of the fiber-reinforced low-density porous heat insulating material is 250 to 350kg/m 3 . In order to balance the flexural strength and thermal conductivity, it is preferable that the bulk density of the fiber reinforced low density porous thermal insulation material is 200kg/m 3 ～450kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the More preferably, the fiber reinforced low density porous insulation material has a bulk density of 250kg/m 3 ～350kg/m 3 。
As a preferred embodiment of the fiber reinforced low density porous heat insulating material of the present invention, the compressible powder is at least one of aerogel powder and gas phase oxide powder; the aerogel powder comprises at least one of silica aerogel powder and alumina aerogel powder; the gas-phase oxide powder comprises at least one of gas-phase silicon oxide powder and gas-phase aluminum oxide powder. The compressible powder belongs to nanoscale materials, so that the compressible powder has a large specific surface area, can be easily attached to other materials, can serve as a dispersing agent when being inlaid between the raw materials, and can enlarge the volume of the mixed raw materials, so that the mixed raw materials can be directly subjected to dry pressing and molding. Because of the nano-size property of the compressible powder, the pore diameter of the formed air holes is smaller than 50-70 nm of the average free path of air gas molecules, and the heat conduction caused by air convection is reduced to the minimum. In the fiber reinforced low-density porous heat insulation material, the more the addition amount of the compressible powder is, the smaller the density of the blank body after compression molding is, and the lower the solid heat conduction is, so that the thermal conductivity of the fiber reinforced low-density porous heat insulation material is lower; the disadvantage is that the strength of the blank is insufficient due to the low density, the handiness is insufficient, and the cracking is easy to occur. If the compressible powder is not sufficiently added, the strength of the blank can be improved on one hand, but the increase of solid heat conduction caused by high density can quickly improve the heat conductivity of the fiber reinforced low-density porous heat insulation material and reduce the heat insulation performance. The inventors of the present invention have repeatedly verified that the addition amount of the compressible powder is 50 to 99% of the total mass of the compressible powder and the ceramic fiber.
In addition, for different kinds of compressible powders, since the specific surface area of aerogel powder is generally larger than that of the same type of gas-phase oxide powder, the compression ratio of aerogel powder is larger than that of gas-phase oxide powder. Under the condition of the same addition amount, the density of the blank body is smaller than that of the gas-phase oxide powder after the aerogel powder is molded. For the same aerogel powder, the bulk density of the blank molded by the silica aerogel powder is smaller than that of the blank molded by the alumina aerogel powder due to the difference of the true densities. In addition, for the highest use temperatures, both aerogel powders and vapor phase oxide powders are amorphous powders. And the crystallization temperatures of silica and alumina are different. Wherein the crystallization temperature of silica is typically less than 1000 c and the crystallization temperature of alumina is typically in excess of 1500 c. Once the crystallization temperature of the material is reached, severe volume shrinkage and deformation are accompanied, meaning the end of the life of the insulation material. The ratio of silica aerogel to fumed silica is tightly controlled if the maximum service temperature of the fiber reinforced low density porous insulation material is required to exceed 1000 c.
As a preferred embodiment of the fiber-reinforced low-density porous heat insulating material, the refractory fiber is at least one of glass fiber, aluminum silicate fiber, mullite fiber, aluminum oxide fiber, silicon oxide fiber and silicon nitride fiber, and the diameter of the refractory fiber is less than or equal to 20 μm and the length of the refractory fiber is 1-100 mm. Compared with the infrared shading fiber, the fire-resistant fiber has no infrared reflection and scattering effects, but the material of the fire-resistant fiber has smaller shrinkage rate at high temperature than the infrared shading fiber, so that the addition of the fire-resistant fiber can effectively improve the highest use temperature of the fiber reinforced low-density porous heat insulation material and resist the heat-induced shrinkage rate caused by compressible powder.
As a preferable implementation mode of the fiber reinforced low-density porous heat insulation material, the compressible powder accounts for 70-90% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material. The inventor discovers that when the compressible powder accounts for 70-90% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material, the properties such as ligand strength and heat conductivity of the material can be better considered.
As a preferable embodiment of the fiber reinforced low-density porous heat insulation material, the refractory fiber accounts for 5-40% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material. As with the infrared shading fiber, the addition of a proper amount of refractory fiber can effectively improve the green strength of the heat insulation material. If the amount of the flame-retardant fiber and the infrared shielding fiber added is small, the strength of the fiber-reinforced low-density porous material molded body is small, and the molded body is not sufficient in handiness and is easily broken during transportation. The refractory fibers described in CN108017368A are used in an amount of up to 10%, resulting in insufficient strength to handle the processing, packaging and transportation requirements, both in the green body after molding and in the finished sintered product. However, excessive addition of refractory fibers has two disadvantages: firstly, the addition amount of the infrared shading fiber is extruded, so that the heat insulation performance of the heat insulation material at high temperature is affected; second, as with the infrared shading fiber, the tap density of the refractory fiber is much greater than that of the compressible powder, so that if the refractory fiber is excessively added, the bulk density of the heat insulation material is obviously increased, and the realization of the light weight of the heat insulation material and the improvement of the heat conductivity are finally affected. In conclusion, the inventor of the present application considers that the addition amount of the refractory fiber is preferably 5% -40% of the total mass of the preparation raw material of the fiber reinforced low-density porous heat insulation material through repeated experiments.
As a preferable embodiment of the fiber reinforced low-density porous heat insulation material, the refractory fiber accounts for 10-30% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material. In order to better balance the bending strength, the heat conductivity and the highest use temperature of the fiber reinforced low-density porous heat insulation material, the addition amount of the refractory fiber is 10 to 30 percent of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material.
As a preferred embodiment of the fiber reinforced low density porous insulation material of the present invention, the refractory fiber has a slag content of less than 10%. As a more preferred embodiment of the fiber reinforced low density porous insulation material of the present invention, the slag content of the refractory fiber is less than 1%. During the preparation of refractory fibers, there is generally a considerable proportion of slag. Such slag does not increase the strength of the insulation material nor decrease the thermal conductivity and thermal expansion coefficient of the insulation material, so that when selecting refractory fibers, refractory fibers having a slag content of less than 10% should be selected, and more preferably, refractory fibers having a slag content of less than 1%.
As a preferred embodiment of the fiber reinforced low density porous thermal insulation material of the present invention, the fiber reinforced low density porous thermal insulation material has a flexural strength of greater than 0.1MPa. If the bending strength is less than 0.1MPa, it is difficult to ensure the overall strength of the fiber reinforced low-density porous heat insulating material, and breakage may occur during handling, installation and use, affecting use. Factors influencing the bending strength are mainly the bulk density of the insulation material and the amount of ceramic fibers added. Under the condition of the same composition, the larger the stacking density of the heat insulation material is, the larger the bending strength is; the larger the ceramic fiber ratio, the greater the bending strength of the insulation material under the same bulk density.
As a preferred embodiment of the fiber reinforced low density porous thermal insulation material of the present invention, the fiber reinforced low density porous thermal insulation material has a maximum use temperature of 800 ℃ or higher. The highest use temperature of the fiber reinforced low-density porous heat insulation material is more than or equal to 800 ℃, and the fiber reinforced low-density porous heat insulation material can be used for a long time at 1500 ℃.
In the present invention, the definition of the maximum use temperature is: if the linear shrinkage is less than 2% when maintained at the specified temperature for 24 hours, it is considered that the thermal insulation material of the composition can be operated at the specified temperature, that is, the highest use temperature of the thermal insulation material of the composition. In contrast, if the linear shrinkage of the composite insulation material at the specified temperature exceeds 2%, then additional samples need to be taken for testing at lower temperatures until the linear shrinkage after 24 hours holding at the test temperature is less than 2%, and the maximum service temperature can be determined.
According to the studies of the present inventors, the maximum use temperature of the fiber reinforced low density porous heat insulating material is mainly related to two factors: the material of the first compressible powder and the material of the second compressible powder and the proportion of the first compressible powder in the raw materials for preparing the fiber reinforced low-density porous heat insulation material; second, the material, content, diameter and slag content of the ceramic fiber. The compressible powder is at least one of aerogel powder and gas-phase oxide powder. The aerogel powder comprises at least one of silica aerogel powder and alumina aerogel powder; the gas-phase oxide powder comprises at least one of gas-phase silicon oxide powder and gas-phase aluminum oxide powder. Since the crystallization temperature of aluminum dioxide is higher than that of silicon dioxide, in the composition of the compressible powder of the fiber-reinforced low-density porous heat insulating material, if the ratio of the aluminum dioxide aerogel powder or the vapor phase aluminum dioxide is high, the highest use temperature of the fiber-reinforced low-density porous heat insulating material of the component is higher. According to the study of the inventor, when the ratio of the silica aerogel to the fumed silica in the compressible powder reaches 100%, and the addition amount of the refractory fiber is 1%, the maximum use temperature of the fiber reinforced low-density porous heat insulation material is 800 ℃; when the ratio of the aluminum dioxide aerogel powder to the gas-phase aluminum dioxide in the compressible powder reaches 100 percent and the addition amount of the ceramic fiber is more than or equal to 10 percent, the highest use temperature of the fiber reinforced low-density porous heat insulation material reaches 1200 ℃. Regarding ceramic fibers, the material is the most important factor affecting the refractoriness of the ceramic fibers. In the present application, the ceramic fibers are classified into infrared light-shielding fibers and fire-resistant fibers, and each fiber has a different fire-resistant temperature, resulting in different heat-induced shrinkage at the same temperature. The thermal shrinkage rate of titanium oxide fiber and ferric oxide fiber in infrared shading fiber is higher, and the thermal shrinkage rate of glass fiber and silicon oxide fiber in fire-resistant fiber is higher; the thermal shrinkage rate of the zirconia fiber and the zirconium silicate fiber in the infrared shading fiber and the alumina fiber and the mullite fiber in the refractory fiber is smaller. The ceramic fiber has small heat-induced shrinkage, and the shrinkage of the fiber reinforced low-density porous heat insulation material prepared by the ceramic fiber is relatively small. On the other hand, the content of ceramic fibers is also of critical importance. According to the study of the present inventors, the maximum use temperature of the fiber reinforced low density porous insulation material, in which silica aerogel, fumed silica, accounts for 100% of the compressible powder without any ceramic fibers, is 700 ℃. From the above study, it is found that when the ratio of silica aerogel or fumed silica in the compressible powder reaches 100% and the addition amount of the ceramic fiber is 1% or more, the maximum use temperature of the fiber-reinforced low-density porous heat insulating material is 800 ℃, and the maximum use temperature is increased by 100 ℃. Whichever ceramic fiber material is added into the heat insulation material, the heat-induced shrinkage rate of the heat insulation material can be improved, and the highest use temperature of the heat insulation material can be improved. And the more the ceramic fiber is in the heat insulation material, the higher the corresponding highest use temperature of the heat insulation material. In addition, when the amount of the slag is equal, the lower the slag content, the higher the fiber ratio by the same weight, the more effectively the heat-induced shrinkage can be prevented.
As a preferred embodiment of the fiber reinforced low density porous insulation material of the present application, the fiber reinforced low density porous insulation material has a thermal conductivity of less than 0.1W/mK at 800 ℃. The thermal conductivity of the fiber reinforced low-density porous heat insulation material is mainly related to the bulk density and the content of the infrared shading fiber. Bulk density: the smaller the bulk density, the less solid state heat conduction, and therefore the lower the thermal conductivity, at the same composition; infrared shading fiber content: the higher the content of the infrared shielding fiber, the smaller the heat loss due to infrared heat radiation at high temperature, and the lower the thermal conductivity. However, the addition amount of the infrared shielding fiber is not as large as possible, and if the addition amount of the infrared shielding fiber is too large, the addition amount of the compressible powder is squeezed. If the amount of the compressible powder to be added is too small, the bulk density of the molded article becomes too high, and the solid heat conduction increases, resulting in an increase in the thermal conductivity.
As a preferred embodiment of the fiber reinforced low density porous thermal insulation material of the present application, the compressible powder is composed of silica aerogel and fumed silica, and the refractory fiber accounts for 1% of the total mass of the raw material for preparing the fiber reinforced low density porous thermal insulation material. As described above, the present inventors have found that when the ratio of silica aerogel, fumed silica in the compressible powder is 100%, and the addition amount of the refractory fiber is 1% of the total mass of the raw material for preparing the fiber-reinforced low-density porous heat insulating material, the maximum use temperature of the fiber-reinforced low-density porous heat insulating material is 800 ℃;
As a preferred embodiment of the fiber reinforced low-density porous heat insulation material, the compressible powder consists of aluminum dioxide aerogel and gas phase aluminum dioxide, and the addition amount of the ceramic fiber is more than or equal to 10% of the total mass of the raw materials for preparing the fiber reinforced low-density porous heat insulation material. As described above, when the ratio of the alumina aerogel powder to the vapor phase alumina in the compressible powder reaches 100% and the addition amount of the ceramic fiber is 10% or more of the total mass of the raw materials for preparing the fiber-reinforced low-density porous heat insulation material, the maximum use temperature of the fiber-reinforced low-density porous heat insulation material reaches 1200 ℃.
In addition, in order to realize the purposes of the invention that the fiber reinforced low-density porous heat insulation material with large size and low heat conductivity can be prepared without using any binder and with low cost, the invention adopts the following technical scheme: a method for preparing a fiber reinforced low density porous thermal insulation material, the method being a dry press forming method and comprising the steps of:
(1) Mixing the compressible powder and the ceramic fiber according to a proportion;
(2) Introducing the raw materials mixed in the step (1) into a die for compression molding, wherein the pressure is 10-3000 kgf/cm 2 Pressing to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) at 800-1500 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The preparation method of the fiber reinforced low-density porous heat insulation material has simple steps, does not need to add any binder or water or other liquid, can prepare the fiber reinforced low-density porous heat insulation material with large size and high strength without drying, and has the advantages of low labor and material cost.
As a preferred embodiment of the method for preparing a fiber reinforced low density porous heat insulating material of the present invention, the step (1) is performed by mixing with high-speed stirring or ball milling stirring. When mixing is performed by high-speed stirring, the mixing time is not less than 5 minutes. The compressible powder and the ceramic fiber can be well mixed by high-speed stirring and mixing, and the mixing time is generally not less than 5 minutes in order to ensure the uniformity of mixing. When the mixing is carried out by ball milling and stirring, the stirring time is not less than 1 hour.
As a preferred embodiment of the method for producing a fiber-reinforced low-density porous heat insulating material of the present invention, the pressing time in the step (2) is not less than 1 minute. In the pressing process, the pressing time is generally not less than 1 minute in order to secure the strength of the green body obtained after pressing.
As a preferred embodiment of the method for producing a fiber-reinforced low-density porous heat insulating material of the present application, the sintering time in the step (3) is not less than 1 hour. The sintering temperature is generally determined according to the material and the addition amount of the compressible powder and the ceramic fiber, and the heat preservation time during sintering is generally determined according to the thickness of the fiber reinforced low-density porous heat insulation material and is generally not less than 1 hour.
The fiber reinforced low-density porous heat insulation material is prepared from compressible powder and ceramic fiber, wherein the ceramic fiber consists of refractory fiber and infrared shading fiber, the powder infrared shading fiber which is commonly added in the traditional heat insulation material is not added, the heat conductivity of the heat insulation material at a high temperature section is creatively reduced by using the infrared shading fiber, the tap density of the shading fiber is smaller than that of the powder infrared shading agent, the stacking density of the prepared heat insulation material can be effectively reduced, the solid heat conduction is reduced, the strength of a heat insulation material blank is enhanced while the density is reduced, and the blank has enough handholding performance under the condition that any binder and curing agent are not added, so that the yield is improved. Meanwhile, the inventor optimizes the addition amount and the external dimension of the infrared shading fiber by controlling the content of each component, the selection of the infrared shading fiber and the like, so that the thermal conductivity of the heat insulation material at a high temperature (800 ℃) is further reduced, the addition of the refractory fiber can also effectively improve the strength of the heat insulation material blank, and the highest use temperature of the heat insulation material can also be effectively improved, so that the highest use temperature of the fiber reinforced low-density porous heat insulation material is improved to more than 800 ℃, the highest use temperature can reach 1500 ℃, and the use range of the fiber reinforced low-density porous heat insulation material is widened.
The preparation method of the fiber reinforced low-density porous heat insulation material is a dry pressing molding method, has the advantages of simple step process, no addition of organic or binder, no addition of liquid such as water and the like, saving of cost required by subsequent drying, low cost of labor and materials, and large-size and low-heat conductivity performance of the prepared fiber reinforced low-density porous heat insulation material. The preparation method of the fiber reinforced low-density porous heat insulation material has the advantages of high preparation speed and low production cost, greatly shortens the production flow and is easy for mass production.
Detailed Description
For better illustrating the objects, technical solutions and advantageous effects of the present invention, the present invention will be further described with reference to specific embodiments.
Unless otherwise indicated, all materials used in the examples of the present invention may be obtained directly from commercial sources or prepared according to methods conventional in the art.
The refractory fibers used in the examples described below were 20 μm or less in diameter and 1 to 100mm in length, and the slag content of the refractory fibers was 10% or less.
The bulk densities described below were all tested using the following procedure:
The mass of the prepared heat insulation material is weighed by a weight (such as a platform scale, a platform scale and the like) (the unit is kg). The length, width and height (in m) of the fiber reinforced low density porous insulation material were measured with a ruler or tape measure. Then according to the formula: bulk density = mass/length/width/height (in kg/m 3), the bulk density can be obtained.
Example 1
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 99% of compressible powder and 1% of ceramic fiber;
the compressible powder is aluminum dioxide aerogel, the ceramic fiber is an infrared shading fiber, and the infrared shading fiber is a silicon carbide fiber;
the diameter of the infrared shading fiber is 20 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 100.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 5 minutes, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 10kgf/cm 2 Pressing for 30min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 3 hours at 1200 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 210kg/m 3 。
Example 2
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 50% of compressible powder and 50% of ceramic fiber;
the compressible powder is fumed silica powder, the ceramic fibers are infrared shading fibers and refractory fibers in a mass ratio of 2:3, the infrared shading fibers are titanium oxide fibers, and the refractory fibers are glass fibers;
the diameter of the infrared shading fiber is 18 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 600.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to a proportion, and adopting a ball milling stirring mode for mixing, wherein the stirring time is 1 hour;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 50kgf/cm 2 Pressing for 25min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 6 hours at 800 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 600kg/m 3 。
Example 3
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 50% of compressible powder and 50% of ceramic fiber;
the compressible powder is silica aerogel, the ceramic fiber is an infrared shading fiber, and the infrared shading fiber is a silicon carbide fiber;
the diameter of the infrared shading fiber is 15 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 800.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring for 7 minutes at a high speed, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 100kgf/cm 2 Pressing for 25min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 5 hours at 900 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 550kg/m 3 。
Example 4
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 50% of compressible powder and 50% of ceramic fiber;
the compressible powder is gas-phase aluminum dioxide powder, the ceramic fiber is an infrared shading fiber and a refractory fiber with the mass ratio of 1:49, the infrared shading fiber is a zirconia fiber, and the refractory fiber is an aluminum silicate fiber;
the diameter of the infrared shading fiber is 12 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 900.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 8 minutes, and uniformly mixing;
(2) Will step by stepThe raw materials mixed in the step (1) are introduced into a mold for compression molding, and the pressure is 3000kgf/cm 2 Pressing for 1min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 2 hours at 1500 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The bulk density of the fiber-reinforced low-density porous thermal insulation material of this example was 590kg/m 3 。
Example 5
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 99% of compressible powder and 1% of ceramic fiber;
the compressible powder is silica aerogel, the ceramic fiber is an infrared shading fiber, and the infrared shading fiber is a silicon carbide fiber;
the diameter of the infrared shading fiber is 10 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 1000.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to a proportion, and adopting a ball milling stirring mode for mixing, wherein the stirring time is 2 hours;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 500kgf/cm 2 Pressing for 20min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 4 hours at the temperature of 1000 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 100kg/m 3 。
Example 6
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 90% of compressible powder and 10% of ceramic fiber;
the compressible powder is silica aerogel and alumina aerogel with the mass ratio of 1:1, the ceramic fiber is infrared shading fiber and refractory fiber with the mass ratio of 1:1, the infrared shading fiber is zirconium silicate fiber, and the refractory fiber is mullite fiber;
the diameter of the infrared shading fiber is 8 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 100.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 10 minutes, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 1000kgf/cm 2 Pressing for 18min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 3 hours at 1200 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 110kg/m 3 。
Example 7
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 50% of compressible powder and 50% of ceramic fiber;
the compressible powder is gas-phase aluminum dioxide powder, the ceramic fiber is an infrared shading fiber, and the infrared shading fiber is a zirconia fiber;
the diameter of the infrared shading fiber is 15 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 300.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 5 minutes, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 1500kgf/cm 2 Pressing for 15min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 3 hours at 1400 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 595kg/m 3 。
Example 8
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 60% of compressible powder and 40% of ceramic fiber;
the compressible powder is silica aerogel and fumed silica powder with the mass ratio of 1:1, the ceramic fiber is an infrared shading fiber and a refractory fiber with the mass ratio of 1:3, the infrared shading fiber is an iron oxide fiber, and the refractory fiber is a silicon oxide fiber;
The diameter of the infrared shading fiber is 5 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 400.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to a proportion, and adopting a ball milling stirring mode for mixing, wherein the stirring time is 1.5 hours;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 2000kgf/cm 2 Pressing for 10min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 7 hours at 800 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 100kg/m 3 。
Example 9
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 70% of compressible powder and 30% of ceramic fiber;
the compressible powder is aluminum dioxide aerogel and gas-phase aluminum dioxide powder with the mass ratio of 1:1, the ceramic fiber is an infrared shading fiber and a refractory fiber with the mass ratio of 2:1, the infrared shading fiber is a zirconia fiber and a zirconium silicate fiber with the mass ratio of 1:1, and the refractory fiber is a silicon nitride fiber;
The diameter of the infrared shading fiber is 1 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 500.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 8 minutes, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 2500kgf/cm 2 Pressing for 5min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 3 hours at 1200 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 600kg/m 3 。
Example 10
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 55% of compressible powder and 45% of ceramic fiber;
the compressible powder is aluminum dioxide aerogel, the ceramic fibers are infrared shading fibers and refractory fibers in a mass ratio of 2:7, the infrared shading fibers are silicon carbide fibers, and the refractory fibers are mullite fibers;
The diameter of the infrared shading fiber is 1 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 500.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to a proportion, and adopting a ball milling stirring mode for mixing, wherein the stirring time is 2 hours;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 3000kgf/cm 2 Pressing for 3min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 5 hours at 900 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The bulk density of the fiber-reinforced low-density porous thermal insulation material of this example was 590kg/m 3 。
Example 11
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 50% of compressible powder and 50% of ceramic fiber;
the compressible powder is gas-phase aluminum dioxide powder, the ceramic fiber is an infrared shading fiber and a refractory fiber with the mass ratio of 4:1, the infrared shading fiber is a zirconia fiber, and the refractory fiber is an alumina fiber;
The diameter of the infrared shading fiber is 5 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 400.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 5 minutes, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 2200kgf/cm 2 Pressing for 15min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 4 hours at 1100 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 550kg/m 3 。
Example 12
In one embodiment of the fiber reinforced low-density porous heat insulation material, the preparation raw materials of the fiber reinforced low-density porous heat insulation material in the embodiment comprise the following raw materials in percentage by mass; 80% of compressible powder and 20% of ceramic fiber;
the compressible powder is aluminum dioxide aerogel and gas-phase aluminum dioxide powder with the mass ratio of 1:1, the ceramic fiber is an infrared shading fiber and a refractory fiber with the mass ratio of 1:1, the infrared shading fiber is a potassium hexatitanate fiber, and the refractory fiber is an aluminum silicate fiber;
The diameter of the infrared shading fiber is 5 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 500.
The fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing molding method, and the preparation method comprises the following steps:
(1) Mixing the compressible powder and the ceramic fiber according to the proportion, stirring at a high speed for 6 minutes, and uniformly mixing;
(2) Introducing the raw materials mixed in the step (1) into a mold for compression molding, wherein the pressure is 800kgf/cm 2 Pressing for 25min to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) for 5 hours at the temperature of 1000 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
The fiber-reinforced low-density porous heat insulating material of this example had a bulk density of 110kg/m 3 。
Example 13
Performance test of the fiber reinforced low-density porous heat insulation material
In this example, test groups 1 to 12 and control groups 1 to 12 were set, the test groups 1 to 12 were respectively made of the fiber-reinforced low-density porous heat insulating materials prepared in the above examples 1 to 12, and the heat insulating materials used in the control groups 1 to 12 were respectively as follows:
control group 1: the preparation raw materials of the heat insulation material of the control group consist of the following raw materials in percentage by mass; the compressible powder is 100%, and the compressible powder is aluminum dioxide aerogel. The preparation method of the heat insulating material is the same as that of the embodiment 1. The bulk density of the heat insulating material of the control group was 200kg/m 3 。
Control group 2: the preparation raw materials of the heat insulation material of the control group consist of the following raw materials in percentage by mass; 49% of compressible powder and 51% of ceramic fiber; the compressible powder is fumed silica powder, the ceramic fibers are infrared shading fibers and refractory fibers in a mass ratio of 21:30, the infrared shading fibers are titanium oxide fibers, and the refractory fibers are glass fibers; the diameter of the infrared shading fiber is 18 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 600. The preparation method of the heat insulating material is the same as that of the embodiment 2. The bulk density of the heat insulating material of the control group was 605kg/m 3 。
Control group 3: the preparation raw materials of the heat insulation material of the control group consist of the following raw materials in percentage by mass; 49% of compressible powder and 51% of ceramic fiber; the compressible powder is silica aerogel, the ceramic fiber is an infrared shading fiber, and the infrared shading fiber is a silicon carbide fiber; the diameter of the infrared shading fiber is 15 mu m, and the ratio of the length of the infrared shading fiber to the diameter is 800. The preparation method of the heat insulating material is the same as that of the embodiment 3. Heat insulation of the control groupThe bulk density of the material was 560kg/m 3 。
Control group 4: the preparation raw materials of the heat insulation material of the control group consist of the following raw materials in percentage by mass; 50% of compressible powder and 50% of ceramic fiber; the compressible powder is gas phase aluminum dioxide powder, the ceramic fiber is refractory fiber, and the refractory fiber is aluminum silicate fiber. The preparation method of the heat insulating material is the same as that of the embodiment 4. The bulk density of the heat insulating material of the control group was 590kg/m 3 。
Control group 5: the preparation raw materials of the heat insulation material of the control group consist of the following raw materials in percentage by mass; 100% of compressible powder; the compressible powder is silicon dioxide aerogel. The preparation method of the heat insulating material is the same as that of the embodiment 5. The bulk density of the heat insulating material of the control group was 90kg/m 3 。
Control group 6: the heat insulating material of the present control group was prepared as in example 6 above, except that the ratio of the length to the diameter of the infrared shielding fiber in the present control group was 90. The preparation method of the heat insulating material of the control group was the same as that of example 6. The bulk density of the insulation material of the control group was 110kg/m 3 。
Control group 7: the heat insulating material of the present control group was prepared as in example 7 above, except that the infrared shielding fiber in the present control group had a diameter of 21. Mu.m. The preparation method of the heat insulating material of the control group was the same as that of example 7. The bulk density of the heat insulating material of the control group was 605kg/m 3 。
Control group 8: the heat insulating material of the present control group was prepared in the same manner as in example 8 above, except that the bulk density of the heat insulating material in the present control group was 90kg/m 3 . The preparation method of the heat insulating material of the control group is the same as that of the above-mentioned example 8.
Control group 9: the heat insulating material of the present control group was prepared in the same manner as in example 9 above, except that the bulk density of the heat insulating material in the present control group was 610kg/m 3 . The preparation method of the heat insulating material of the control group was the same as that of example 9.
Control group 10: the materials for preparing the heat insulating material of the control group were the same as those of example 10 except that the material for the infrared light shielding fibers was selected. In the preparation raw materials of the heat insulation material of the control group, the infrared shading substance is silicon carbide powder. The preparation method of the heat insulating material of the control group was the same as that of example 10. The bulk density of the heat insulating material of the control group was 630kg/m 3 。
Control 11: the materials for preparing the heat insulating material of the control group were the same as those of example 11 except that the material for the infrared light shielding fiber was selected. In the preparation raw materials of the heat insulation material of the control group, the infrared shading substance is zirconia powder. The preparation method of the heat insulating material of the present control group was the same as that of example 11. The bulk density of the insulation material of the control group was 760kg/m 3 。
Control group 12: the materials for preparing the heat insulating material of the control group were the same as those of example 12 except that the material for the infrared light shielding fibers was selected. In the preparation raw materials of the heat insulation material of the control group, the infrared shading substance is potassium hexatitanate powder. The preparation method of the heat insulating material of the control group was the same as that of example 12. The bulk density of the insulation material of the control group was 110kg/m 3 。
The heat insulation materials of the test groups 1 to 12 and the control groups 1 to 12 are respectively tested for bending strength, highest use temperature and heat conductivity, and the test methods are respectively as follows:
bending strength: the test is carried out according to the national standard GB17671-1999 "cement mortar compressive strength test method", and the equipment for the test is a Jinan Yinuo brand YAW-300D type full-automatic bending resistance tester.
Maximum use temperature: the insulation material was processed into test specimens of 100X 10 mm. The test specimen was incubated at a specific temperature T1 for 24 hours and then tested for a change in length in the 100mm direction. If the linear shrinkage of the 100mm length is less than 2%, a new sample is taken and the shrinkage is measured after incubation in an environment of [ specific temperature T1+50℃ ] for 24 hours. Until the linear shrinkage of the sample to be tested exceeds 2% at a certain temperature Tn, the maximum use temperature of the sample can be considered to be [ Tn-50 ℃. At each temperature measuring point, the number of samples of the tested samples is 3, and when the linear shrinkage rate of the 3 samples is less than 2%, the next temperature measuring point can be tested; when one or more than one linear shrinkage rate in the 3 samples is more than 2%, the highest use temperature of the samples can be judged to be [ the temperature of the temperature measuring point is-50 ℃). Linear shrinkage = (100-length after incubation)/100.
Thermal conductivity: the thermal conductivity of each group of heat insulation materials at 800 ℃ is tested according to the measurement (a heat flow meter method) of the steady-state thermal resistance and related characteristics of the national standard GB10295-88 heat insulation materials, wherein the equipment for testing is a heat conductivity tester of the type DRS-3A of Xiangtan Xiangcao brand.
The test results of each group are shown in table 1.
Table 1 results of Performance test of the respective groups of heat insulating materials (thermal conductivity measured at 800 ℃ C.)
Group of Bending strength (MPa) Maximum use temperature (. Degree. C.) Thermal conductivity (W/mK)
Test group 1 0.2 1200 0.096
Test group 2 2.6 900 0.095
Test group 3 2.2 900 0.097
Test group 4 2.6 1300 0.096
Test group 5 0.1 800 0.085
Test group 6 0.1 1000 0.076
Test group 7 3.4 1500 0.099
Test group 8 0.2 800 0.088
Test group 9 2.8 1400 0.096
Test group 10 2.9 1400 0.085
Test group 11 2.7 1500 0.084
Test group 12 0.1 800 0.086
Control group 1 0.1 1100 0.102
Control group 2 2.8 900 0.106
Control group 3 2.3 900 0.102
Control group 4 2.6 1300 0.104
Control group 5 0.06 700 0.091
Control group 6 0.08 1000 0.076
Control group 7 3.5 1500 0.102
Control group 8 0.1 750 0.082
Control group 9 2.9 1400 0.102
Control group 10 2.1 1400 0.114
Control group 11 1.5 1400 0.246
Control group 12 0.04 800 0.054
The control group 1 resulted in too high heat loss of the sample due to infrared radiation and finally higher thermal conductivity compared to the test group 1, since no ceramic fiber, in particular no infrared shading fiber, was added.
Compared with the test group 2, the control group 2 has the advantages that the addition amount of the compressible powder is less than 50% of the total weight of the compressible powder and the ceramic fiber, so that the prepared sample has larger bulk density, the solid heat conduction is increased, and finally, the heat conductivity is higher.
Compared with the test group 3, the control group 3 has the advantages that the total amount of the ceramic fibers is too much, so that the addition amount of the compressible powder is occupied, the stacking density of the sample is improved, and the heat is transmitted through a 'heat channel' formed by the interconnected fibers due to the excessive fibers, so that the solid heat conduction is increased intangibly, and the thermal conductivity of the sample is higher.
The control group 4 had too much addition of the flame-retardant fiber compared to the test group 4, which resulted in the addition of the infrared shielding fiber being squeezed out, and the heat loss of the sample due to infrared radiation was too high, which resulted in a higher thermal conductivity.
The control group 5 had a smaller density of the prepared samples, and the bending strength of the samples was insufficient, because the ceramic fibers were not added to the samples, as compared with the test group 5. Moreover, the sample has too high heat-induced shrinkage rate without adding ceramic fiber, and the performance requirement of the invention that the maximum use temperature is above 800 ℃ is not met.
Compared with the test group 6, the control group 6 has the advantages that the ratio of the length to the diameter of the zirconium silicate fiber is smaller, so that the morphology of the zirconium silicate fiber in the sample is closer to that of powder particles, the supporting force on a sample blank is insufficient, the bending strength of the sample is directly insufficient, and the sample is easy to break when moving.
The control group 7 was compared with the test group 7, since the diameter of the zirconia fiber used was too large, the total number and total length of the fiber became smaller with the fiber addition ratio unchanged, which directly resulted in insufficient support of the fiber to the sample embryo, leading to a higher bulk density of the sample, and also, due to an increase in solid state heat conduction, leading to a higher thermal conductivity.
Control group 8 did not reach the minimum bulk density (100 kg/m 3 ) Resulting in shrinkage of over 2% after 24 hours incubation at 800 c, rendering it incapable of operating at 800 c, but only at 750 c, less than the 800 c range of minimum use temperatures of the present invention.
Control group 9 compared with test group 9, the bulk density of the sintered sample exceeded the maximum value of the bulk density (600 kg/m 3 ) Resulting in a sample with a solid state heat conduction that is too high to exceed the maximum value of the thermal conductivity (0.1W/mK) described in the present invention.
In comparison with the control group 10, the infrared shielding material used was not silicon carbide fiber, but silicon carbide powder, and the tap density of silicon carbide powder was far higher than that of silicon carbide fiber, so that the sample lacked the support of silicon carbide fiber, the bulk density exceeded the maximum value of the bulk density according to the present invention, the solid state heat conduction was increased, and the thermal conductivity of the sample exceeded the maximum value of the thermal conductivity according to the present invention (0.1W/mK).
In the control group 11, compared with the test group 11, the infrared light shielding material used was not zirconia fiber, but zirconia powder, so that the formed density was too high due to lack of support of zirconia fiber on the blank during forming, and the bulk density of the sample was finally too high after sintering, and the thermal conductivity was too high due to the high solid state heat conduction. In addition, in the case of using zirconia fiber, the maximum use temperature of the sample in the examples reached 1500 ℃. For this comparative example, the shrinkage of the sample exceeded 2% at 1500 ℃ due to the lack of support of the sample by the zirconia fiber at high temperature, resulting in a heat soak of 24 hours at 1500 ℃ which makes it incapable of operating at 1500 ℃ but only 1400 ℃.
Control 12 compared to test 12, at the same bulk density, the lack of reinforcement of the sample by the fiber resulted from the addition of the infrared light shielding material to the sample, not potassium hexatitanate fiber, but potassium hexatitanate powder, resulted in the sample not reaching the minimum (0.1 MPa) of the flexural strength of the sample.
As is clear from the results of table 1, the heat insulating material of the control group was significantly different from the test group in terms of bending strength, maximum use temperature, thermal conductivity, and the like, although the control group was finely adjusted only in terms of the size of the compressible powder, the infrared light shielding fiber, the refractory fiber, the bulk density, and the like, or the content thereof, as compared with the test group. Therefore, in the preparation raw materials of the fiber reinforced low-density porous heat insulation material, any one of the raw material substances or the content changes have obvious influence on the performance of the finally prepared fiber reinforced low-density porous heat insulation material, so that the performance requirement of the fiber reinforced low-density porous heat insulation material cannot be met.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.

Claims (8)

1. The fiber reinforced low-density porous heat insulation material is characterized in that the fiber reinforced low-density porous heat insulation material is prepared by adopting a dry pressing method, and the preparation raw materials comprise the following raw materials in percentage by mass: 50-99% of compressible powder and 1-50% of ceramic fiber;
the ceramic fiber consists of refractory fiber and infrared shading fiber, wherein the refractory fiber accounts for 0-49% of the total mass of the raw material for preparing the fiber reinforced low-density porous heat insulation material, and the infrared shading fiber accounts for 1-50% of the total mass of the raw material for preparing the fiber reinforced low-density porous heat insulation material;
the refractory fiber is at least one of glass fiber, aluminum silicate fiber, mullite fiber, aluminum oxide fiber, silicon oxide fiber and silicon nitride fiber, and the diameter of the refractory fiber is less than or equal to 20 mu m, and the length of the refractory fiber is 1-100 mm;
The infrared shading fiber is at least one of carbon fiber, titanium oxide fiber, silicon carbide fiber, zirconium oxide fiber, zirconium silicate fiber, potassium hexatitanate fiber and ferric oxide fiber, the ratio of the length to the diameter of the infrared shading fiber is more than or equal to 100, and the diameter of the infrared shading fiber is less than or equal to 20 mu m;
the bulk density of the fiber reinforced low-density porous heat insulation material is 100-600 kg/m 3 。
2. The fiber reinforced low density porous thermal insulation material of claim 1, wherein the ratio of the length to the diameter of the infrared shielding fiber is 100 to 1000, and the diameter of the infrared shielding fiber is 10 μm or less.
3. The fiber reinforced low density porous thermal insulation material of claim 2, wherein the ratio of the length to the diameter of the infrared shielding fiber is 200 to 500, and the diameter of the infrared shielding fiber is 5 μm or less.
4. The fiber reinforced low density porous thermal insulation material of claim 1, wherein the bulk density of the fiber reinforced low density porous thermal insulation material is 200 to 450kg/m 3 。
5. The fiber reinforced low density porous thermal insulation material of claim 4, wherein the bulk density of the fiber reinforced low density porous thermal insulation material is 250-350 kg/m 3 。
6. The fiber reinforced low density porous thermal insulation material of claim 1, wherein the compressible powder is at least one of aerogel powder, gas phase oxide powder; the aerogel powder comprises at least one of silica aerogel powder and alumina aerogel powder; the gas-phase oxide powder comprises at least one of gas-phase silicon oxide powder and gas-phase aluminum oxide powder.
7. The fiber reinforced low density porous thermal insulation material of claim 1, wherein the fiber reinforced low density porous thermal insulation material has a flexural strength greater than 0.1MPa; the highest use temperature of the fiber reinforced low-density porous heat insulation material is more than or equal to 800 ℃; the thermal conductivity of the fiber reinforced low-density porous heat insulation material at 800 ℃ is less than 0.1W/mK.
8. A method for producing a fiber-reinforced low-density porous heat insulating material according to any one of claims 1 to 7, wherein the production method is a dry press molding method, and the production method comprises the steps of:
(1) Mixing the compressible powder and the ceramic fiber according to a proportion;
(2) Introducing the raw materials mixed in the step (1) into a die for compression molding, wherein the pressure is 10-3000 kgf/cm 2 Pressing to obtain a biscuit;
(3) Sintering the biscuit obtained in the step (2) at 800-1500 ℃ to obtain the fiber reinforced low-density porous heat insulation material.
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