WO2023040965A1 - 一种稀土掺杂二氧化硅气凝胶及其制备方法和应用 - Google Patents

一种稀土掺杂二氧化硅气凝胶及其制备方法和应用 Download PDF

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WO2023040965A1
WO2023040965A1 PCT/CN2022/119046 CN2022119046W WO2023040965A1 WO 2023040965 A1 WO2023040965 A1 WO 2023040965A1 CN 2022119046 W CN2022119046 W CN 2022119046W WO 2023040965 A1 WO2023040965 A1 WO 2023040965A1
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rare earth
airgel
preparation
gel
silica
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PCT/CN2022/119046
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English (en)
French (fr)
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余煜玺
李璐
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中科润资(重庆)节能科技有限公司
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Priority claimed from CN202111091766.1A external-priority patent/CN113651334A/zh
Priority claimed from PCT/CN2022/088412 external-priority patent/WO2023201688A1/zh
Priority claimed from PCT/CN2022/088413 external-priority patent/WO2023201689A1/zh
Application filed by 中科润资(重庆)节能科技有限公司 filed Critical 中科润资(重庆)节能科技有限公司
Publication of WO2023040965A1 publication Critical patent/WO2023040965A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/155—Preparation of hydroorganogels or organogels
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/157—After-treatment of gels
    • C01B33/158—Purification; Drying; Dehydrating
    • 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
    • C04B30/00—Compositions for artificial stone, not containing binders

Definitions

  • the invention belongs to the technical field of airgel and its preparation, and in particular relates to a rare earth-doped silica airgel and a preparation method thereof.
  • Airgel is a new type of thermal insulation material with nanoscale pores, among which silica SiO 2 aerogel is currently the most widely used.
  • silica SiO 2 airgel is easy to sinter and cause structural collapse at high temperature, its long-term use temperature is only 650 °C. Therefore, the high temperature stability is generally improved by doping heterogeneous elements.
  • rare earth silicate As an environmental barrier coating, rare earth silicate has good high temperature stability and excellent heat insulation performance, but the existing rare earth silicate ceramics have low porosity (50%-70%) and large pore size ( 0.4 ⁇ 3.5 ⁇ m), the thermal conductivity will rise rapidly in high temperature environment, so it is not suitable for high temperature insulation.
  • rare earth doped silica airgel can combine the superior nanostructure of airgel and the temperature resistance of rare earth materials. It has great application prospects in heat insulation.
  • the present invention provides a rare earth-doped silica airgel, which can have both the superior nanostructure of the airgel and the temperature resistance characteristics of the rare earth material. Specifically, since the doping of rare earths can increase the service temperature of silica airgel, the application of extended airgel under extreme high temperature conditions can control the density and microstructure of the airgel, and further control the content of anions in it. Therefore, the thermal conductivity of the airgel is controlled, and the airgel has great application prospects in thermal insulation.
  • the present invention also provides a method for preparing the above-mentioned rare earth-doped silica aerogel, the process of the method is simple and easy, the production efficiency is high, and it is favorable for large-scale production of the rare earth-doped silica aerogel.
  • the inventor found that the rare earth-doped silica airgel will corrode other materials, such as the metal pipeline wrapped by the metal, during use.
  • the inventor found through research that the main cause of corrosion is residual anion impurity elements, such as chloride ions. Chloride ions in rare earth doped aerogels mainly come from the rare earth raw materials in the airgel preparation process.
  • the present invention specifically discloses the following schemes:
  • a rare-earth-doped silica airgel the airgel is bulk rare-earth-doped silica airgel, and the halogen ion content in the airgel is not higher than 0.2wt%.
  • the rare earth element is selected from at least one of yttrium Y, scandium Sc, and La series rare earth metals, and the rare earth element is REE (Rare Earth Element).
  • the rare earth elements exist in the form of REE-O-Si bonds in the airgel.
  • the rare earth element forms a network amorphous structure together with Si element and oxygen element.
  • the rare earth element is uniformly distributed in the network amorphous structure.
  • the airgel has at least one of the following properties:
  • the average pore size is 10nm to 22nm
  • the hydrophobic angle is 85° ⁇ 130°.
  • the airgel further includes at least one of silica micropowder, opacifying agent, fiber and aluminum.
  • the present invention also provides a method for preparing the above-mentioned rare earth-doped silica aerogel, the method comprising the following steps:
  • rare earth silica sol prepare a rare earth compound solution, and mix the rare earth compound solution with the above silica sol to obtain a rare earth silica sol;
  • the rare earth compound is a rare earth metal nitrate, a rare earth metal oxalate, a rare earth metal carbonate or at least one of rare earth metal oxides;
  • Solvent replacement step using ethanol to replace water, halogen ions and other impurities in the rare earth- SiO2 gel;
  • silica micropowder in the silica sol in step 1), silica micropowder can also be added.
  • an opacifying agent may also be added to the silica sol in step 1).
  • a combination of silicon sources and rare earth compounds is employed in the method.
  • step 3 also introduces fiber in the gel preparation process, adopts a kind of in following two ways:
  • the first method after adding a gel catalyst to the above-mentioned rare earth silica sol, it is poured into the fiber prefabricated part, and then left to stand to obtain a gel;
  • the second method after adding a gel catalyst to the above-mentioned rare earth silica sol, adding reinforcing fibers and a fiber dispersant, and then standing still to obtain a gel.
  • step 4) also includes a modification step before, specifically including:
  • the present invention also provides a silica airgel particle, the particle has a core-shell structure; wherein, the shell is aluminum oxide and/or aluminum salt and the core is the above-mentioned rare earth doped silica airgel, or , the outer shell is the above-mentioned rare earth doped silica airgel and the inner core is aluminum oxide and/or aluminum salt.
  • the present invention also provides a preparation method of the silica airgel particles, the preparation method comprising the following steps:
  • the rare earth-doped silica airgel particles are prepared first, and then mixed with aluminum oxide and/or aluminum salt to prepare the outer shell of aluminum oxide and/or aluminum salt and the inner core of the above-mentioned rare earth doped silica airgel particles.
  • the aerogel is prepared by using the above-mentioned method for preparing the rare earth-doped carbon dioxide aerogel, wherein aluminum oxide and/or aluminum salt particles are added during the preparation of the gel in the step 3), so that the aerogel can be prepared Particles in which the outer shell is the above-mentioned rare earth-doped silica airgel and the inner core is aluminum oxide and/or aluminum salt are obtained.
  • the present invention first adopts the sol-gel method to prepare rare earth-doped silica wet gel, through the replacement of ethanol, and then obtains massive rare earth-doped silica aerogel after ethanol supercritical drying, and the obtained aerogel
  • the gel density is low, the specific surface area is high, and it has good thermal insulation performance; in addition, its hydrophobic angle is 85° ⁇ 130°, and it has less powder shedding when it is mixed with fibers to prepare composite materials. It is tested by GBT 4857.7-2005 standard , The mass loss rate of the composite material is ⁇ 5%.
  • the preparation process of the airgel is simple and easy, the production efficiency is high, the requirement for equipment is low, and it is beneficial to large-scale production.
  • the content of halide ions (especially chlorine ions) in the airgel of the present invention is not higher than 0.2%; specifically, the content of halogen ions (especially chlorine ions) in the airgel of the present invention is not higher than 0.15%, It may even be free of halide ions (especially chloride ions).
  • the airgel of the present invention has low density, high specific surface area, and good thermal insulation performance; in addition, its hydrophobic angle is 85° to 130°, and it has the characteristics of less powder shedding when it is used to mix with fibers to prepare composite materials , the application of GBT 4857.7-2005 standard test, the mass loss rate of composite materials ⁇ 5%.
  • the airgel of the present invention has the performance of being used at high temperatures, and can still maintain the heat insulation effect at 800-1200° C., and can be extended and applied to extreme conditions of high temperature.
  • the present invention can control the density and microstructure of the airgel, and control the content of halogen ions (especially chloride ions) in the airgel by controlling the ethanol content, rare earth doping amount and molding process, and selecting specific rare earth-containing compounds, etc. , thereby reducing the corrosion of the airgel to other objects during use.
  • halogen ions especially chloride ions
  • liquid-phase heterogeneous elements rare earth elements
  • Fig. 1 is a macroscopic view of the bulk Y-SiO 2 airgel prepared in Example 1 of the present invention.
  • Fig. 2 is the N 2 adsorption-desorption curve and pore size distribution diagram of the bulk Y-SiO 2 airgel prepared in Example 1 of the present invention.
  • Fig. 3 is a SEM microscopic image of the bulk Y-SiO 2 airgel prepared in Example 1 of the present invention.
  • Fig. 4 is a schematic diagram of the preparation process of the bulk Y-SiO 2 airgel of the present invention.
  • Fig. 5 is a high-temperature thermal conductivity diagram of the bulk Y-SiO 2 airgel prepared in Example 6 of the present invention.
  • Fig. 6 is a schematic diagram of the preparation process of the fiber-reinforced Y-SiO 2 airgel composite material.
  • Fig. 7 is a schematic diagram of the smoke prevention and exhaust duct of the present invention.
  • Fig. 8 is a schematic diagram of the quick disassembly and assembly air duct of the present invention.
  • Fig. 9 is a schematic diagram of the heat shielding layer of the present invention.
  • Fig. 10 is a schematic diagram of the heat-insulating layer wrapping the high-temperature-resistant protective layer of the present invention.
  • Fig. 11 is a schematic diagram of the morphology of the high-temperature expansion layer of the present invention at different temperatures.
  • Fig. 12 is a schematic structural view of the smoke exhaust duct of the present invention.
  • Fig. 13 Schematic diagram of dendritic ceramic fiber airgel.
  • the present invention provides a rare earth-doped silica airgel, which is bulk rare earth-doped silica airgel, and the content of halide ions in the airgel is not higher than 0.2wt%.
  • the invention provides an aerogel with extremely low content of halogen ions, which reduces its corrosion on objects to be insulated and improves the application prospect of the aerogel as a heat-insulating and heat-insulating material.
  • the silica airgel is doped with rare earth elements, and the doped rare earth elements can inhibit the high-temperature sintering of the silica airgel material, improve the high temperature resistance of the material, and have a good effect on the airgel material.
  • the spatial network structure has a good supporting effect, which can effectively prevent the collapse of the pore structure and improve its thermal insulation performance at high temperatures.
  • the rare earth is at least one selected from yttrium Y, scandium Sc, and La-series rare earth metals (such as selected from neodymium Nd, ytterbium Yb, etc.).
  • the rare earth exists in the form of REE-O-Si bond in the airgel.
  • the content of halide ions (especially chloride ions) in the airgel is not higher than 0.15wt%; specifically, no halide ions (especially chloride ions) may be contained.
  • the airgel of the present invention has low density, high specific surface area, low content of halide ions or even no halide ions (such as chloride ions), and has good thermal insulation performance.
  • the rare earth elements together with Si elements and oxygen elements form a network amorphous structure.
  • the rare earth element is uniformly distributed in the network amorphous structure.
  • the airgel has a density of 0.08-0.35 g/cm 3 ; for example, 0.10-0.30 g/cm 3 ; specifically, 0.08 g/cm 3 , 0.10 g/cm 3 , 0.12 g/cm 3 , 0.14g/cm 3 , 0.17g/ cm 3 , 0.20g/cm 3 , 0.22g/cm 3 , 0.24g/cm 3 , 0.27g/cm 3 , 0.29g/cm 3 , 0.30g/cm 3 cm 3 or 0.35 g/cm 3 .
  • the specific surface area of the airgel is 640-880m 2 /g; specifically 640m 2 /g, 648.17m 2 /g, 844.28m 2 /g, 861.17m 2 /g or 880m 2 /g.
  • the average pore diameter of the airgel is 10nm-22nm; 20nm, 20.45nm, 21nm or 22nm.
  • the airgel further includes at least one of silica micropowder, opacifying agent, fiber and aluminum.
  • the opacifying agent may be at least one of titanium dioxide, carbon black, SiC, potassium hexatitanate, and ZrO 2 .
  • the fibers are selected from at least one of brucite fibers, ceramic fibers, glass fibers, and quartz fibers.
  • the fibers are reinforcing fibers
  • the reinforcing fibers may be at least one of aluminum silicate fibers, alumina fibers, glass fibers, mullite fibers, and SiO 2 ceramic nanofibers.
  • the hydrophobic angle of the airgel is 85°-130°.
  • the present invention provides a method for preparing the above-mentioned rare earth-doped silica airgel.
  • the method first adopts a sol-gel method to prepare a wet gel, and replaces it with ethanol, and then passes drying (especially is supercritical drying) to prepare the rare earth-doped silica aerogel, specifically the method comprises the following steps:
  • rare earth silica sol prepare a rare earth compound solution, and mix the rare earth compound solution with the above silica sol to obtain a rare earth silica sol;
  • the rare earth compound is a rare earth metal nitrate, a rare earth metal oxalate, a rare earth metal carbonate or at least one of rare earth metal oxides;
  • Solvent replacement step using ethanol to replace water, halogen ions and other impurities in the rare earth- SiO2 gel;
  • the process of the method of the invention is simple and easy, the production efficiency is high, and it is beneficial to the large-scale production of the rare earth-doped silica airgel.
  • the present invention first adopts the sol-gel method to prepare rare earth-doped silica wet gel, and through the replacement of ethanol, and then obtains massive rare earth-doped silica aerogel after ethanol supercritical drying, and obtains
  • the airgel has low density, high specific surface area, and good thermal insulation performance; in addition, the prepared airgel has hydrophobicity, and its hydrophobic angle is 85° to 130°; moreover, the airgel is used in When it is mixed with fibers to prepare composite materials, it has the characteristics of less powder shedding. Specifically, according to GBT4857.7-2005 standard test, the mass loss rate of composite materials is less than 5%.
  • a hydrolysis catalyst in step 1), can also be added to the silica sol, in order to accelerate the hydrolysis of the silicon source and obtain the silica sol faster.
  • the step 1) specifically includes: adding the silicon source, the alcohol solvent and water into the container in proportion, mixing them, adding a hydrolysis catalyst, mixing them again, and standing still to obtain the silica sol.
  • step 1) silicon source, alcohol solvent and water are sequentially added into the container according to the molar ratio of 1:(7-20):3; specifically, silicon source, alcohol solvent and water are added according to Add the molar ratio of 1:8 to 15:3 into the container in sequence.
  • the silicon source is selected from sodium silicate, ethyl orthosilicate, methyl orthosilicate, tetrapropoxysilane, tetrabutoxysilane, dimethyl at least one of dimethoxysilane or dimethyldiethoxysilane.
  • the alcohol solvent is methanol, ethanol or a combination thereof.
  • the mixing time for the first time is 10 minutes to 15 minutes.
  • the hydrolysis catalyst is selected from hydrochloric acid, oxalic acid, nitric acid, sulfuric acid, phosphoric acid or combinations thereof.
  • step 1) the hydrolysis catalyst is added dropwise; specifically, it can be added dropwise through a constant pressure funnel.
  • step 1) the hydrolysis catalyst is added in the form of a solution, the mass fraction of the hydrolysis catalyst solution is 0.05-0.1 wt%, and the molar ratio of the silicon source to the hydrolysis catalyst can be 1:(10- 4).
  • step 1) the time for the second mixing is 100min ⁇ 120min.
  • the standing time may be 20h to 48h, such as 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h or 48h.
  • the selection of the time can make the hydrolysis reaction proceed fully and slowly.
  • microsilica powder can also be added to the silica sol in step 1).
  • the specific step 1) is to prepare the silica sol: mix the silicon source, water, alcohol solvent, and silicon micropowder to prepare the silica sol, add a hydrolysis catalyst to the silica sol to accelerate the hydrolysis of the silicon source, and obtain the silica sol faster.
  • the particle size range of the silicon micropowder is 600 mesh-1500 mesh
  • the silicon micropowder is amorphous (amorphous) silicon micropowder
  • the addition amount of the silicon micropowder is 1%-15%.
  • an opacifying agent may also be added to the silica sol in step 1), the purpose of which is to enhance the temperature insulation performance under high temperature conditions.
  • the opacifying agent includes at least one of titanium dioxide, carbon black, SiC, potassium hexatitanate, ZrO 2 and the like.
  • titanium dioxide may be anatase titanium dioxide.
  • the titanium dioxide can be fluorine-doped or nitrogen-doped titanium dioxide nanoparticles, and the introduction of such titanium dioxide can enhance the shading effect of infrared radiation.
  • the specific process of preparing the rare earth compound solution includes: dissolving the rare earth compound in water, heating and reacting, and cooling to room temperature to obtain the rare earth compound solution.
  • the rare earth compound is at least one of rare earth metal nitrate, rare earth metal oxalate, rare earth metal carbonate or rare earth metal oxide; At least one of yttrium Y, scandium Sc, and La-series rare earth metals (eg, selected from neodymium Nd, ytterbium Yb, etc.).
  • the rare earth compound is a combination of two or more, specifically at least one of yttrium metal nitrate, oxalate or carbonate and scandium metal nitrate, oxalate or carbonate A combination of at least one.
  • the rare earth compound is at least one of rare earth metal nitrate, rare earth metal oxalate, and rare earth metal carbonate.
  • it is rare earth metal nitrate hydrate, for example, the rare earth compound is Y(NO 3 ) 3 ⁇ 4H 2 O, Sc(NO 3 ) 3 ⁇ 6H 2 O, Nd(NO 3 ) 3 ⁇ 6H 2 O, Yb( At least one of NO 3 ) 3 ⁇ 5H 2 O and the like.
  • nitrate, oxalate or carbonate are used as rare earth raw materials, such as yttrium nitrate, scandium nitrate, neodymium nitrate, yttrium oxalate, scandium oxalate, neodymium oxalate, yttrium carbonate, scandium carbonate and neodymium carbonate, avoiding the halide ion
  • yttrium nitrate scandium nitrate, neodymium nitrate, yttrium oxalate, scandium oxalate, neodymium oxalate, yttrium carbonate, scandium carbonate and neodymium carbonate
  • the silicon source can be selected from sodium silicate, ethyl orthosilicate, methyl orthosilicate, tetrapropoxysilane, tetrabutoxysilane, dimethyldimethoxysilane or dimethyldimethoxysilane A combination of two or more of ethoxysilanes.
  • the rare earth compound can be selected from at least one of yttrium metal nitrate, oxalate or carbonate, scandium metal nitrate, at least one of oxalate or carbonate, La series metal nitrate , oxalate or carbonate (such as neodymium metal nitrate, at least one of oxalate or carbonate, ytterbium metal nitrate, at least one of oxalate or carbonate), yttrium A combination of two or more metal oxides, scandium metal oxides, and La-based metal oxides (such as neodymium metal oxides, ytterbium metal oxides).
  • yttrium metal salt can be yttrium nitrate, yttrium chloride, yttrium oxalate, yttrium carbonate; scandium metal salt can be scandium nitrate, scandium chloride, scandium oxalate, scandium carbonate; neodymium metal salt can be neodymium nitrate, neodymium chloride , yttrium oxalate, neodymium carbonate; ytterbium metal salt can be ytterbium nitrate, ytterbium chloride, ytterbium oxalate, ytterbium carbonate.
  • the rare earth compound solution may contain two or more of the above rare earth compounds.
  • a water bath is used for heating.
  • the heating temperature may be 40°C-60°C, for example, 45-50°C; the heating time may be 20min-60min, for example, the heating time may be 30min-35min.
  • the mass ratio of the rare earth nitrate to water may be (3-4):1.
  • the gel catalyst is selected from at least one of ammonia water, dimethylformamide, ammonia water ethanol dilution, ammonium bicarbonate, ammonium carbonate and the like. Specifically, the gel catalyst is added dropwise.
  • the gel catalyst in step 3), is preferably NH 3 ⁇ H 2 O, NH 4 HCO 3 and (NH 4 ) 2 CO 3 , which can avoid the introduction of other impurities, wherein NH 3 ⁇ H
  • the molar ratio of the silicon source to the gel catalyst in the material may be 1:(0.1-0.25).
  • step 3) also introduces fibers in the process of preparing the gel; specific step 3) the process of preparing the gel is: after adding the gel catalyst to the above-mentioned rare earth silica sol, pour it into a fiber preform, which is then left to obtain a gel.
  • the fiber preform can be made of at least one of brucite fiber, ceramic fiber, glass fiber, and quartz fiber.
  • the standing time may be 24h-72h.
  • step 3) also introduces fibers in the process of preparing the gel;
  • the specific step 3) of preparing the gel is: after adding a gel catalyst to the above-mentioned rare earth silica sol, then adding reinforcement Fiber and fiber dispersant, after standing still to obtain gel.
  • the fiber dispersant may be sodium dodecylsulfonate, polyethylene glycol, sodium lauryl sulfate, sodium hexametaphosphate, and the like.
  • the reinforcing fibers may be at least one of aluminum silicate fibers, alumina fibers, glass fibers, mullite fibers, and SiO2 ceramic nanofibers.
  • the mullite fibers may be dendrite-reinforced mullite fibers.
  • the preparation method of the dendrite-reinforced mullite fiber is as follows: immerse the aluminum silicate fiber in the impregnation solution, and then freeze-dry it; repeat the impregnation and freeze-drying process three times and then dry it.
  • the first impregnation solution is silica sol
  • the second impregnation solution is AINO 3
  • the third impregnation solution is NH 4 F solution
  • the molar ratio of silicon source, aluminum source and fluorine source for the third impregnation is 1:3:12.
  • step 4) also includes a modification step before, specifically including:
  • the step 3') includes: soaking the above-mentioned rare earth-SiO 2 gel in a modifier to obtain a modified rare earth-SiO 2 gel.
  • the soaking time can be 4h ⁇ 48h.
  • the modifying agent is an organosilicon hydrocarbon compound solution, and the mass fraction of the organosilicon hydrocarbon compound in the solution is 0.5-5%.
  • the organic silicon hydrocarbon compound can be chlorotrimethylsilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltriethoxysilane, tridecafluorooctyltrimethoxysilane, Heptadecafluorodecyltrimethoxysilane, acetoxytrimethylsilane, benzyldimethylchlorosilane, benzyltrichlorosilane, benzyltriethoxysilane, tert-butyltrimethylchlorosilane, At least one of chloroisobutylmethylsilane, n-butyltrichlorosilane, cycloethyltrichlorosilane, 3-chlor
  • the solvent in the organic silicon hydrocarbon compound solution is n-hexane, ethanol, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, dichloromethane, methanol, At least one of carbon tetrachloride, pyrimidine, xylene, cyclohexane, methyl ethyl ketone or methyl acetate.
  • the replacement organic solvent may be one of ethanol, isopropanol, n-hexane or a combination thereof.
  • step 5 the above-mentioned rare earth-SiO 2 gel is first airtightly aged and then subjected to supercritical drying.
  • the standing aging time may be 22-24 hours.
  • the use of ethanol supercritical drying in step 5) can not only improve the hydrophobicity, but also reduce the problem of powder dropping and improve the quality of the airgel.
  • the drying condition of step 5) is: take ethanol as the medium of supercritical drying, pre-charge N to make certain pressure in the still; , keep it warm for a certain period of time until the pressure in the kettle reaches a certain set value; turn on the water cooling device, release the pressure in the kettle to normal pressure, and then pass in N2 to purge the kettle, and after cooling to room temperature, get rare earth doped silica gas condensation glue.
  • the condition of ethanol supercritical drying is that after raising the temperature and increasing the pressure to the critical point according to a preset program, the fluid inside the reactor is released at a slow speed under a constant temperature state, until the internal and external pressures are balanced.
  • N2 can be used to pre-fill the reactor.
  • the pressure of pre-filling N2 is 1-4MPa. When the temperature rises above 240°C, the heating rate is 0.5-2°C/min. When the pressure exceeds 8MPa, turn on the cooling device and release the pressure slowly. , after the pressure was released to normal pressure, N2 was passed into the reactor to purge the reactor, and after cooling to room temperature, the rare earth doped aerogel was obtained.
  • the conditions of the supercritical drying can be: use ethanol as the medium of supercritical drying, pre-fill N to the pressure inside the kettle to 2MPa, raise the temperature inside the kettle to 270°C at a heating rate of 1°C/min, Keep warm for 2-4 hours until the pressure in the kettle is 8-10MPa, turn on the water cooling device, slowly release the pressure in the kettle to normal pressure, then pass in N2 to purge the kettle, and cool to room temperature to obtain rare earth doped silica airgel .
  • the present invention also provides a silica airgel particle, the particle has a core-shell structure; wherein, the shell is aluminum oxide and/or aluminum salt and the core is the above-mentioned rare earth doped silica airgel, or , the outer shell is the above-mentioned rare earth doped silica airgel and the inner core is aluminum oxide and/or aluminum salt.
  • the particle size of the silicon micropowder is 1000-3000 mesh.
  • the amount of silicon micropowder added is 1%-15%.
  • the surface of the silicon micropowder is covered with a titanium dioxide film.
  • the titanium dioxide is nitrogen-doped or fluorine-doped titanium dioxide. The study found that coating titanium dioxide on the surface of silica powder and then adding it to the airgel can not only exert the characteristics of silica powder to regulate and inhibit the shrinkage of silica airgel at high temperature, but also solve the problem of titanium dioxide agglomeration, thereby further Improve the high-temperature thermal insulation performance of silica airgel.
  • Amorphous silicon powder is a silicon dioxide material, and there will be a phenomenon of volume change caused by the transformation of crystal form under temperature change. The expansion of the volume of amorphous silicon micropowder will suppress and reduce the internal stress when the airgel particles experience high temperature, thereby reducing the structural changes inside the airgel particles and stabilizing their thermal insulation performance under high temperature conditions.
  • microsilica powder will react and transform to mullite at high temperature and contain aluminum elements.
  • Mullite is an excellent refractory material, so the addition of microsilica powder further improves the quality of the silica. High temperature resistance of airgel particles.
  • the particle size of silica powder is 800-8000 mesh, 1000-2000 mesh, 2000-3000 mesh, 3000-4000 mesh, 4000-5000 mesh, 5000-6000 mesh, 6000-7000 mesh, 7000-8000 mesh Mesh, 1000-1500 mesh, 1500-3000 mesh, or 10-800nm, 10-100nm, 50-200nm, 100-400nm, 300-800nm.
  • the preferred particle size is 800-1000 mesh, 1000-1200 mesh, 1000-3000 mesh.
  • the addition amount (mass percentage) of silicon micropowder is 3-25%, 1-10%, 3-15%, 5-20%, 5-25%, 10-25%, preferred addition amount It is 2-10%, 3-8%, 3-6%.
  • the addition amount (mass percentage) of the amorphous silicon micropowder is 1-20%, 1-15%, 2-10%, 3-8%.
  • the preferred particle size can better promote the combination of silicon, aluminum and oxygen bonds, making the structure more stable.
  • the optimal addition amount can better improve the shrinkage resistance of airgel particles at high temperature, while maintaining high thermal insulation performance and mechanical strength.
  • the particles are alumina particles externally wrapping the rare earth-doped silica airgel layer, aluminum silicate particles externally including the rare earth-doped silica airgel layer, external At least one of the rare earth-doped silica airgel particles wrapped in the aluminum oxide protective layer.
  • the aluminum oxide protective layer has a thickness ranging from 1 ⁇ m to 500 ⁇ m.
  • the rare earth doped silica airgel coating has a thickness ranging from 0.5 ⁇ m to 250 ⁇ m.
  • the present invention also provides a preparation method of the above-mentioned silica airgel particles, which comprises the following steps:
  • the rare earth-doped silica airgel particles are prepared first, and then mixed with aluminum oxide and/or aluminum salt to prepare the outer shell of aluminum oxide and/or aluminum salt and the inner core of the above-mentioned rare earth doped silica airgel particles.
  • the aerogel is prepared by using the above-mentioned method for preparing the rare earth-doped carbon dioxide aerogel, wherein aluminum oxide and/or aluminum salt particles are added during the preparation of the gel in the step 3), so that the aerogel can be prepared Particles in which the outer shell is the above-mentioned rare earth-doped silica airgel and the inner core is aluminum oxide and/or aluminum salt are obtained.
  • the XRF test shows that the impurity content of Cl ⁇ is 0.03wt%-0.15wt%. Doping with rare earth nitrates can reduce the Cl ⁇ content in airgel products and reduce the corrosion caused by chloride ions, which is beneficial to the application of airgel.
  • step (3) Weigh 0.684g of the material obtained in step (2), slowly drop into 9.31g of SiO 2 sol, and stir magnetically for 30min.
  • step (3) Drop ammonia water and ethanol diluent into the material obtained in step (3), stir evenly, and let stand to gel.
  • the macroscopic view of the bulk Y-SiO 2 airgel obtained in this example is shown in Figure 1.
  • the obtained airgel has a density of 0.17g/cm 3 , a specific surface area of 648.17m 2 /g, and an average
  • the pore size is 20.45nm.
  • Its N2 adsorption-desorption curve and pore size distribution diagram are shown in Figure 2, and the microstructure of the airgel is shown in Figure 3.
  • the content of halide ions in the airgel is 0.09%.
  • the thermal conductivity of the rare earth-doped silica airgel of Example 1 and the conventional silica airgel at high temperature were tested, and the test results are listed in Table 1. It can be seen that the airgel of the present invention has significantly improved thermal conductivity at high temperature compared with conventional silica airgel.
  • the rare earth doped silica airgel of embodiment 1 conventional silica airgel temperature(°C) Thermal conductivity (W/m ⁇ K) Thermal conductivity (W/m ⁇ K) 300 0.037 0.038 400 0.045 0.049 500 0.051 0.061 600 0.060 >0.1 700 0.065 >0.1 800 0.070 >0.1 900 0.078 >0.1 1000 0.082 >0.2 1100 0.095 >0.3
  • step (3) Weigh 0.137g of the material obtained in step (2), slowly drop into 12.8g of SiO 2 sol, and stir magnetically for 30min.
  • step (3) Drop ammonia water and ethanol diluent into the material obtained in step (3), stir evenly, and let stand to gel.
  • the bulk Y-SiO 2 airgel obtained in this example has a density of 0.29 g/cm 3 , a specific surface area of 861.17 m 2 /g, and an average pore diameter of 10.29 nm.
  • the content of halide ions in the airgel is 0.11wt%.
  • step (3) Weigh 0.228g of the material obtained in step (2), slowly drop into 12.2g of SiO 2 sol, and stir magnetically for 30min.
  • step (3) Drop ammonia water and ethanol diluent into the material obtained in step (3), stir evenly, and let stand to gel.
  • the bulk Y-SiO 2 airgel obtained in this example has a density of 0.10 g/cm 3 , a specific surface area of 844.28 m 2 /g, and an average pore diameter of 13.22 nm.
  • the content of halide ions in the airgel is 0.13wt%.
  • step (3) Weigh 0.684g of the material obtained in step (2), slowly drop into 11.8g of SiO 2 sol, and stir magnetically for 30min.
  • step (3) Drop ammonia water and ethanol diluent into the material obtained in step (3), stir evenly, and let stand to gel.
  • Y-SiO 2 gel was sealed and aged for 22 hours, and then supercritically dried, using ethanol as the supercritical drying medium, and pre-filled with N 2 until the pressure inside the kettle was 2 MPa. Raise the temperature inside the kettle to 270°C at a heating rate of 1°C/min, keep the temperature for 4 hours until the pressure inside the kettle is 10MPa. Turn on the water-cooling device, slowly release the pressure in the kettle to normal pressure, then pass in N 2 to purge the inside of the kettle, and cool to room temperature to obtain Y-SiO 2 airgel.
  • the content of halide ions in the airgel is 0.15wt%.
  • This embodiment provides a kind of silica airgel containing rare earth, silicon micropowder and opacifying agent, and its preparation method comprises the following steps:
  • step (3) Weigh 0.228g of the material obtained in step (2), slowly drop into 12.2g of SiO 2 sol, and stir magnetically for 30min.
  • step (3) Drop ammonia water and ethanol diluent into the material obtained in step (3), stir evenly, and let stand to gel.
  • Y-SiO 2 gel was airtightly aged for 24 hours and then subjected to supercritical drying, using ethanol as the supercritical drying medium, and pre-filled N 2 until the pressure inside the kettle was 2 MPa. Raise the temperature inside the kettle to 270°C at a heating rate of 1°C/min, keep the temperature for 2 hours until the pressure inside the kettle is 12MPa. Turn on the water-cooling device, the rate of pressure drop is 3-4MPa/h, slowly release the pressure in the kettle to normal pressure, pass N 2 into the kettle, and cool to room temperature to obtain Y-SiO 2 airgel.
  • the parameters of the silicon micropowder rare earth doped silica aerogel obtained in this example are compared with conventional silica aerogels as follows. Thermal performance is significantly better than conventional silica aerogels.
  • the Rare earth-doped silica airgel with silicon micropowder conventional silica airgel temperature(°C) Thermal conductivity (W/m ⁇ K) Thermal conductivity (W/m ⁇ K) 300 0.039 0.038 400 0.044 0.0490 500 0.052 0.061 600 0.059 >0.1 700 0.062 >0.1 800 0.068 >0.1 900 0.075 >0.1 1000 0.081 >0.2
  • This embodiment provides a silica airgel containing rare earth, silicon micropowder, opacifying agent and fiber, and its preparation method comprises the following steps:
  • step (3) Weigh 0.228g of the material obtained in step (2), slowly drop into 12.2g of SiO 2 sol, and stir magnetically for 30min.
  • Fiber preforms are glass fiber preforms.
  • Y-SiO 2 gel was airtightly aged for 24 hours and then subjected to supercritical drying, using ethanol as the supercritical drying medium, and pre-filled N 2 until the pressure inside the kettle was 2 MPa. Raise the temperature inside the kettle to 270°C at a heating rate of 1°C/min, and keep the temperature for 2 hours until the pressure inside the kettle is 12MPa. Turn on the water-cooling device, the rate of pressure drop is 3-4MPa/h, slowly release the pressure in the kettle to normal pressure, pass N 2 into the kettle, and cool to room temperature to obtain Y-SiO 2 airgel.
  • This embodiment provides a silica airgel particle containing rare earth, silicon micropowder, opacifying agent, and fiber, and its preparation method includes the following steps:
  • Silica sol preparation Silica sol is prepared by mixing silicon source, water, and alcohol solvent.
  • a hydrolysis catalyst can also be added to the silica sol to accelerate the hydrolysis of the silicon source and obtain silica sol faster.
  • the silicon source can be sodium silicate, ethyl orthosilicate, methyl orthosilicate, tetrapropoxysilane, tetrabutoxysilane, dimethyldimethoxysilane or dimethyldiethoxysilane or its combination.
  • the hydrolysis catalyst can be selected from hydrochloric acid, oxalic acid, nitric acid, sulfuric acid, phosphoric acid or a combination thereof.
  • the alcohol solvent can be methanol, ethanol or a combination thereof.
  • rare earth silica-alumina sol preparing a rare earth compound into a rare earth solution, and mixing the rare earth solution with silica sol and alumina sol to obtain a rare earth silica-alumina sol.
  • the molar ratio of silicon to aluminum is 1:0.1-0.5.
  • the rare earth compound can be yttrium metal salt, scandium metal salt, neodymium metal salt, ytterbium metal salt; yttrium metal oxide, scandium metal oxide, neodymium metal oxide, ytterbium metal oxide.
  • yttrium metal salt can be yttrium nitrate, yttrium chloride, yttrium oxalate, yttrium carbonate; scandium metal salt can be scandium nitrate, scandium chloride, scandium oxalate, scandium carbonate; neodymium metal salt can be neodymium nitrate, neodymium chloride , yttrium oxalate, neodymium carbonate; ytterbium metal salt can be ytterbium nitrate, ytterbium chloride, ytterbium oxalate, ytterbium carbonate.
  • the rare earth solution may contain one or more than one of the above rare earth compounds.
  • Gel preparation A gel catalyst is added to the rare earth silica sol to transform the rare earth silica alumina sol into a rare earth doped gel.
  • the gel catalyst is ammonia water, dimethylformamide, ammonia water ethanol dilution and the like.
  • the drying method may be normal temperature and normal pressure drying, critical drying, supercritical drying and the like.
  • the drying medium of critical drying and supercritical drying can be CO 2 , methanol or ethanol.
  • the conditions for drying at normal temperature and pressure are to dry at 60, 80 and 120° C. for 2 hours respectively, and finally obtain white SiO 2 airgel powder.
  • the condition of carbon dioxide supercritical drying is that in the case of ethanol as the solvent, soak with liquid carbon dioxide at 5°C and 5.5MPa for 3 days, and release the replaced ethanol; then raise the temperature to 35°C and 10.5MPa and keep it for 3h, then Slowly release the pressure to normal pressure at a rate of 0.5 MPa/h to obtain an airgel block.
  • the condition of ethanol supercritical drying is that after raising the temperature and pressure to the critical point according to the preset program, the fluid inside the reactor is released at a slow speed at a constant temperature until the internal and external pressures are balanced.
  • N2 can be used to pre-fill the reactor.
  • the pressure of N2 pre-filling is 1-4Mpa. When the temperature rises above 240°C, the heating rate is 0.5-2°C/min. When the pressure exceeds 8Mpa, turn on the cooling device and release the pressure slowly.
  • N 2 was introduced to purge the reactor, and after cooling to room temperature, a rare earth-doped aerogel was obtained.
  • the thermal conductivity range of the rare earth-doped silicon-aluminum composite airgel is 0.01W/m ⁇ K-0.28W/m ⁇ K at 800°C, and the initial melting temperature of the rare earth-doped silicon-aluminum composite airgel is 1100°C.
  • the thermal conductivity of the heat insulating layer is 0.01W/m ⁇ K-0.045W/m ⁇ K.
  • aluminum-containing substances with stronger fire resistance and high temperature resistance are introduced into the airgel, which solves the problem that the internal silica microstructure of the silica airgel will collapse under high temperature conditions.
  • the present invention also provides a smoke prevention and exhaust air duct
  • the smoke prevention and exhaust air duct includes a metal pipe
  • the inner wall and/or outer wall of the metal pipe is provided with a heat shielding layer
  • the heat shielding layer includes a heat insulating layer
  • the heat insulating layer Including the above-mentioned thermal insulation material or the above-mentioned thermal insulation composite material, or, the thermal insulation layer includes a skeleton, a filler, an anti-shrinkage additive and a high-temperature-resistant additive.
  • the heat shielding layer further includes at least one of a heat conducting layer and a heat reflecting layer.
  • the filler includes silica aerogel, aluminum silicate aerogel, alumina aerogel, composite silica aerogel, rare earth doped silica aerogel at least one of .
  • the filler has a core-shell structure, wherein the shell is aluminum silicate and/or alumina aerogel, the core is silica aerogel, or the shell is silica aerogel and the core is aluminum silicate and/or alumina aerogels.
  • the airgel may be a silica/alumina composite aerogel in which silica and alumina are composited.
  • the skeleton is made of fiber material, which may be at least one of aluminum silicate fiber, alumina fiber, glass fiber, mullite fiber, and SiO 2 ceramic nanofiber.
  • the high temperature resistant additive may be aluminum silicate, quartz powder, silicon micropowder and the like.
  • each air duct unit has a quick connection function, specifically, the anti-smoke air duct is quickly spliced by a front air duct unit and a rear air duct unit.
  • the main structure of each air duct unit includes a metal main frame, an inner wall heat shielding layer attached to the inner wall of the frame, an outer wall heat shielding layer attached to the outer wall of the frame, and a fire-resistant sealant attached to the outside of the outer wall heat shielding layer.
  • the heat shielding layer of the inner wall, the metal main body frame, the heat shielding layer of the outer wall, and the outer refractory sealant are sequentially covered and connected, and the connection method can be physical or chemical connection methods such as rivet fixing and adhesion.
  • the heat-shielding layer of the inner wall and the heat-shielding layer of the outer wall can be composed of a single layer or multiple layers of a heat-insulating layer, a heat-conducting layer, and a heat-reflecting layer.
  • each end of each air duct unit is provided with an extension layer and a receiving area.
  • the smoke prevention air duct includes a front air duct, a rear air duct, a mounting seat, a positioning rod and a positioning cylinder; one end of the front air duct is detachably connected to the rear air duct; the mounting base is symmetrically arranged On the sides of the front air duct and the rear air duct, the positioning rod and the positioning cylinder are correspondingly arranged on the opposite sides of the mounting seats on both sides, and the positioning rod and the positioning cylinder are slidingly fitted;
  • the inner wall and/or outer wall of the front air duct is provided with a heat shielding layer, and the inner wall and/or outer wall of the rear air duct is provided with a heat shielding layer; the heat shielding layer includes at least one of a heat insulating layer, a heat conducting layer, and a heat reflecting layer ;
  • the heat insulation layer is attached to the inner wall and/or outer wall of the front air duct and the rear air duct.
  • the smoke prevention air duct includes a front air duct and a rear air duct; one end of the front air duct is detachably connected to the rear air duct; both ends of the front air duct and the rear air duct are respectively provided with angle steel Flange; the inner wall and/or outer wall of the front air duct is provided with a heat shielding layer, and the inner wall and/or outer wall of the rear air duct is provided with a heat shielding layer; the heat shielding layer includes a heat insulating layer, a heat conducting layer and a heat reflecting layer At least one of them; the heat insulation layer is attached to the inner wall and/or outer wall of the front air duct and the rear air duct.
  • the above connection assembly includes: a surrounding fixing hoop 120 made of metal or other high temperature resistant materials, bolts 121 and nuts 122, as shown in FIG. 7 .
  • the encircling fixing collar 120 also includes a limit hole, and the width of the encircling fixing collar 120 is not less than the length of the outer wall heat shielding layer 200 extending from the air duct.
  • the fixing method after the two air duct units are connected can be as follows: the surrounding fixing hoop 120 covers the gap between the metal pipe 100 of the two air duct units and the heat shielding layer 200, the bolts 121 pass through the corresponding limiting holes, and the nuts 122 Tighten securely.
  • the above technical solution provides a smoke prevention and exhaust air duct structure that can be quickly connected and fixed and has a heat insulation function.
  • the fast connection between the smoke prevention and exhaust air ducts is realized, the work efficiency is improved, and the smoke prevention and exhaust airtightness of the air ducts and the fire resistance performance will not be reduced at the same time, and the practicability is strong.
  • the technical scheme can realize quick connection between two air ducts, improves work efficiency, and at the same time ensures that the air duct's anti-smoke airtightness and fire resistance performance will not be reduced, and has strong practicability.
  • the present invention provides a technical solution, the inventors made the silica airgel part in the composite silica/aluminosilicate airgel particles or silica/alumina airgel particles Further modification and optimization, although silica airgel and aluminum-containing airgel are composited, the silica airgel itself may shrink and collapse under high temperature conditions. Adding anti-shrinkage additives (such as silicon micropowder) to silica airgel can inhibit and reduce the shrinkage and collapse of silica airgel through the crystal form change and volume change of silica micropowder at high temperature, and further improve the composite silica. /The temperature resistance of aluminum silicate airgel particles or composite silica/alumina airgel particles can further improve the temperature resistance of composite airgel, enhance the performance of heat insulation layer and improve the high temperature of anti-smoke and fire-resistant ventilation pipes Performance.
  • anti-shrinkage additives such as silicon micropowder
  • the thermal insulation layer of the gel can withstand high temperature while achieving a low heat transfer coefficient, so that the airgel material can be used in the field of smoke and exhaust ducts, and enhance the heat resistance of the smoke and exhaust ducts. Time to make the smoke exhaust duct work normally.
  • the application of airgel heat insulation material in the smoke prevention and exhaust duct can also reduce the space occupied by the heat insulation material.
  • This technical solution can also solve the problem that the heat insulation material used in the smoke prevention and exhaust duct in the prior art will absorb water, cause the heat insulation structure to collapse, have a short life, and at the same time occupy a large space due to the high thermal conductivity.
  • the structure of the air duct will change and collapse, and the air duct will have defects, resulting in changes in the wind pressure inside the duct, air leakage, and a decrease in the exhaust performance of the air duct.
  • the volume of airgel will shrink in volume at high temperature (above 800 degrees Celsius), which will lead to structural changes and reduce thermal insulation performance.
  • the technical problem to be solved in the embodiment of the present invention is that the thermal insulation layer material will shrink and collapse the internal silica microstructure at high temperature. Problems with materials shrinking and collapsing at high temperatures.
  • the inventors improved and optimized the fillers in the thermal insulation layer, synthesized and used silica/alumina composite aerogels composed of silica and alumina, rare earth-doped silica aerogels
  • the silicon dioxide part in the above-mentioned airgel provides excellent heat insulation ability
  • the alumina part provides excellent temperature resistance performance
  • the rare earth improves the temperature resistance ability.
  • the combination of alumina and silica molecules can inhibit and reduce the shrinkage, melting and crystal form change of silica molecules at high temperature on the microscopic level, and reduce the powder shedding of the thermal insulation layer (airgel felt) on the macroscopic level, making
  • the filler still has thermal insulation performance under high temperature conditions, and maintains relatively good physical and chemical properties to meet the use requirements.
  • the inventor improved the internal structure of the silica airgel material by modifying and optimizing the silica airgel, and made the aluminum oxide/aluminum oxide with better fire resistance but slightly worse heat insulation performance Salt materials are combined with silica airgel to form composite silica airgel particles with an outer shell of aluminum oxide/aluminum salt and a core of silica airgel, or to form a shell of silica airgel with a
  • the inner core is a composite silica airgel particle of aluminum oxide/aluminum salt.
  • the silica airgel can be kept stable at high temperature, and at the same time, the composite particles have good heat insulation performance, and can also maintain good physical and chemical properties. Applying it to the heat insulation layer can meet the requirements of smoke prevention and ventilation. Pipeline usage requirements.
  • the inventors doped the silica airgel with rare earths.
  • the rare earth doping can increase the use temperature of the silica airgel, the application of the airgel under high temperature and extreme conditions can be expanded. It can control the density and microstructure of the aerogel, and further control the anion content in it, thereby controlling the thermal conductivity of the aerogel and its performance at high temperatures.
  • Rare earth elements that can be doped include yttrium, scandium, neodymium and ytterbium.
  • This technical solution can also solve the problem that the heat insulation material used in the smoke prevention and exhaust duct in the prior art will absorb water, cause the heat insulation structure to collapse, have a short life, and at the same time occupy a large space due to the high thermal conductivity.
  • the structure of the air duct will change and collapse, and the air duct will have defects, resulting in changes in the wind pressure inside the duct, air leakage, and a decrease in the exhaust performance of the air duct.
  • the present invention also provides a smoke-exhaust and fire-resistant ventilation duct.
  • the smoke-exhaust and fire-resistant ventilation duct includes a metal pipe, the inner wall and/or outer wall of the metal pipe is provided with a heat shielding layer, and the heat shielding layer includes a high-temperature expansion layer and a heat-insulating layer. It includes at least one of a heat conduction layer and a heat reflection layer, and the heat insulation layer adopts the above-mentioned thermal insulation material or thermal insulation composite material.
  • the high-temperature expansion layer includes a high-temperature foaming agent, multifunctional carbon particles, and a stabilizer.
  • the foaming temperature of the high-temperature foaming agent is greater than 500°C, and the high-temperature foaming agent is silicon carbide powder or granules.
  • the multifunctional carbon particles can be graphite, graphene.
  • the stabilizer is manganese dioxide.
  • the thickness of the high-temperature expansion layer is 1-5mm, and the thickness after expansion is 20-100mm.
  • a preferred solution is to further include airgel particles to improve the thermal insulation performance of the high-temperature expansion layer. The mass proportion of airgel particles added is 3-5%.
  • the high-temperature expansion layer may also contain a water reducer, which is sodium tripolyphosphate or sodium hexametaphosphate.
  • the high-temperature expansion layer expands and foams, and the multifunctional carbon particles in it are not tightly connected due to being dispersed. Thermal conductivity disappears, the high-temperature expansion layer changes from a heat-conducting function to a functional layer with high-temperature heat-insulating properties. At the same time, under this condition, these multifunctional carbon particles can absorb infrared rays and act as a sunscreen, further improving the heat insulation performance under high temperature conditions.
  • a smoke prevention and exhaust air duct with a fast connection and fixing structure, and the air duct is formed by splicing air duct units.
  • each air duct unit is shown in Figure 7 and Figure 8, including the metal main frame, the inner wall heat shielding layer attached to the inner wall of the frame, the outer wall heat shielding layer attached to the outer wall of the frame, and the outer wall heat shielding layer. Fire-resistant sealant attached to the outside of the layer.
  • the heat shielding layer of the inner wall, the metal main body frame, the heat shielding layer of the outer wall, and the outer refractory sealant are sequentially covered and connected, and the connection method can be common physical or chemical connection methods such as rivet fixing and adhesion.
  • the heat shielding layer of the inner wall and the heat shielding layer of the outer wall can be composed of a single layer or multiple layers of heat insulating layer, heat conducting layer and reflective layer.
  • each end of each air duct unit is provided with an extension layer and a receiving area.
  • the metal main frame is a color steel plate.
  • the surface of the metal body frame is coated with an antibacterial coating.
  • the extension layer refers to the structural layer extending outward from the main structure along the direction parallel to the pipe wall at one end of an air duct unit.
  • the receiving area refers to the other end of the extension layer on the air duct unit, which is reserved for connecting with the extension layer of another air duct unit.
  • the structure of the air duct unit can be extended in a single layer or multi-layer according to the structure of the extension layer, so that it can be attached to the extension layer when the air duct unit is connected.
  • the part of the structure that is extended at the receiving end is defined as the extended receiving layer.
  • the two air duct units there are two air duct units to be connected, and the two air ducts have the same structure, both of which include the main body of the air duct unit, the extension layer and the receiving area, excluding the extension receiving layer.
  • the main body of the air duct unit is composed of a metal pipe, a heat shielding layer on the inner wall of the metal pipe, and a heat shielding layer on the outer wall of the metal pipe.
  • the extension length in the direction is the same as the reserved width of the receiving area along the direction parallel to the pipe wall.
  • connection method is: one end of an air duct unit with an extension layer is connected to the end of another air duct unit with a receiving area, and the metal pipes of the two air duct units are in contact, and the extended outer wall heat shield is in contact.
  • One air duct unit has an outer wall heat shield extending from one end of the extension layer, and covers the metal pipe at the other end of the air duct unit having a receiving area. After connecting, the two air duct units fit tightly and are fixed by the connecting components.
  • the above-mentioned connection assembly includes: a surrounding fixing hoop made of metal or other high-temperature-resistant materials, bolts, and nuts.
  • the wrap-around fixing hoop also includes limit holes, and the width of the wrap-around fixing hoop is not less than the length of the heat shielding layer of the outer wall extending from the air duct.
  • the fixing method after the two air duct units are connected can be as follows: the surrounding fixing hoop covers the gap between the metal pipes of the two air duct units and the heat shielding layer, the bolts pass through the corresponding limiting holes, and are tightened with nuts.
  • the air duct can be rectangular, the length of the long side of the air duct is b ⁇ 500mm, the distance between the supports and hangers is d ⁇ 2800mm; Side length b ⁇ 2000mm, support and hanger spacing d ⁇ 1400.
  • the size of the rectangular duct can be 120mm, 160mm, 200mm, 250mm, 320mm, 400mm, 500mm, 630mm, 800mm, 1000mm, 1250mm, 1600mm, 2000mm, 2500mm, 3000mm, 3500mm, 4000mm.
  • the two air duct units to be connected are respectively provided with angle steel flange structures for connection at both ends, and the flanges are made of metal or other high temperature resistant materials.
  • the two angle steel flange structures on both sides of the connection joint of the pipe unit can be closely fitted and fixed by the connection component.
  • connection assembly includes: a plurality of bolts and nuts made of metal or other high temperature resistant materials.
  • the connection method is that the nut passes through the limit hole on the corresponding angle steel flange, and is fixed and locked by bolts.
  • a smoke prevention air duct in a technical solution involved in the present invention, includes a metal pipe 100, the inner wall and/or outer wall of the metal pipe 100 is provided with a heat shielding layer 200, and the heat shielding layer 200 includes At least one of the heat insulating layer 210 , the heat conducting layer 220 , and the heat reflecting layer 230 .
  • the thermal insulation layer can use the thermal insulation material mentioned above or the thermal thermal insulation composite material mentioned above.
  • the heat conduction layer 220 can be a metal heat conduction plate, such as copper, aluminum and other metal materials with high heat conduction performance; it can also be a heat conduction metal structure, such as a hollow heat conduction interlayer; it can also be the heat conduction layer 220 of a device provided with a heat pipe.
  • a metal heat conduction plate such as copper, aluminum and other metal materials with high heat conduction performance
  • it can also be a heat conduction metal structure, such as a hollow heat conduction interlayer
  • it can also be the heat conduction layer 220 of a device provided with a heat pipe.
  • the heat conducting layer 220 , the heat reflecting layer 230 , and the heat insulating layer 210 are sequentially stacked to form the heat shielding layer 200 .
  • Another arrangement is that the heat reflection layer 230 , the heat conduction layer 220 , and the heat insulation layer 210 are stacked in sequence to form the heat shielding layer 200 .
  • the heat insulating layer 210 is attached to the inner wall and/or the outer wall of the metal pipe 100 .
  • a smoke prevention air duct includes a front air duct 140 and a rear air duct 150, and one end of the front air duct 140 is detachably connected to the rear air duct 150.
  • the smoke prevention and exhaust air duct also includes a mounting base 160, a positioning rod 161 and a positioning cylinder 162.
  • the mounting base 160 is symmetrically arranged on the sides of the front air duct 140 and the rear air duct 150, and the positioning rod 161 and the positioning cylinder 162 correspond to They are arranged on opposite sides of the mounting bases 160 on both sides, and the positioning rod 161 and the positioning cylinder 162 are slidably matched, as shown in FIG. 8 .
  • first connection assembly and a second connection assembly are provided between the front air pipe and the rear air pipe;
  • the first connection assembly includes a limit hole, a guide hole, a limit rod and a nut, and the limit hole runs through the vertical
  • a smoke prevention air duct in one technical solution involved in the present invention, includes a metal pipe, the inner wall and/or outer wall of the metal pipe is provided with a heat shielding layer, and the heat shielding layer includes a heat insulating layer, a heat conducting At least one of layer, heat reflective layer.
  • the thermal insulation layer can use the thermal insulation material mentioned above or the thermal thermal insulation composite material mentioned above.
  • the heat conduction layer can be a metal heat conduction plate, such as copper, aluminum and other metal materials with high heat conduction performance; it can also be a heat conduction metal structure, such as a hollow heat conduction interlayer; it can also be a heat conduction layer of a device provided with a heat pipe.
  • a metal heat conduction plate such as copper, aluminum and other metal materials with high heat conduction performance
  • it can also be a heat conduction metal structure, such as a hollow heat conduction interlayer
  • it can also be a heat conduction layer of a device provided with a heat pipe.
  • the heat conducting layer, the heat reflecting layer and the heat insulating layer are stacked in sequence to form the heat shielding layer.
  • Another arrangement is that the heat reflection layer, the heat conduction layer, and the heat insulation layer are stacked in sequence to form a heat shielding layer.
  • the thermal insulation layer is attached to the inner wall and/or outer wall of the metal pipe.
  • the form of the heat conduction layer includes silica gel heat dissipation film, graphite heat dissipation film, metal heat conduction plate, heat pipe heat conduction plate.
  • the material of the metal heat conducting plate can be a copper plate or an aluminum plate.
  • the form of the heat conduction layer can also be a channel with a heat conduction structure, such as a double-layer hollow metal heat conduction plate.
  • the range of thermal conductivity of the heat conducting layer at 800°C is 20W/m ⁇ K-50W/m ⁇ K.
  • a heat conduction layer on the smoke exhaust duct can enhance the heat conduction and heat dissipation performance of the smoke exhaust duct, prevent local high temperature, and prevent the internal silica airgel particles from melting at high temperatures such as 600 ° C, so that the heat insulation layer can be used at high temperatures It can still maintain the structure stability under the circumstances, and meet the use requirements of the smoke prevention and exhaust duct.
  • the inventor also believes that the local high temperature can be reduced by setting a heat absorbing layer inside the smoke prevention and exhaust duct, so that the smoke prevention and exhaust duct can withstand higher temperatures.
  • a smoke prevention air duct in one technical solution involved in the present invention, includes a metal pipe, the inner wall and/or outer wall of the metal pipe is provided with a heat shielding layer, the heat shielding layer includes a heat insulating layer, and the heat insulating
  • the layer can use the above heat insulation material or the above heat insulation composite material, and the heat shielding layer can also include at least one of a heat conducting layer, a heat reflecting layer, and a heat absorbing layer.
  • a preferred method is that the heat conducting layer, the heat reflecting layer, the heat absorbing layer and the heat insulating layer are stacked in sequence to form the heat shielding layer.
  • the heat conducting layer, the heat reflecting layer, the heat absorbing layer and the heat insulating layer are stacked in sequence to form a heat shielding layer.
  • Another arrangement is that the heat reflective layer, the heat absorbing layer, and the heat insulating layer are stacked in sequence to form a heat shielding layer.
  • the thermal insulation layer is attached to the inner wall and/or outer wall of the metal pipe.
  • the heat absorbing layer is composed of heat storage materials.
  • the heat storage materials can be phase change materials, heated volatile materials, etc., and can also be preset cooling materials such as preset water tanks, preset carbon dioxide tanks, etc., which can be released when encountering high temperatures.
  • the loaded water, carbon dioxide and other cooling carriers absorb heat.
  • the phase change material can absorb heat and keep the temperature constant, so that in the case of local high temperature, the absorbed heat produces a phase change without increasing the temperature, thereby protecting the airgel structure of the heat insulation layer from collapsing, so that the heat insulation layer maintains the heat insulation effect , so that the entire heat shielding layer can still maintain the temperature insulation effect at high temperatures.
  • Phase change materials are molten salts, and molten salts include carbonates, chloride salts, and fluoride salts.
  • Installing a heat absorbing layer in the smoke exhaust duct can reduce the temperature of the smoke exhaust duct, prevent local high temperature, and prevent the internal silica airgel particles from melting at high temperatures such as above 600°C, so that the airgel heat insulation can reach the use Require.
  • the heat insulating layer, the heat conducting layer, the heat reflecting layer and the heat absorbing layer are fixed to each other by bonding and hot pressing.
  • the outside of the heat shielding layer can also be wrapped with glass fiber cloth and aluminum foil to prevent the filler from breaking and falling off.
  • the invention uses tetraethyl orthosilicate and rare earth nitrate as raw materials, ethanol as solvent, acid and alkali as catalyst, adopts sol-gel method to prepare rare earth doped silica wet gel, after solvent replacement and ethanol supercritical drying A massive rare earth doped silica airgel was obtained.
  • the method can increase the use temperature of the silica airgel by doping rare earth elements in the silica airgel, and expand the application of the airgel under high-temperature extreme conditions.
  • the density and microstructure of the airgel can be controlled, thereby controlling the thermal conductivity of the airgel.
  • the method has the advantages of simple process, high production efficiency, and is favorable for large-scale production.

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Abstract

一种稀土掺杂二氧化硅气凝胶及其制备方法和包括所述气凝胶的颗粒，属于气凝胶及其制备。所述稀土掺杂二氧化硅气凝胶为块状稀土掺杂二氧化硅气凝胶，所述气凝胶中的卤素离子含量不高于0.2wt％。通过在二氧化硅气凝胶中掺入稀土元素，提高二氧化硅气凝胶使用温度，降低气凝胶导热系数，所得气凝胶密度低、比表面积高，有良好隔热性能。所述制备方法工艺简单，生产效率高，设备要求较低，利于大规模生产，避免稀土元素在二氧化硅基体中分散不均匀的问题。

Description

一种稀土掺杂二氧化硅气凝胶及其制备方法和应用
本申请要求2021年9月17日向中国国家知识产权局提交的专利申请号为202111091766.1，发明名称为“一种稀土掺杂二氧化硅气凝胶的制备方法”的在先申请的优先权。这篇在先申请的全文通过引用的方式结合于本申请中。
本申请要求2022年4月22日向中国国家知识产权局提交的PCT申请号为PCT/CN2022/088412，发明名称为“一种耐高温防排烟风管及其制造方法”的在先申请的优先权。这篇在先申请的全文通过引用的方式结合于本申请中。
本申请要求2022年4月22日向中国国家知识产权局提交的PCT申请号为PCT/CN2022/088413，发明名称为“一种耐高温气凝胶防排烟风管及其制造方法”的在先申请的优先权。这篇在先申请的全文通过引用的方式结合于本申请中。
技术领域
本发明属于气凝胶及其制备技术领域，具体是涉及一种稀土掺杂二氧化硅气凝胶及其制备方法。
背景技术
随着超音速飞行器的快速发展，飞行器的头锥、机翼和发动机的喷管等长时间遭受气动加热，传统的保温隔热材料已无法满足当前的使用需求，因此研制综合性能优异的保温隔热材料非常必要。气凝胶是一种具有纳米级孔的新型隔热保温材料，其中二氧化硅SiO 2气凝胶当前应用最为广泛。但由于二氧化硅SiO 2气凝胶在高温下容易烧结发生结构坍塌，其长期使用温度仅为650℃。因此一般通过掺入异质元素来提升其高温稳定性。稀土硅酸盐作为一种环境屏障涂层，具有良好的高温稳定性及优异的隔热性能，但是现有的稀土硅酸盐陶瓷孔隙率偏低(50％～70％)、孔径偏大(0.4～3.5μm)，在高温环境中热导率会急速上升，不适用于高温隔热。
发明内容
研究发现，稀土元素能与其他材料组成性能各异、品类繁多的新型材料，因此稀土掺杂二氧化硅气凝胶可以兼具气凝胶优越的纳米结构以及稀土材料的耐温特性，在保温隔热方面 具有非常大的应用前景。基于此，本发明提供一种稀土掺杂二氧化硅气凝胶，该气凝胶可以兼具气凝胶优越的纳米结构以及稀土材料的耐温特性。具体的，由于稀土的掺杂可提高二氧化硅气凝胶的使用温度，扩展气凝胶在高温极端条件下应用，能控制气凝胶的密度、微观结构，进一步通过控制其中阴离子的含量，从而控制气凝胶的导热系数，该气凝胶在保温隔热方面具有非常大的应用前景。本发明还提供一种制备上述稀土掺杂二氧化硅气凝胶的方法，所述方法的工艺简单易行、生产效率高、有利于大规模生产所述稀土掺杂二氧化硅气凝胶。
发明人在实现本发明人的过程中，发明人发现稀土掺杂二氧化硅气凝胶在使用过程中，会腐蚀其他的材料，比如金属其包裹的金属管线。发明人通过研究发现，造成腐蚀的主要原因是残留的阴离子杂质元素，如氯离子。稀土掺杂气凝胶中的氯离子主要来自于气凝胶制备工艺中的稀土原料。
本发明具体公开以下方案：
一种稀土掺杂二氧化硅气凝胶，所述气凝胶为块状稀土掺杂二氧化硅气凝胶，所述气凝胶中的卤素离子含量不高于0.2wt％。
根据本发明，所述稀土元素选自钇Y、钪Sc、和La系稀土金属中的至少一种，稀土元素记REE(Rare Earth Element)。
根据本发明，所述稀土元素在所述气凝胶中以REE-O-Si键形式存在。
根据本发明，所述气凝胶中，所述稀土元素与Si元素和氧元素一起构成网状非晶体结构。
根据本发明，所述稀土元素均匀分布在所述网状非晶体结构中。
根据本发明，所述气凝胶具备下述性能中的至少一种：
1)密度为0.08～0.35g/cm 3；
2)比表面积为640～880m 2/g；
3)平均孔径为10nm～22nm；
4)疏水角为85°～130°。
根据本发明，所述气凝胶中还包括硅微粉、遮光剂、纤维和铝中的至少一种。
本发明还提供一种上述稀土掺杂二氧化硅气凝胶的制备方法，所述方法包括以下步骤：
1)制备硅溶胶：将硅源、水、醇溶剂混合制备硅溶胶；
2)制备稀土硅溶胶：配置稀土化合物溶液，并将稀土化合物溶液与上述硅溶胶混合，得到稀土硅溶胶；所述稀土化合物为稀土金属硝酸盐、稀土金属草酸盐、稀土金属碳酸盐或稀土金属氧化物中的至少一种；
3)制备凝胶：向上述稀土硅溶胶中加入凝胶催化剂，稀土硅溶胶转变为稀土掺杂凝胶，记为稀土-SiO 2凝胶；
4)溶剂置换步骤：使用乙醇置换出稀土-SiO 2凝胶中的水、卤素离子及其他杂质；
5)干燥：对上述稀土-SiO 2凝胶进行乙醇超临界干燥，得到稀土掺杂二氧化硅气凝胶。
根据本发明，步骤1)的硅溶胶中，还可以加入硅微粉。
根据本发明，步骤1)的硅溶胶中，还可以加入遮光剂。
根据本发明，所述方法中采用多种硅源与多种稀土化合物的组合。
根据本发明，步骤3)制备凝胶过程中还引入纤维，采用下述两种方式中的一种：
第一种方式：向上述稀土硅溶胶中加入凝胶催化剂后，将其浇筑至纤维预制件中，之后静置获得凝胶；
第二种方式：向上述稀土硅溶胶中加入凝胶催化剂后，再加入增强纤维以及纤维分散剂，之后静置获得凝胶。
根据本发明，步骤4)之前还包括一个改性步骤，具体包括：
3’)改性：将上述稀土-SiO 2凝胶与改性剂混合，得到改性的稀土-SiO 2凝胶；
4)溶剂置换：使用乙醇进行溶剂置换。
本发明还提供一种二氧化硅气凝胶颗粒，所述颗粒具有核壳结构；其中，外壳是铝氧化物和/或铝盐而内核是上述的稀土掺杂二氧化硅气凝胶，或者，外壳是上述的稀土掺杂二氧化硅气凝胶而内核是铝氧化物和/或铝盐。
本发明还提供一种所述二氧化硅气凝胶颗粒的制备方法，所述制备方法包括以下步骤：
先制备所述稀土掺杂二氧化硅气凝胶颗粒，然后与铝氧化物和/或铝盐混合，制备得到所述外壳是铝氧化物和/或铝盐而内核是上述的稀土掺杂二氧化硅气凝胶的颗粒；
或者，采用上述的稀土掺杂二氧化碳气凝胶的制备方法制备所述气凝胶，其中在所述步骤3)的制备凝胶的过程中加入铝氧化物和/或铝盐颗粒，从而可以制备得到所述外壳是上述的稀土掺杂二氧化硅气凝胶而内核是铝氧化物和/或铝盐的颗粒。本发明的有益效果：
1)本发明先采用溶胶凝胶法制备稀土掺杂二氧化硅湿凝胶，通过乙醇的置换，然后经乙醇超临界干燥后得到块状稀土掺杂二氧化硅气凝胶，制得的气凝胶密度低，比表面积高，具有良好的隔热性能；另外，其疏水角在85°～130°，在用于与纤维混合制备复合材料时具有掉粉少，应用GBT 4857.7-2005标准测试，复合材料的质量损失率＜5％。该气凝胶的制备工艺简单易行，生产效率高，对设备要求较低，有利于大规模生产。
2)本发明的气凝胶中的卤素离子(特别时氯离子)含量不高于0.2％；具体的，本发明的气凝胶中卤素离子(特别时氯离子)含量不高于0.15％，甚至可以不含有卤素离子(特别是氯离子)。
3)本发明的气凝胶密度低，比表面积高，具有良好的隔热性能；另外，其疏水角在85°～130°，在用于与纤维混合制备复合材料时具有掉粉少的特性，应用GBT 4857.7-2005标准测试，复合材料的质量损失率＜5％。
4)本发明的气凝胶具备在高温下使用的性能，在800-1200℃仍能保持隔热效果，可扩展应用到高温极端条件。
5)本发明通过控制乙醇含量、稀土掺杂量及成型工艺，选择特定的含稀土化合物等，能控制气凝胶的密度、微观结构，控制气凝胶中卤素离子(特别是氯离子)含量，从而降低了气凝胶在使用过程中对其他物体的腐蚀情况。同时在溶胶凝胶过程中，引入液相异质元素(稀土元素)，降低了气凝胶在高温情况下导热系数，提高了其高温情况的保温隔热性能。
附图说明
图1为本发明实施例1制备的块状Y-SiO 2气凝胶的宏观图。
图2为本发明实施例1制备的块状Y-SiO 2气凝胶的N 2吸附-脱附曲线和孔径分布图。
图3为本发明实施例1制备的块状Y-SiO 2气凝胶的SEM微观形貌图。
图4为本发明的块状Y-SiO 2气凝胶制备流程示意图。
图5为本发明实施例6制备的块状Y-SiO 2气凝胶的高温导热系数图。
图6为纤维增强的Y-SiO 2气凝胶复合材料制备流程示意图。
图7为本发明的防排烟风管示意图。
图8为本发明的快速拆装风管示意图。
图9为本发明的热屏蔽层示意图。
图10为本发明的绝热层包裹耐高温保护层示意图。
图11为本发明的高温膨胀层在不同温度下形态示意图。
图12为本发明的排烟风管结构示意图。
图13枝晶陶瓷纤维气凝胶示意图。
图中：100-金属管道；101-抗菌金属管道；110-角钢法兰；120-环绕式固定箍；121-螺栓；122-螺母；130-耐火密封胶；200-热屏蔽层；210-绝热层；220-导热层；230-热反射层；250-耐高温保护层；260-高温膨胀层；300-陶瓷纤维；310-陶瓷枝晶；320-枝晶陶瓷纤维气凝胶。
具体实施方式
[稀土掺杂二氧化硅气凝胶]
如前所述，本发明提供一种稀土掺杂二氧化硅气凝胶，为块状稀土掺杂二氧化硅气凝胶，所述气凝胶中的卤素离子含量不高于0.2wt％。
研究发现，卤素离子、特别是氯离子的存在会带来腐蚀性，不利于气凝胶的使用。本发明提供一种卤素离子含量极低的气凝胶，减少了其对被保温物体的腐蚀，提高了气凝胶作为隔热、保温材料的应用前景。
另外，本发明在二氧化硅气凝胶中掺杂稀土元素，掺杂的稀土元素可以抑制所述二氧化硅气凝胶材料的高温烧结情况，改善材料耐高温性能，而且对气凝胶材料的空间网络结构有良好的支撑效果，可以有效阻止孔结构的坍塌，提高其在高温下的隔热性能。
根据本发明的一个实施方式，所述稀土选自钇Y、钪Sc、和La系稀土金属(如选自钕Nd、镱Yb等)等中的至少一种。
根据本发明的一个实施方式，所述稀土在所述气凝胶中以REE-O-Si键形式存在。
根据本发明的一个实施方式，所述气凝胶中卤素离子(特别是氯离子)的含量不高于0.15wt％；具体的可以不含有卤素离子(特别是氯离子)。
根据本发明的一个实施方式，本发明的气凝胶密度低，比表面积高，卤素离子含量低甚至不含有卤素离子(如氯离子)，具有良好的隔热性能。
根据本发明的一个实施方案，所述气凝胶中，所述稀土元素与Si元素和氧元素一起构成网状非晶体结构。具体地，所述稀土元素均匀分布在所述网状非晶体结构中。
根据本发明的一个实施方案，所述气凝胶的密度为0.08～0.35g/cm 3；例如为0.10～0.30g/cm 3；具体地为0.08g/cm 3、0.10g/cm 3、0.12g/cm 3、0.14g/cm 3、0.17g/cm 3、0.20g/cm 3、0.22g/cm 3、0.24g/cm 3、0.27g/cm 3、0.29g/cm 3、0.30g/cm 3或0.35g/cm 3。
根据本发明的一个实施方案，所述气凝胶的比表面积为640～880m 2/g；具体地为640m 2/g、648.17m 2/g、844.28m 2/g、861.17m 2/g或880m 2/g。
根据本发明的一个实施方案，所述气凝胶的平均孔径为10nm～22nm；具体地为10nm、10.29nm、11nm、12nm、13nm、13.22nm、14nm、15nm、16nm、17nm、18nm、19nm、20nm、20.45nm、21nm或22nm。
根据本发明的一个实施方案，所述气凝胶中还包括硅微粉、遮光剂、纤维和铝中的至少一种。
具体地，所述遮光剂可以是二氧化钛、炭黑、SiC、六钛酸钾、ZrO 2中的至少一种。
具体地，所述纤维选自水镁石纤维、陶瓷纤维、玻璃纤维、石英纤维中的至少一种。
具体地，所述纤维为增强纤维，例如，所述增强纤维可以是硅酸铝纤维、氧化铝纤维、玻璃纤维、莫来石纤维、SiO 2陶瓷纳米纤维的至少一种。
根据本发明的一个实施方案，所述气凝胶的疏水角为85°～130°。
[稀土掺杂二氧化硅气凝胶的制备方法]
如前所述，本发明提供了一种上述稀土掺杂二氧化硅气凝胶的制备方法，所述方法先采用溶胶凝胶法制备得到湿凝胶，且用乙醇置换，然后通过干燥(特别是超临界干燥)制备得到所述稀土掺杂二氧化硅气凝胶，具体地所述方法包括以下步骤：
1)制备硅溶胶：将硅源、水、醇溶剂混合制备硅溶胶；
2)制备稀土硅溶胶：配置稀土化合物溶液，并将稀土化合物溶液与上述硅溶胶混合，得到稀土硅溶胶；所述稀土化合物为稀土金属硝酸盐、稀土金属草酸盐、稀土金属碳酸盐或稀土金属氧化物中的至少一种；
3)制备凝胶：向上述稀土硅溶胶中加入凝胶催化剂，稀土硅溶胶转变为稀土掺杂凝胶，记为稀土-SiO 2凝胶；
4)溶剂置换步骤：使用乙醇置换出稀土-SiO 2凝胶中的水、卤素离子及其他杂质；
5)干燥：对上述稀土-SiO 2凝胶进行乙醇超临界干燥，得到稀土掺杂二氧化硅气凝胶。
本发明的方法的工艺简单易行、生产效率高、有利于大规模生产所述稀土掺杂二氧化硅气凝胶。进一步的，本发明先采用溶胶凝胶法制备稀土掺杂二氧化硅湿凝胶，且通过乙醇的置换，然后经乙醇超临界干燥后得到块状稀土掺杂二氧化硅气凝胶，制得的气凝胶密度低，比表面积高，具有良好的隔热性能；另外，制备的气凝胶具有疏水性，其疏水角在85°～130°；再有，所述气凝胶在用于与纤维混合制备复合材料时具有掉粉少的特性，具体地，应用GBT4857.7-2005标准测试，复合材料的质量损失率＜5％。
根据本发明的一个实施方式，步骤1)中，还可以向硅溶胶中加入水解催化剂，目的在于加速硅源水解，更快获得硅溶胶。
根据本发明的一个实施方式，所述步骤1)具体包括：将硅源、醇溶剂与水按比例依次加入容器中，混合，加入水解催化剂，再混合，静置，得到硅溶胶。
根据本发明的一个实施方式，步骤1)中，硅源、醇溶剂与水按照摩尔比1:(7～20):3的比例依次加入容器中；具体地，硅源、醇溶剂与水按照摩尔比为1:8～15:3的比例依次加入容器中。
根据本发明的一个实施方式，步骤1)中，所述硅源选自硅酸钠、正硅酸乙酯、正硅酸甲酯、四丙氧基硅烷、四丁氧基硅烷、二甲基二甲氧基硅烷或二甲基二乙氧基硅烷中的至少一种。
根据本发明的一个实施方式，步骤1)中，所述醇溶剂是甲醇、乙醇或其组合。
根据本发明的一个实施方式，步骤1)中，第一次混合的时间为10min～15min。
根据本发明的一个实施方式，步骤1)中，所述水解催化剂选自盐酸、草酸、硝酸、硫酸、磷酸或其组合。
根据本发明的一个实施方式，步骤1)中，所述水解催化剂以滴加方式加入；具体地可通过恒压漏斗滴加。
根据本发明的一个实施方式，步骤1)中，所述水解催化剂以溶液形式加入，水解催化剂溶液的质量分数为0.05～0.1wt％，硅源与水解催化剂的摩尔比可为1:(10～4)。
根据本发明的一个实施方式，步骤1)中，第二次混合的时间为100min～120min。
根据本发明的一个实施方式，在步骤1)中，所述静置的时间可为20h～48h，例如为20h、22h、24h、26h、28h、30h、32h、34h、36h、38h、40h、42h、44h、46h或48h。所述时间的选择使得水解反应充分而缓慢地进行即可。
在本发明所涉及的一个技术方案中，步骤1)的硅溶胶中，还可以加入硅微粉。具体的步骤1)为制备硅溶胶：将硅源、水、醇溶剂、硅微粉混合制备硅溶胶，向硅溶胶中加入水解催化剂加速硅源水解，更快获得硅溶胶。
具体地，所述硅微粉粒径范围是600目-1500目，所述硅微粉是非晶态(无定型)硅微粉，所述硅微粉的添加量是1％-15％。
在本发明所涉及的一个技术方案中，步骤1)的硅溶胶中，还可以加入遮光剂，目的在于增强在高温情况下的隔温性能。
具体地，所述遮光剂包括二氧化钛、炭黑、SiC、六钛酸钾、ZrO 2等中的至少一种。进一步的，二氧化钛可以是锐钛矿型二氧化钛。进一步的，二氧化钛可以是氟掺杂或者氮掺杂的二氧化钛纳米颗粒，引入这样的二氧化钛可以增强红外波段辐射的遮光效果。
根据本发明的一个实施方式，步骤2)中，配置稀土化合物溶液的具体过程包括：将稀土化合物溶于水中，加热反应后，冷却至室温后得到稀土化合物溶液。
根据本发明的一个实施方式，步骤2)中，所述稀土化合物为稀土金属硝酸盐、稀土金属草酸盐、稀土金属碳酸盐或稀土金属氧化物中的至少一种；例如所述稀土选自钇Y、钪Sc、和La系稀土金属(如选自钕Nd、镱Yb等)等中的至少一种。还例如，所述稀土化合物是两种以上的组合，具体地例如是钇金属硝酸盐、草酸盐或碳酸盐中的至少一种和钪金属硝酸盐、草酸盐或碳酸盐中的至少一种的组合。
根据本发明的一个实施方式，步骤2)中，所述稀土化合物为稀土金属硝酸盐、稀土金属草酸盐、稀土金属碳酸盐中的至少一种。具体为稀土金属硝酸盐水合物，例如所述稀土化合物为Y(NO 3) 3·4H 2O、Sc(NO 3) 3·6H 2O、Nd(NO 3) 3·6H 2O、Yb(NO 3) 3·5H 2O等中的至少一种。本发明中采用硝酸盐、草酸盐或碳酸盐作为稀土原料，如硝酸钇、硝酸钪、硝酸钕、草酸钇、草酸钪、草酸钕、碳酸钇、碳酸钪和碳酸钕，避免了卤素离子的引入，进一步实现了气凝胶中卤素离子的含量控制。
在本发明所涉及的一个技术方案中，所述方法中采用多种硅源与多种稀土化合物的组合。
具体地，所述硅源可选用硅酸钠、正硅酸乙酯、正硅酸甲酯、四丙氧基硅烷、四丁氧基硅烷、二甲基二甲氧基硅烷或二甲基二乙氧基硅烷中的两种以上的组合。
具体地，所述稀土化合物可选用钇金属硝酸盐、草酸盐或碳酸盐中的至少一种、钪金属硝酸盐、草酸盐或碳酸盐中的至少一种、La系金属硝酸盐、草酸盐或碳酸盐中的(如钕金属硝酸盐、草酸盐或碳酸盐中的至少一种、镱金属硝酸盐、草酸盐或碳酸盐中的至少一种)、钇金属氧化物、钪金属氧化物、La系金属氧化物(如钕金属氧化物、镱金属氧化物)的两种以上的组合。进一步的，钇金属盐可以是硝酸钇、氯化钇、草酸钇、碳酸钇；钪金属盐可以是硝酸钪、氯化钪、草酸钪、碳酸钪；钕金属盐可以是硝酸钕、氯化钕、草酸钇、碳酸钕；镱金属盐可以是硝酸镱、氯化镱、草酸镱、碳酸镱。
进一步的，稀土化合物溶液中可以包含两种以上上述稀土化合物。
根据本发明的一个实施方式，步骤2)的配置稀土化合物溶液的过程中，采用水浴加热。加热的温度可以为40℃～60℃，例如为45～50℃；加热的时间可以为20min～60min，例如加热的时间可为30min～35min。
根据本发明的一个实施方式，在步骤2)的配置稀土化合物溶液的过程中，所述稀土硝酸盐与水的质量比可为(3～4):1。
根据本发明的一个实施方式，步骤3)中，所述凝胶催化剂选自氨水、二甲基甲酰胺、氨水乙醇稀释液、碳酸氢铵、碳酸铵等中的至少一种。具体地，所述凝胶催化剂采用滴加方式加入。
根据本发明的一个实施方式，步骤3)中，所述凝胶催化剂优选NH 3·H 2O、NH 4HCO 3和(NH 4) 2CO 3，可以避免引入其他杂质，其中NH 3·H 2O的合适用量为n(Si):n(NH 3·H 2O)＝1:0.0.1～0.25。
根据本发明的一个实施方式，步骤3)中，所述物料中硅源与凝胶催化剂的摩尔比可为1:(0.1～0.25)。
在本发明所涉及的一个技术方案中，步骤3)制备凝胶过程中还引入纤维；具体的步骤3)制备凝胶的过程为：向上述稀土硅溶胶中加入凝胶催化剂后，将其浇筑至纤维预制件中，之后静置获得凝胶。
具体的，所述纤维预制件可以由水镁石纤维、陶瓷纤维、玻璃纤维、石英纤维中的至少一种制成。
具体的，所述静置时间可以是24h～72h。
在本发明所涉及的一个技术方案中，步骤3)制备凝胶过程中还引入纤维；具体的步骤3)制备凝胶的过程为：向上述稀土硅溶胶中加入凝胶催化剂后，再加入增强纤维以及纤维分散剂，之后静置获得凝胶。
具体地，所述纤维分散剂可以是十二烷基磺酸钠、聚乙二醇、十二烷基硫酸钠、六偏磷酸钠等。
具体地，所述增强纤维可以是硅酸铝纤维、氧化铝纤维、玻璃纤维、莫来石纤维、SiO 2陶瓷纳米纤维的至少一种。
具体地，所述莫来石纤维可以是枝晶增强莫来石纤维。所述枝晶增强莫来石纤维的制备方法是，将硅酸铝纤维浸入浸渍液，再将其冷冻干燥；重复浸渍、冷冻干燥过程3次后干燥，第1次浸 渍液是硅溶胶，第2次浸渍液是AINO 3，第3次浸渍液是NH 4F溶液，三次浸渍的硅源、铝源、氟源的摩尔比例是1:3:12。
在本发明所涉及的一个技术方案中，步骤4)之前还包括一个改性步骤，具体包括：
3’)改性：将上述稀土-SiO 2凝胶与改性剂混合，得到改性的稀土-SiO 2凝胶；
4)溶剂置换：使用乙醇进行溶剂置换。
具体的，所述步骤3’)包括：将上述稀土-SiO 2凝胶浸泡于改性剂中，得到改性的稀土-SiO 2凝胶。
具体地，步骤3’)中，所述浸泡时间可以为4h～48h。
具体地，步骤3’)中，所述改性剂是有机硅烃类化合物溶液，溶液中有机硅烃类化合物的质量分数是0.5～5％。具体地，所述有机硅烃类化合物可为氯三甲基硅烷、十三氟辛基三乙氧基硅烷、十七氟癸基三乙氧基硅烷、十三氟辛基三甲氧基硅烷、十七氟癸基三甲氧基硅烷、乙酰氧基三甲基硅烷、苄基二甲基氯硅烷、苄基三氯硅烷、苄基三乙氧基硅烷、叔丁基三甲基氯硅烷、二氯异丁基甲基硅烷、正丁基三氯硅烷、环乙基三氯硅烷、3-氯环戊基硅烷或二丁基二氯化硅中的至少一种。具体地，所述有机硅烃类化合物溶液中的溶剂为正己烷、乙醇、四氢呋喃、N，N-二甲基甲酰胺、N，N-二甲基乙酰胺、氯仿、二氯甲烷、甲醇、四氯化碳、嘧啶、二甲苯、环己烷、甲乙酮或乙酸甲酯中的至少一种。
具体的，步骤4)中，所述置换用有机溶剂可以是乙醇、异丙醇、正己烷的一种或其组合。
根据本发明的一个实施方式，步骤5)中，先将上述稀土-SiO 2凝胶密闭静置老化后再进行超临界干燥。
根据本发明的一个实施方式，步骤5)中，所述静置老化的时间可为22～24h。
根据本发明，步骤5)中采用乙醇超临界干燥，不仅可以提高疏水性，还可以降低掉粉的问题，提高气凝胶的品质。
根据本发明的一个实施方式，步骤5)的干燥的条件为：以乙醇为超临界干燥的介质，预充N 2使得釜内到一定压力；以一定升温速率将釜内温度升至设定温度，保温一定时间至釜内压力达到某一设定值；打开水冷装置，释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到稀土掺杂二氧化硅气凝胶。
根据本发明的一个实施方式，步骤5)中，乙醇超临界干燥的条件是，按预设程序升温升压至临界点后，在恒定温度状态下，以缓慢的速度释放反应釜内部的流体，直至内外压力平衡。升温前可以使用N 2预先充满反应釜，预充N 2的压力为1-4MPa，升温至240℃以上，升 温速率0.5-2℃/min，当压力超过8MPa后，开启冷却装置，缓慢泄压，泄压至常压后通入N2吹扫反应釜，待冷却至室温后，得到稀土掺杂气凝胶。具体的，所述超临界干燥的条件可为：以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa，以1℃/min的升温速率将釜内温度升至270℃，保温2～4h至釜内压力为8～10MPa，打开水冷装置，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到稀土掺杂二氧化硅气凝胶。
[二氧化硅气凝胶颗粒]
本发明还提供一种二氧化硅气凝胶颗粒，所述颗粒具有核壳结构；其中，外壳是铝氧化物和/或铝盐而内核是上述的稀土掺杂二氧化硅气凝胶，或者，外壳是上述的稀土掺杂二氧化硅气凝胶而内核是铝氧化物和/或铝盐。
研究发现，当向所述稀土掺杂二氧化硅气凝胶中加入硅微粉时，通过硅微粉在高温下的晶型变化、体积变化，可以抑制和减少所述二氧化硅气凝胶的收缩坍塌问题，进一步提高所述二氧化硅气凝胶颗粒的耐温性能。
在一些实施例中，硅微粉的粒径是1000-3000目。
在一些实施例中，硅微粉的添加量是1％-15％。
在一些实施例中，硅微粉的表面覆有二氧化钛膜。示例性的，所述二氧化钛是氮掺杂或者氟掺杂的二氧化钛。研究发现，因此将二氧化钛镀膜至硅微粉表面，再加入气凝胶中，既可以发挥硅微粉在高温情况下调节抑制二氧化硅气凝胶收缩的特点，还可以解决二氧化钛团聚的问题，从而进一步的提升二氧化硅气凝胶的高温隔热性能。
研究发现，利用硅微粉，特别是非晶态二氧化硅微粉在高温情况下的晶相变化导致的体积变化，调整和抑制气凝胶颗粒在高温下的收缩情况，同时非晶态硅微粉还可以提升气凝胶颗粒的温度耐受能力。非晶态硅微粉是二氧化硅材料，在温度变化下会有晶型的转变带来的体积变化的现象。非晶态硅微粉体积的膨胀在气凝胶颗粒经历高温过程中会抑制和降低内应力，从而减少气凝胶颗粒内部的结构变化而稳定其在高温情况下的隔热保温性能。
研究发现，硅微粉在高温并含有铝元素的情况下，会向莫来石方向进行反应和转变，莫来石是一种优秀的耐火材料，因此硅微粉的加入进一步提高了所述二氧化硅气凝胶颗粒的耐高温能力。
在一些实施例中，硅微粉的粒径是800-8000目、1000-2000目、2000-3000目、3000-4000目、4000-5000目、5000-6000目、6000-7000目、7000-8000目、1000-1500目、1500目-3000 目，或10-800nm、10-100nm、50-200nm、100-400nm、300-800nm。优选的粒径是800-1000目、1000-1200目、1000-3000目。
在一些实施例中，硅微粉的添加量(质量百分比)是3-25％、1-10％、3-15％、5-20％、5-25％、10-25％，优选的添加量是2-10％、3-8％、3-6％。示例性地，非晶态硅微粉的添加量(质量百分比)为1-20％、1-15％、2-10％、3-8％。优选的粒径可以更好的促进硅、铝和氧键的结合，使得结构更加稳定。优选的添加量可以更好的提升气凝胶颗粒在高温的抗收缩的能力，同时保持较高的隔热性能与机械强度。
在一些实施例中，所述颗粒为外部包裹所述稀土掺杂二氧化硅气凝胶层的氧化铝颗粒、外部包括所述稀土掺杂二氧化硅气凝胶层的硅酸铝颗粒、外部包裹氧化铝保护层的稀土掺杂二氧化硅气凝胶颗粒中的至少一种。
在一些实施例中，氧化铝保护层的厚度范围是1μm-500μm。
在一些实施例中，稀土掺杂二氧化硅气凝胶包裹层的厚度范围是0.5μm-250μm。
[二氧化硅气凝胶颗粒的制备方法]
本发明还提供上述二氧化硅气凝胶颗粒的制备方法，其包括以下步骤：
先制备所述稀土掺杂二氧化硅气凝胶颗粒，然后与铝氧化物和/或铝盐混合，制备得到所述外壳是铝氧化物和/或铝盐而内核是上述的稀土掺杂二氧化硅气凝胶的颗粒；
或者，采用上述的稀土掺杂二氧化碳气凝胶的制备方法制备所述气凝胶，其中在所述步骤3)的制备凝胶的过程中加入铝氧化物和/或铝盐颗粒，从而可以制备得到所述外壳是上述的稀土掺杂二氧化硅气凝胶而内核是铝氧化物和/或铝盐的颗粒。
本实施例的技术方案，XRF测试表明Clˉ的杂质含量为0.03wt％-0.15wt％。使用稀土硝酸盐进行掺杂，可以减少气凝胶产品中的Clˉ含量，降低氯离子带来的腐蚀性，有利于气凝胶的应用。
下面通过实施例结合附图进一步地说明本发明中的技术方案，这些实施例仅是用来提供对本发明的进一步理解，且作为构成说明书的一部分，与上述的附图一起用于解释本发明，但并不构成对本发明的限制。此外应理解，在阅读了本发明讲授的内容之后，本领域技术人员可以对本发明作各种改动或修改，这些等价形式同样落于本申请所限定的范围。
实施例1
本实施例包括以下步骤：
(1)在三口烧瓶中加入20.8g TEOS、55.2g无水乙醇以及5.4g H 2O，机械搅拌15min，通过恒压漏斗向其中滴加3.65g质量分数为0.05wt％的盐酸乙醇稀释液，搅拌120min后室温下密封静置24h，获得摩尔比n(TEOS):n(C 2H 5OH):n(H 2O)＝1:12:3的SiO 2溶胶。
(2)将34.8g Y(NO 3) 3·4H 2O粉末溶于10.8g水中，50℃加热反应30min，冷却至室温后得到Y(NO 3) 3溶液。
(3)称取0.684g步骤(2)中所得物料，缓慢滴入9.31g SiO 2溶胶中，磁力搅拌30min。
(4)在步骤(3)所得物料中滴入氨水乙醇稀释液，搅拌均匀后静置凝胶。
(5)将上述Y-SiO 2凝胶密闭静置老化24h后进行超临界干燥，以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa。以1℃/min的升温速率将釜内温度升至270℃，保温2h至釜内压力为10MPa。打开水冷装置，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到Y-SiO 2气凝胶。
(6)本实施例获得的块状Y-SiO 2气凝胶的宏观图如图1所示，获得的气凝胶密度为0.17g/cm 3，其比表面积为648.17m 2/g，平均孔径为20.45nm。其N 2吸附-脱附曲线和孔径分布图如图2所示，气凝胶微观结构如图3所示。
另外，经测试，气凝胶中的卤素离子含量为0.09％。
另外，测试了实施例1的稀土掺杂二氧化硅气凝胶与常规二氧化硅气凝胶在高温下的导热率，测试结果列于表1中。从中可见，本发明的气凝胶相较于常规二氧化硅气凝胶具有显著提高的高温下的导热性能。
表1本发明气凝胶与常规气凝胶的高温下的导热率测试结果
  实施例1的稀土掺杂二氧化硅气凝胶 常规二氧化硅气凝胶
温度(℃) 导热率(W/m·K) 导热率(W/m·K)
300 0.037 0.038
400 0.045 0.049
500 0.051 0.061
600 0.060 ＞0.1
700 0.065 ＞0.1
800 0.070 ＞0.1
900 0.078 ＞0.1
1000 0.082 ＞0.2
1100 0.095 ＞0.3
实施例2
本实施例包括以下步骤：
(1)在三口烧瓶中加入20.8g TEOS、32.2g无水乙醇以及5.4g H 2O，机械搅拌15min，通过恒压漏斗以6s/滴的速度向其中滴加3.65g质量分数为0.05wt％的盐酸乙醇稀释液，搅拌120min后室温下密封静置24h，获得摩尔比n(TEOS):n(C 2H 5OH):n(H 2O)＝1:7:3的SiO 2溶胶。
(2)将34.8g Y(NO 3) 3·4H 2O粉末溶于10.8g水中，50℃加热反应30min，冷却至室温后得到Y(NO 3) 3溶液。
(3)称取0.137g步骤(2)中所得物料，缓慢滴入12.8g SiO 2溶胶中，磁力搅拌30min。
(4)在步骤(3)所得物料中滴入氨水乙醇稀释液，搅拌均匀后静置凝胶。
(5)将上述Y-SiO 2凝胶密闭静置老化24h后进行超临界干燥，以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa。以1℃/min的升温速率将釜内温度升至270℃，保温2h至釜内压力为8MPa。打开水冷装置，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到Y-SiO 2气凝胶。
(6)本实施例获得的块状Y-SiO 2气凝胶的密度为0.29g/cm 3，其比表面积为861.17m 2/g，平均孔径为10.29nm。
另外，经测试，气凝胶中的卤素离子含量为0.11wt％。
实施例3
本实施例的制备方法包括以下步骤：
(1)在三口烧瓶中加入20.8g TEOS、92g无水乙醇以及5.4g H 2O，机械搅拌15min，通过恒压漏斗以6s/滴的速度向其中滴加3.65g质量分数为0.05wt％的盐酸乙醇稀释液，搅拌120min后室温下密封静置24h，使得水解反应充分而缓慢的进行，获得摩尔比n(TEOS):n(C 2H 5OH):n(H2O)＝1:20:3的SiO 2溶胶。
(2)将34.8g Y(NO 3) 3·4H 2O粉末溶于10.8g水中，50℃加热反应30min，冷却至室温后得到Y(NO 3) 3溶液。
(3)称取0.228g步骤(2)中所得物料，缓慢滴入12.2g SiO 2溶胶中，磁力搅拌30min。
(4)在步骤(3)所得物料中滴入氨水乙醇稀释液，搅拌均匀后静置凝胶。
(5)将上述Y-SiO 2凝胶密闭静置老化24h后进行超临界干燥，以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa。以1℃/min的升温速率将釜内温度升至270℃，保温4h至釜内压力为8MPa。打开水冷装置，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到Y-SiO 2气凝胶。
(6)本实施例获得的块状Y-SiO 2气凝胶的密度为0.10g/cm 3，其比表面积为844.28m 2/g，平均孔径为13.22nm。
另外，经测试，气凝胶中的卤素离子含量为0.13wt％。
实施例4
本实施例包括以下步骤：
(1)在三口烧瓶中加入20.8g TEOS、78.2g无水乙醇以及5.4g H 2O，机械搅拌12min，通过恒压漏斗向其中滴加1.825g质量分数为0.1wt％的盐酸乙醇稀释液，搅拌110min后室温下密封静置22h，获得摩尔比n(TEOS):n(C 2H 5OH):n(H 2O)＝1:17:3的SiO 2溶胶。
(2)将34.8g Y(NO 3) 3·4H 2O粉末溶于10.8g水中，45℃加热反应35min，冷却至室温后得到Y(NO 3) 3溶液。
(3)称取0.684g步骤(2)中所得物料，缓慢滴入11.8g SiO 2溶胶中，磁力搅拌30min。
(4)在步骤(3)所得物料中滴入氨水乙醇稀释液，搅拌均匀后静置凝胶。
(5)将上述Y-SiO 2凝胶密闭静置老化22h后进行超临界干燥，以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa。以1℃/min的升温速率将釜内温度升至270℃，保温4h至釜内压力为10MPa。打开水冷装置，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到Y-SiO 2气凝胶。
另外，经测试，气凝胶中的卤素离子含量为0.15wt％。
实施例5
本实施例提供了一种含有稀土、硅微粉和遮光剂的二氧化硅气凝胶，其制备方法包括以下步骤：
(1)在三口烧瓶中加入20.8g TEOS、92g无水乙醇、5.4g H 2O、1g硅微粉(1000目)，超声分散30分钟，机械搅拌15min，通过恒压漏斗以6s/滴的速度向其中滴加3.65g质量分数为0.05wt％的盐酸乙醇稀释液5搅拌120min后室温下密封静置24h，使得水解反应充分而缓慢的进行，获得摩尔比n(TEOS):n(C 2H 5OH):n(H 2O)＝1:20:3的SiO 2溶胶。
(2)将34.8g Y(NO 3) 3·4H 2O粉末溶于10.8g水中，50℃水浴反应30min，冷却至室温后得到Y(NO 3) 3溶液。
(3)称取0.228g步骤(2)中所得物料，缓慢滴入12.2g SiO 2溶胶中，磁力搅拌30min。
(4)在步骤(3)所得物料中滴入氨水乙醇稀释液，搅拌均匀后静置凝胶。
(5)使用乙醇溶剂对凝胶进行溶剂置换。
(6)将上述Y-SiO 2凝胶密闭静置老化24h后进行超临界干燥，以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa。以1℃/min的升温速率将釜内温度升至270℃，保温2h至釜内压力为12MPa。打开水冷装置，压力降低的速率为3-4MPa/h，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到Y-SiO 2气凝胶。本实施例得到的硅微粉稀土掺杂二氧化硅气凝胶与常规二氧化硅气凝胶参数对比如下，硅微粉稀土掺杂二氧化硅气凝胶在高温情况下(＞600℃)的隔热性能明显优于常规二氧化硅气凝胶。
硅微粉稀土掺杂二氧化硅气凝胶与常规二氧化硅气凝胶参数表
  硅微粉稀土掺杂二氧化硅气凝胶 常规二氧化硅气凝胶
温度(℃) 导热率(W/m·K) 导热率(W/m·K)
300 0.039 0.038
400 0.044 0.0490
500 0.052 0.061
600 0.059 ＞0.1
700 0.062 ＞0.1
800 0.068 ＞0.1
900 0.075 ＞0.1
1000 0.081 ＞0.2
实施例6
本实施例提供了一种含有稀土、硅微粉、遮光剂和纤维的二氧化硅气凝胶，其制备方法包括以下步骤：
(1)在三口烧瓶中加入20.8g TEOS、92g无水乙醇、5.4g H 2O、1g硅微粉(1000目)，超声分散30分钟，机械搅拌15min，通过恒压漏斗以6s/滴的速度向其中滴加3.65g质量分数为0.05wt％的盐酸乙醇稀释液，搅拌120min后室温下密封静置24h，使得水解反应充分而缓慢的进行，获得摩尔比n(TEOS):n(C 2H 5OH):n(H 2O)＝1:20:3的SiO 2溶胶。
(2)将34.8g Y(NO 3) 3·4H 2O粉末溶于10.8g水中，50℃水浴反应30min，冷却至室温后得到Y(NO 3) 3溶液。
(3)称取0.228g步骤(2)中所得物料，缓慢滴入12.2g SiO 2溶胶中，磁力搅拌30min。
(4)在步骤(3)所得物料中滴入氨水乙醇稀释液，搅拌均匀后，并将其浇筑至纤维预制件中，之后静置36h获得凝胶。纤维预制件是玻璃纤维预制件。
(5)使用乙醇溶剂对凝胶进行溶剂置换。
(6)将上述Y-SiO 2凝胶密闭静置老化24h后进行超临界干燥，以乙醇为超临界干燥的介质，预充N 2至釜内压力为2MPa。以1℃/min的升温速率将釜内温度升至270℃，保温2h 至釜内压力为12MPa。打开水冷装置，压力降低的速率为3-4MPa/h，缓慢释放釜内压力至常压后，通入N 2吹扫釜内，冷却至室温后得到Y-SiO 2气凝胶。
实施例7
本实施例提供一种包含稀土、硅微粉、遮光剂、纤维的二氧化硅气凝胶颗粒，其制备方法，包括以下步骤：
(1)硅溶胶制备：将硅源、水、醇溶剂混合制备硅溶胶，还可以向硅溶胶中加入水解催化剂加速硅源水解，更快获得硅溶胶。硅源可选用硅酸钠、正硅酸乙酯、正硅酸甲酯、四丙氧基硅烷、四丁氧基硅烷、二甲基二甲氧基硅烷或二甲基二乙氧基硅烷或其组合。水解催化剂可选用盐酸、草酸、硝酸、硫酸、磷酸或其组合。醇溶剂可选用甲醇、乙醇或其组合。
(2)铝溶胶制备：铝源、水混合，并加入乙酰乙酸乙酯，将异丙醇铝水解，得到稳定的氧化铝溶胶。进一步的，铝源与水的摩尔比是1:80-120，水解温度是60-80℃，水解时间2-4h。
(2)稀土硅铝溶胶制备：将稀土化合物制备成稀土溶液，并将稀土溶液与硅溶胶、铝溶胶混合，得到稀土硅铝溶胶。硅与铝的摩尔比为1:0.1-0.5。稀土化合物可选用钇金属盐、钪金属盐、钕金属盐、镱金属盐；钇金属氧化物、钪金属氧化物、钕金属氧化物、镱金属氧化物。
进一步的，钇金属盐可以是硝酸钇、氯化钇、草酸钇、碳酸钇；钪金属盐可以是硝酸钪、氯化钪、草酸钪、碳酸钪；钕金属盐可以是硝酸钕、氯化钕、草酸钇、碳酸钕；镱金属盐可以是硝酸镱、氯化镱、草酸镱、碳酸镱。
进一步的，稀土溶液中可以包含一种或一种以上上述稀土化合物。
(3)凝胶制备：向稀土硅溶胶中加入凝胶催化剂使得稀土硅铝溶胶转变为稀土掺杂凝胶，凝胶催化剂是氨水、二甲基甲酰胺、氨水乙醇稀释液等。
(4)干燥：对稀土掺杂凝胶进行干燥，得到稀土掺杂硅铝复合气凝胶。干燥的方法可以是常温常压干燥、临界干燥、超临界干燥等。临界干燥、超临界干燥的干燥介质可选用CO 2、甲醇、乙醇。
常温常压干燥的条件是，分别在60、80和120℃干燥2h，最后得白色SiO 2气凝胶粉末。
二氧化碳超临界干燥的条件是，在溶剂是乙醇的情况下，在5℃，5.5MPa下用液态二氧化碳浸泡3天，并放出置换出的乙醇；然后升温至35℃，10.5MPa并保持3h，然后以0.5MPa/h的速度缓慢泄压至常压，即得到气凝胶块体。
乙醇超临界干燥的条件是，按预设程序升温升压至临界点后，在恒定温度状态下，以缓慢的速度释放反应釜内部的流体，直至内外压力平衡。升温前可以使用N 2预先充满反应釜，预充N 2的压力为1-4Mpa，升温至240℃以上，升温速率0.5-2℃/min，当压力超过8Mpa后，开启冷却装置，缓慢泄压，泄压至常压后通入N 2吹扫反应釜，待冷却至室温后，得到稀土掺杂气凝胶。
稀土掺杂硅铝复合气凝胶在800℃情况下的导热系数范围是0.01W/m·K-0.28W/m·K，稀土掺杂硅铝复合气凝胶起始融化温度是1100℃。绝热层的导热系数是0.01W/m·K-0.045W/m·K。
本发实施例在气凝胶中引入耐火、耐高温能力更强的含铝物质，解决了二氧化硅气凝胶在高温情况下会发生内部二氧化硅微观结构坍塌的问题。
实施例8
本发明还提供一种防排烟风管，所述防排烟风管包括金属管道，金属管道的内壁和/或外壁设置有热屏蔽层，所述热屏蔽层包括绝热层，所述绝热层中包括上述的保温隔热材料或上述的保温隔热复合材料，或者，所述绝热层包含骨架、填料、抗收缩添加剂和耐高温添加剂。
根据本发明的一种实施方式，所述热屏蔽层还包括导热层、热反射层中的至少一种。
根据本发明的一种实施方式，所述填料包括二氧化硅气凝胶、硅酸铝气凝胶、氧化铝气凝胶、复合二氧化硅气凝胶、稀土掺杂二氧化硅气凝胶的至少一种。示例性地，填料具有核壳结构，其中，外壳是硅酸铝和/或氧化铝气凝胶、内核是二氧化硅气凝胶，或者外壳是二氧化硅气凝胶、内核是硅酸铝和/或氧化铝气凝胶。或者，所述气凝胶可以是二氧化硅与氧化铝复合的二氧化硅/氧化铝复合气凝胶。
进一步地，所述骨架由纤维材料制成，纤维材料可以是硅酸铝纤维、氧化铝纤维、玻璃纤维、莫来石纤维、SiO 2陶瓷纳米纤维的至少一种。
进一步地，所述耐高温添加剂可以是硅酸铝、石英粉、硅微粉等。
进一步地，所述防排烟风管具备快速连接功能，具体的，所述防排烟风管由前风管单元和后风管单元快速拼接而成。每个风管单元的主体结构包括金属主体框架、与框架内壁贴合的内壁热屏蔽层，与框架外壁贴合的外壁热屏蔽层，以及外壁热屏蔽层外侧相贴合的耐火密封胶。其中，所述内壁热屏蔽层、金属主体框架、外壁热屏蔽层、外侧耐火密封胶依次覆盖连接，连接方式可以为铆钉固定、粘连等物理或化学连接方法。内壁热屏蔽层与外壁热屏蔽 层可由绝热层以及导热层和热反射层中的单层或多层构成。此外，为使风管单元间能够紧密相连，实现密闭、隔热、防止热桥的功能，每个风管单元的两端分别设有延伸层与接收区域。
进一步地，所述防排烟风管包括前风管、后风管、安装座、定位杆和定位筒；所述前风管一端可拆卸连接有所述后风管；所述安装座对称设于所述前风管和所述后风管的侧面，所述定位杆和所述定位筒对应设于两侧安装座的相对侧面，且所述定位杆和所述定位筒滑动配合；所述前风管内壁和/或外壁设置有热屏蔽层，所述后风管内壁和/或外壁设置有热屏蔽层；所述热屏蔽层包括绝热层以及导热层、热反射层中的至少一种；所述绝热层与所述前风管、后风管的内壁和/或外壁贴合。
进一步地，所述防排烟风管包括前风管、后风管；所述前风管一端可拆卸连接有所述后风管；所述前风管、后风管两端分别设有角钢法兰；所述前风管内壁和/或外壁设置有热屏蔽层，所述后风管内壁和/或外壁设置有热屏蔽层；所述热屏蔽层包括绝热层以及导热层和热反射层中的至少一种；所述绝热层与所述前风管、后风管的内壁和/或外壁贴合。
优选的，上述连接组件包括：金属或其他耐高温材料制成的环绕式固定箍120、螺栓121、螺母122，如图7所示。其中环绕式固定箍120还包括限位孔，环绕式固定箍120的宽度不小于风管延伸出的外壁热屏蔽层200及的长度。
两个风管单元连接后的固定方式可以为：环绕式固定箍120覆盖住两个风管单元金属管道100与热屏蔽层200连接的缝隙，螺栓121穿过相应的限位孔，并用螺母122旋紧固定。
上述技术方案，提供了一种可以快速连接固定、具有隔热功能的防排烟风管结构。实现了防排烟风管之间的快速连接，提高了工作效率，同时保证了风管的防排烟密闭性及耐火性能不会下降，实用性较强。本技术方案可实现两个风管之间的快速连接，提高了工作效率，同时保证了风管的防排烟密闭性及耐火性能不会下降，实用性较强。
进一步地，本发明提供了一个技术方案，发明人通过对复合的二氧化硅/硅酸铝气凝胶颗粒或二氧化硅/氧化铝气凝胶颗粒中的二氧化硅气凝胶部分做了进一步的改性和优化，虽然二氧化硅气凝胶与含铝气凝胶进行了复合，但是在高温情况下二氧化硅气凝胶部分本身也有可能出现收缩坍塌的问题，发明人向二氧化硅气凝胶中加入抗收缩添加剂(例如硅微粉)，通过硅微粉在高温下的晶型变化、体积变化，可以抑制和减少二氧化硅气凝胶的收缩坍塌问题，进一步提高复合二氧化硅/硅酸铝气凝胶颗粒或复合二氧化硅/氧化铝气凝胶颗粒的耐温性能，进一步提高复合气凝胶的耐温性能，增强绝热层性能从而改善防排烟耐火通风管道的高温表现。
应用增强的气凝胶材料于防排烟风管中，如加入了复合二氧化硅/硅酸铝气凝胶颗粒或复合二氧化硅/氧化铝气凝胶颗粒或稀土掺杂二氧化硅气凝胶的绝热层，可以在实现较低的传热系数同时承受高温，使得气凝胶材料可以应用于防排烟风管的领域中，增强防排烟风管的耐热能力，在火灾发生时候使得防排烟风管正常的发挥作用。应用气凝胶隔热材料于防排烟风管中，还可以减少隔热材料的空间占用。
本技术方案还可以解决现有技术中防排烟风管使用的隔热材料会出现吸水导致隔热结构坍塌、寿命短，同时由于导热系数高的原因导致占用空间较大的问题。在实际中火场风管在局部受热的情况下，还会出现风管结构变化坍塌、风管出现缺陷，导致管内风压变化、漏风，也会使得风管排风性能下降。气凝胶的体积在高温情况下(800摄氏度以上)会发生体积收缩的现象，导致结构变化而降低隔热保温性能。本发实施例要解决的技术问题是绝热层材料在高温情况下，会发生内部二氧化硅微观结构收缩和坍塌的问题，采用的手段是向材料中添加硅微粉材料抑制和抵消在气凝胶材料在高温下收缩和坍塌的问题。
进一步地，发明人通过对绝热层中的填料进行了改进和优化，合成和使用了由二氧化硅与氧化铝复合的二氧化硅/氧化铝复合气凝胶、稀土掺杂二氧化硅气凝胶，上述气凝胶中的二氧化硅部分提供优秀的隔热能力，氧化铝部分提供优秀的耐温性能，以及稀土提高了耐温能力。氧化铝与二氧化硅分子结合，微观上可以抑制和降低二氧化硅分子在高温情况下的收缩、融化和晶型变化，宏观情况下减少绝热层(气凝胶毡)的掉粉情况，使得填料在高温情况下仍有隔热性能，以及以维持比较好的物理化学性能，满足使用要求。
进一步地，发明人通过对二氧化硅气凝胶做了改性和优化，改进了二氧化硅气凝胶材料的内部结构，将耐火性能更好但隔热性能略差的铝氧化物/铝盐材料与二氧化硅气凝胶结合，形成外壳是铝氧化物/铝盐而内核是二氧化硅气凝胶的复合二氧化硅气凝胶颗粒，或者形成外壳是二氧化硅气凝胶而内核是铝氧化物/铝盐的复合二氧化硅气凝胶颗粒。这样能够使得二氧化硅气凝胶在高温情况下保持稳定，同时复合的颗粒具有较好的隔热性能，还可以维持比较好的物理化学性能，将其应用于绝热层可以满足防排烟通风管道的使用要求。
进一步的，发明人通过对二氧化硅气凝胶进行了稀土掺杂，具体的，由于稀土的掺杂可提高二氧化硅气凝胶的使用温度，扩展气凝胶在高温极端条件下应用，能控制气凝胶的密度、微观结构，进一步通过控制其中阴离子的含量，从而控制气凝胶的导热系数及其高温下的性能。可以掺杂的稀土元素包括钇、钪、钕和镱。
本技术方案解决了气凝胶无法达到防排烟风管耐温防火要求的问题，同时使绝热层具备良好的保温、消声吸音、防潮、漏风量小、使用寿命长、性价比合理等特点。发明人还发现虽然二氧化硅气凝胶的隔热性能非常好，但是其耐高温性能存在一定程度的缺陷，传统二氧化硅气凝胶在超过600℃开始融化，在800℃以上纳米孔道开始坍塌，在温度高于1000℃场合已基本失去保温效果，无法满足防排烟风管标准的要求。
本技术方案还可以解决现有技术中防排烟风管使用的隔热材料会出现吸水导致隔热结构坍塌、寿命短，同时由于导热系数高的原因导致占用空间较大的问题。在实际中火场风管在局部受热的情况下，还会出现风管结构变化坍塌、风管出现缺陷，导致管内风压变化、漏风，也会使得风管排风性能下降。
实施例9
本发明还提供一种防排烟耐火通风管道，所述防排烟耐火通风管道包括金属管道，金属管道内壁和/或外壁设置有热屏蔽层，热屏蔽层包括高温膨胀层和绝热层，还包括导热层、热反射层中的至少一种，所述绝热层采用上述的保温隔热材料或保温隔热复合材料。
根据本发明的一种实施方式，所述高温膨胀层包括高温发泡剂、多功能碳颗粒、稳定剂。高温发泡剂的发泡温度大于500℃，高温发泡剂是碳化硅粉末或颗粒。多功能碳颗粒可以是石墨、石墨烯。稳定剂是二氧化锰。高温膨胀层的厚度是1-5mm，膨胀后的厚度是20-100mm。一种优选的方案是还包括气凝胶颗粒，以提升高温膨胀层的隔热性能。气凝胶颗粒的添加的质量比例是3-5％。高温膨胀层还可以包含减水剂，减水剂为三聚磷酸钠或六偏磷酸钠。
研究发现，高温膨胀层在遇到高温时候碳化硅会膨胀发泡，高温膨胀层的厚度增加、导热率降低，同时内部添加的多功能碳颗粒在高温情况下兼具遮光剂的作用，减少高温情况下的热辐射。保护防排烟风管在高温情况下的结构稳定。多功能碳颗粒在高温膨胀层未发泡情况下(500℃以下)，由于还处于紧密压合状态，其具有比较好的导热功能，可以快速分散热量，降低局部过热的情况。当温度超过500℃以上时，通过导热分散也无法使得整体温度低于排烟风管可耐受的温度时候，高温膨胀层膨胀发泡，其中的多功能碳颗粒由于被分散不在紧密连接导热性能消失，高温膨胀层由导热功能变为具有高温隔热性能的功能层。同时这些多功能碳颗粒在这种状况下，具有对红外线的吸收作用，起到了遮光剂的作用，进一步提高了高温状态下的隔热性能。
实施例10
在本发明所涉及的一个技术方案中，提供一种具有可用于快速连接固定结构的防排烟风管，风管通过风管单元拼接而成。
其中，每个风管单元的主体结构如图7和图8所示，包括金属主体框架、与框架内壁贴合的内壁热屏蔽层，与框架外壁贴合的外壁热屏蔽层，以及外壁热屏蔽层外侧相贴合的耐火密封胶。其中，所述内壁热屏蔽层、金属主体框架、外壁热屏蔽层、外侧耐火密封胶依次覆盖连接，连接方式可以为铆钉固定、粘连等常见的物理或化学连接方法。内壁热屏蔽层与外壁热屏蔽层可由绝热层、导热层、反射层中的单层或多层构成。此外，为使风管单元间能够紧密相连，实现密闭、隔热、防止热桥的功能，每个风管单元的两端分别设有延伸层与接收区域。
优选的，金属主体框架为彩钢板。
优选的，金属主体框架表面涂覆有抗菌涂层。
其中延伸层是指在一个风管单元的一端，沿平行于管壁方向从主体结构向外延伸的结构层。接收区域是指在风管单元上延伸层的另一端，为与另一个风管单元延伸层相连接所预留的区域，当两个风管单元相连接时，应为有延伸层的一端与有接收区域的一端相连接，连接后，两个风管单元在连接处可以紧密贴合，并在连接处通过连接组件固定。视延伸层的结构，在有接收区域的一端，风管单元的结构可以根据延伸层的结构进行单层或多层的延伸，以便于在风管单元间连接时可与延伸层贴合，该部分在接收端进行延伸的结构，定义为延伸接收层。
优选的，有两个待连接的风管单元，两个风管的结构相同，结构均包括风管单元主体、延伸层与接收区域，不包括延伸接收层。其中风管单元主体由金属管道、金属管道内壁热屏蔽层和金属管道外壁热屏蔽层构成，延伸层由外壁热屏蔽层沿平行于管壁方向进行向外延伸构成，延伸层沿平行于管壁方向的延伸长度与接收区域沿平行于管壁方向的预留宽度相同。
连接方式为：一个风管单元有延伸层的一端与另一个风管单元有接收区域的一端相连接，且两个风管单元的金属管道相接触，所延伸出的外壁热屏蔽层相接触，一个风管单元有延伸层的一端所延伸出的外壁热屏蔽层，覆盖另一个风管单元有接收区域的一端的金属管道。连接后，两个风管单元贴合紧密，并通过连接组件固定。
优选的，上述连接组件包括：金属或其他耐高温材料制成的环绕式固定箍、螺栓、螺母。其中环绕式固定箍还包括限位孔，环绕式固定箍的宽度不小于风管延伸出的外壁热屏蔽层及的长度。
两个风管单元连接后的固定方式可以为：环绕式固定箍覆盖住两个风管单元金属管道与热屏蔽层连接的缝隙，螺栓穿过相应的限位孔，并用螺母旋紧固定。
风管可以是矩形的，风管长边边长b≤500mm，支吊架间距d≤2800mm；500mm≤风管长边边长b≤1000mm，支吊架间距d≤2400mm；1000mm≤风管长边边长b≤2000mm，支吊架间距d≤1400。
矩形风管尺寸可以是120mm、160mm、200mm、250mm、320mm、400mm、500mm、630mm、800mm、1000mm、1250mm、1600mm、2000mm、2500mm、3000mm、3500mm、4000mm。
优选的，两个待连接的风管单元在两端分别设有用于连接的角钢法兰结构，法兰由金属或其他耐高温材料制成，当两个风管单元连接后，位于两个风管单元连接缝两侧的两个角钢法兰结构可以紧密贴合，并通过连接组件固定。
优选的，上述连接组件包括：金属或其他耐高温材料制成的多个螺栓及螺母。连接方式为螺母穿过相应的角钢法兰上的限位孔，并通过螺栓固定锁紧。
实施例11
常规防排烟风管为了实现隔温、耐高温的性能，通常使用更厚的隔温材料，更高等级的耐火材料，阻断热量传递，从而达到隔温、耐高温的要求。发明人发现，防排烟风管的在紧急情况下，往往是局部受到高温影响，从而影响到其结构稳定性。防排烟的其余大部分位置，并没有达到设计极限而出现性能问题。因此发明人认为，可以使用导热而隔热、耐温的方法，将局部的高温扩散至防排烟风管其余的位置，降低局部的高温从而使得防排烟风管可以承受更高的温度。
在本发明所涉及的一个技术方案中，提供一种防排烟风管，防排烟风管包括金属管道100，金属管道100内壁和/或外壁设置有热屏蔽层200，热屏蔽层200包括绝热层210、导热层220、热反射层230的至少一种。绝热层可以使用上述保温隔热材料或上述保温隔热复合材料。
导热层220可以是金属导热板，如铜、铝等高导热性能的金属材料；还可以是导热金属结构，如中空的导热夹层；还可以是设置有热管的装置的导热层220。
其中导热层220、热反射层230、绝热层210依次叠加构成热屏蔽层200。另外一种布置方式是热反射层230、导热层220、绝热层210依次叠加构成热屏蔽层200。绝热层210与金属管道100内壁和/或外壁贴合。
一种防排烟风管包括前风管140和后风管150，前风管140一端可拆卸连接有后风管150。
进一步地，防排烟风管还包括安装座160、定位杆161和定位筒162，安装座160对称设于前风管140和后风管150的侧面，所述定位杆161和定位筒162对应设于两侧安装座160的相对侧面，且定位杆161和定位筒162滑动配合，如图8所示。
进一步地，前风管和后风管之间设有第一连接组件和第二连接组件；第一连接组件包括限位孔、导孔、限位杆和螺帽，所述限位孔贯穿竖槽的上下两端，所述导孔贯穿竖方杆的上下两端，且导孔与限位孔对应，所述限位杆与导孔对应配合，所述螺帽螺纹连接在限位杆的顶端。
实施例12
常规防排烟风管为了实现隔温、耐高温的性能，通常使用更厚的隔温材料，更高等级的耐火材料，阻断热量传递，从而达到隔温、耐高温的要求。发明人发现，防排烟风管的在紧急情况下，往往是局部受到高温影响，从而影响到其结构稳定性。防排烟的其余大部分位置，并没有达到设计极限而出现性能问题。因此发明人认为，可以使用导热而隔热、耐温的方法，将局部的高温扩散至防排烟风管其余的位置，降低局部的高温从而使得防排烟风管可以承受更高的温度。
在本发明所涉及的一个技术方案中，提供一种防排烟风管，防排烟风管包括金属管道，金属管道内壁和/或外壁设置有热屏蔽层，热屏蔽层包括绝热层、导热层、热反射层的至少一种。绝热层可以使用上述保温隔热材料或上述保温隔热复合材料。
导热层可以是金属导热板，如铜、铝等高导热性能的金属材料；还可以是导热金属结构，如中空的导热夹层；还可以是设置有热管的装置的导热层。
其中导热层、热反射层、绝热层依次叠加构成热屏蔽层。另外一种布置方式是热反射层、导热层、绝热层依次叠加构成热屏蔽层。绝热层与金属管道内壁和/或外壁贴合。
导热层的形式包括硅胶散热膜、石墨散热膜、金属导热板、热管式导热板。金属导热板的材料可以是铜板、铝板。导热层的形式还可以是具有导热结构的通道，如双层中空金属导热板。导热层的在800℃情况下的导热系数范围是20W/m·K-50W/m·K。
在防排烟风管设置导热层可以强化防排烟风管的导热、散热性能，防止局部高温，可以避免内部的二氧化硅气凝胶颗粒在高温如600℃以上融化，使得绝热层在高温情况下仍能保维持结构稳定，满足防排烟风管的使用要求。
发明人还认为，可以在防排烟风管内部设置吸热层的方式降低局部高温，从而使得防排烟风管可以承受更高的温度。
在本发明所涉及的一个技术方案中，提供一种防排烟风管，防排烟风管包括金属管道，金属管道内壁和/或外壁设置有热屏蔽层，热屏蔽层包括绝热层，绝热层可以使用上述保温隔热材料或上述保温隔热复合材料，热屏蔽层还可以包括导热层、热反射层、吸热层的至少一种。
一种优选的方式是导热层、热反射层、吸热层、绝热层依次叠加构成热屏蔽层。其中导热层、热反射层、吸热层、绝热层依次叠加构成热屏蔽层。另外一种布置方式是热反射层、吸热层、绝热层依次叠加构成热屏蔽层。绝热层与金属管道内壁和/或外壁贴合。
吸热层由储热材料构成，储热材料可以是相变材料、受热挥发材料等，还可以是预置的降温材料如预置水仓、预置二氧化碳仓等，在遇到高温时候可以释放装载的水、二氧化碳等降温载体，吸收热量。相变材料可以吸收热量并保持温度恒定，从而在局部有高温的情况下，吸收热量产生相变而温度不升高，进而保护绝热层的气凝胶结构不坍塌，使得绝热层维持隔热效果，从而使得整个热屏蔽层在高温下仍能保持隔温效果。
相变材料为融盐类，熔融盐包括碳酸盐、氯化盐、氟化盐。
在防排烟风管设置吸热层可以降低防排烟风管的温度，防止局部高温，可以避免内部的二氧化硅气凝胶颗粒在高温如600℃以上融化，使得气凝胶绝热达到使用要求。
绝热层、导热层、热反射层、吸热层通过粘合、热压的方式相互固定。热屏蔽层外部还可以使用玻纤布、铝箔层包裹，防止填料碎裂掉粉的现象发生。
本发明以正硅酸乙酯和稀土硝酸盐为原料，乙醇为溶剂，酸和碱为催化剂，采用溶胶凝胶法制备稀土掺杂二氧化硅湿凝胶，经溶剂置换、乙醇超临界干燥后得到块状稀土掺杂二氧化硅气凝胶。该方法通过在二氧化硅气凝胶中掺入稀土元素，可提高二氧化硅气凝胶的使用温度，扩展气凝胶在高温极端条件下的应用。通过控制乙醇含量、稀土掺杂量及成型工艺等，能控制气凝胶的密度、微观结构，从而控制气凝胶的导热系数。该方法工艺简单易行、生产效率高，有利于大规模生产。
以上所述实施例仅为本发明的较佳实施例，但本发明的实施方式不受上述实施例的限制，依据本发明的专利范围及说明书内容所做的等效变换、修饰、替代等行为，皆应仍属本发明涵盖的范围之内。

Claims (25)

  1. 一种稀土掺杂二氧化硅气凝胶，其特征在于，所述气凝胶为块状稀土掺杂二氧化硅气凝胶，所述气凝胶中的卤素离子含量不高于0.2wt％。
  2. 根据权利要求1所述的稀土掺杂二氧化硅气凝胶，其特征在于，所述稀土选自钇Y、钪Sc、和La系稀土金属中的至少一种；
    和/或，所述稀土在所述气凝胶中以REE-O-Si键形式存在；
    和/或，所述气凝胶中，所述稀土元素与Si元素和氧元素一起构成网状非晶体结构；和/或，所述稀土元素均匀分布在所述网状非晶体结构中；
    和/或，所述气凝胶具备下述性能中的至少一种：
    1)密度为0.08～0.35g/cm 3；
    2)比表面积为640～880m 2/g；
    3)平均孔径为10nm～22nm；
    4)疏水角为85°～130°。
  3. 根据权利要求1或2所述的稀土掺杂二氧化硅气凝胶，其特征在于，所述气凝胶中还包括硅微粉、遮光剂、纤维和铝中的至少一种。
  4. 根据权利要求3所述的稀土掺杂二氧化硅气凝胶，其特征在于，所述硅微粉的粒径是600-1500目。
  5. 一种权利要求1-4任一项所述稀土掺杂二氧化硅气凝胶的制备方法，其特征在于，所述方法包括以下步骤：
    1)制备硅溶胶：将硅源、水、醇溶剂混合制备硅溶胶；
    2)制备稀土硅溶胶：配置稀土化合物溶液，并将稀土化合物溶液与上述硅溶胶混合，得到稀土硅溶胶；所述稀土化合物为稀土金属硝酸盐、稀土金属草酸盐、稀土金属碳酸盐或稀土金属氧化物中的至少一种；
    3)制备凝胶：向上述稀土硅溶胶中加入凝胶催化剂，稀土硅溶胶转变为稀土掺杂凝胶，记为稀土-SiO 2凝胶；
    4)溶剂置换步骤：使用乙醇置换出稀土-SiO 2凝胶中的水、卤素离子及其他杂质；
    5)干燥：对上述稀土-SiO 2凝胶进行乙醇超临界干燥，得到稀土掺杂二氧化硅气凝胶。
  6. 根据权利要求5所述的制备方法，其特征在于，步骤1)的硅溶胶中，还可以加入硅微粉；
    和/或，步骤1)的硅溶胶中，还可以加入遮光剂。
  7. 根据权利要求5-6任一项所述的制备方法，其特征在于，步骤3)制备凝胶过程中还引入纤维，采用下述两种方式中的一种：
    第一种方式：向上述稀土硅溶胶中加入凝胶催化剂后，将其浇筑至纤维预制件中，之后静置获得凝胶；
    第二种方式：向上述稀土硅溶胶中加入凝胶催化剂后，再加入增强纤维以及纤维分散剂，之后静置获得凝胶。
  8. 根据权利要求5-7任一项所述的制备方法，其特征在于，步骤4)之前还包括一个改性步骤，具体包括：
    3’)改性：将上述稀土-SiO 2凝胶与改性剂混合，得到改性的稀土-SiO 2凝胶；
    4)溶剂置换：使用乙醇进行溶剂置换。
  9. 根据权利要求5或6所述的制备方法，其特征在于，所述方法中采用多种硅源与多种稀土化合物的组合。
  10. 根据权利要求7所述的制备方法，其特征在于，所述硅源选自硅酸钠、正硅酸乙酯、正硅酸甲酯、四丙氧基硅烷、四丁氧基硅烷、二甲基二甲氧基硅烷或二甲基二乙氧基硅烷中的至少一种。
  11. 根据权利要求7所述的制备方法，其特征在于，所述醇溶剂是甲醇、乙醇或其组合。
  12. 根据权利要求7所述的制备方法，其特征在于，第一次混合的时间为10min～15min。
  13. 根据权利要求7所述的制备方法，其特征在于，所述稀土金属硝酸盐为硝酸钇、硝酸钪、硝酸钕或其组合。
  14. 根据权利要求7所述的制备方法，其特征在于，所述遮光剂为二氧化钛、炭黑、SiC、六钛酸钾、ZrO 2或其组合。
  15. 根据权利要求7所述的制备方法，其特征在于，所述凝胶催化剂为自氨水、二甲基甲酰胺、氨水乙醇稀释液、碳酸氢铵、碳酸铵中的至少一种。
  16. 根据权利要求7所述的制备方法，其特征在于，所述硅微粉的添加量是1％-15％。
  17. 根据权利要求7所述的制备方法，其特征在于，步骤1)中还引入水解催化剂，所述水解催化剂为盐酸、草酸、硝酸、硫酸、磷酸或其组合。
  18. 根据权利要求17所述的制备方法，其特征在于，所述水解催化剂溶液的质量分数为0.05～0.1wt％。
  19. 根据权利要求18所述的制备方法，其特征在于，所述硅源与所述水解催化剂的摩尔比为1:(10～4)。
  20. 根据权利要求7所述的制备方法，其特征在于，所述纤维为水镁石纤维、陶瓷纤维、玻璃纤维、石英纤维、莫来石纤维中的至少一种。
  21. 根据权利要求20所述的制备方法，其特征在于，所述莫来石纤维是枝晶增强莫来石纤维。
  22. 根据权利要求5-9任一项所述的制备方法，其特征在于，步骤5)中，进行乙醇超临界干燥前，使用N 2预先充满反应釜，预充N 2的压力为1-4Mpa。
  23. 根据权利要求5-9任一项所述的制备方法，其特征在于，步骤5)中，乙醇超临界干燥的温度为240℃以上，保温2～4h至釜内压力为8～10Mpa后，缓慢释放釜内压力至常压。
  24. 一种二氧化硅气凝胶颗粒，其特征在于，所述颗粒具有核壳结构；其中，外壳是铝氧化物和/或铝盐而内核是权利要求1-4任一项所述的稀土掺杂二氧化硅气凝胶，或者，外壳是权利要求1-4任一项所述的稀土掺杂二氧化硅气凝胶而内核是铝氧化物和/或铝盐。
  25. 权利要求24所述二氧化硅气凝胶颗粒的制备方法，其特征在于，所述制备方法包括以下步骤：
    先制备所述稀土掺杂二氧化硅气凝胶的颗粒，然后与铝氧化物和/或铝盐混合，制备得到所述外壳是铝氧化物和/或铝盐而内核是上述的稀土掺杂二氧化硅气凝胶的颗粒；
    或者，采用权利要求5-9任一项所述的稀土掺杂二氧化碳气凝胶的制备方法制备所述气凝胶，其中在所述步骤3)的制备凝胶的过程中加入铝氧化物和/或铝盐颗粒，从而可以制备得到所述外壳是上述的稀土掺杂二氧化硅气凝胶而内核是铝氧化物和/或铝盐的颗粒。
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