CN108640643B - Process for manufacturing silicon dioxide aerogel containing reinforced fibers - Google Patents
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Abstract
A process for preparing silicon dioxide aerogel containing reinforced fibers adopts 3-amino trihydroxy silane, oxygen-free deionized water, halogenated silane and ammonia water as raw materials, wherein the ratio of 3-amino trihydroxy silane to halogenated silane to ammonia water is as follows: oxygen-free deionized water: halogenated silane: the ammonia water is used in a molar ratio of 1: 2.0-4.0: 0.3-3.0: 0.1-0.8; before preparing the silica hydrosol, adding a certain amount of reinforcing fibers, polymerizing the reinforcing fibers into the nano hydrosol by utilizing 3-amino trihydroxy silane under an alkaline condition, aging the hydrosol for a certain time, carrying out surface modification on the hydrosol to form gel, and drying the gel at different temperatures twice under normal pressure to prepare the silica aerogel containing the reinforcing fibers. The silica aerogel materials containing reinforcing fibers of the present invention can be used as space suits, climbing wear, diving suits, etc., in addition to being used as lithium sulfur battery electrolyte packs.
Description
Technical Field
The invention belongs to the synthesis of high polymer materials, and particularly relates to the field of application of heat resistance and heat preservation of required materials.
Background
Aerogel is a solid form, one of the world's less dense solids. The density was 3kg/m3. A common aerogel is a silica aerogel, which was first produced by Kistler, the american scientist, in 1931 because of gambling with her friends. There are many kinds of aerogels, including silicon-based, carbon-based, sulfur-based, metal oxide-based, metal-based, and the like. aerogel is a combination word where aeroo is an adjective, meaning flying, and gel is obviously a gel. Literally means a gel that can fly. Any gel can be called aerogel as long as it can be dried and the internal solvent is removed, and the shape of the gel can be basically kept unchanged, and the product has high porosity and low density.
It has a very low density, and the currently lightest silicone aerogels are only 0.16 milligrams per cubic centimeter, slightly less dense than air, and are also known as "frozen smoke" or "blue smoke". Because the particles inside are very small (on the order of nanometers), visible light is less scattered through it, just like sunlight through air. It therefore looks blue like the sky (if nothing else is doped inside) and somewhat red against the light. (sky is blue and evening sky is red). As the aerogel is generally more than 80 percent of air, the aerogel has very good heat insulation effect, and one inch of thick aerogel has the heat insulation function equivalent to that of 20 to 30 pieces of common glass. Even with the aerogel placed between the rose and the flame, the rose is not damaged at all. Aerogels have also found many uses in aerospace exploration, and such materials are useful in Russian "peace" space stations and in American "Mars pathfinder" detectors. Aerogels have also been used in particle physics experiments as detectors of the Cherotkoff effect. A particle discriminator, called Aerogel Cherenkov Counter (ACC), in the Belle test detector of the dielectric factory of the high-energy accelerator institute B, is a recent application example. The detector utilizes the low refractive index between liquid and gas of aerogel, and the high transmittance and solid state of aerogel, which is superior to the conventional method using low temperature liquid or high pressure air. At the same time, its lightweight properties are also one of the advantages.
Aerogels, the lightest solid in the world, have been recorded in the ginies world. The density of the new material is only 3.55kg/m3Only 2.75 times the density of air; dried pine Density (500 kg/m)3) 140 times it. This material looks like a solidified smoke, but its composition is similar to glass. Because of its extremely low density, it is very suitable for aerospace.
The new aerogel developed by Jones in the American aviation administration, which is mainly composed of silica and the like which purely contain reinforcing fibers, is used for propelling the laboratory by jet. In the manufacturing process, the liquid silicon compound is first mixed with a liquid solvent capable of rapid evaporation to form a gel, and then the gel is dried in an apparatus like a pressure cooker and subjected to heating and depressurization to form a porous sponge-like structure. The proportion of air in the aerogel finally obtained by jones was 99.8%.
Aerogels are sometimes referred to as "solid smoke" or "frozen smoke" because of their translucent color and ultra-light weight. The new material seems fragile and durable and can bear the high temperature of 1400 ℃. These properties of aerogels have many uses in aerospace exploration. Aerogel materials have been used in Russian "peace" number space stations and in American "Mars pathfinder" detectors.
The novel aerogel developed by the American national space navigation agency has the density of 3mg/cm3The book Jinis world record has been officially entered as "the lowest density solid in the world" at the present day.
This aerogel is translucent, pale blue and extremely lightweight, and is therefore also referred to as "solid smoke". The novel aerogel was developed by Stefin Jones, a jet propulsion laboratory materials scientist under the United states State aviation administration. Its main component is silica containing reinforcing fibers, like glass, but because 99.8% of it is air, the density is only one thousandth of that of glass.
Aerogels appear to be "weak against the wind" and are very robust in nature. It can bear pressure several thousand times of its own mass, and can be melted only when its temperature reaches 1200 deg.C. In addition, its thermal conductivity and refractive index are low, and its insulating ability is 39 times stronger than that of the best glass fiber. Due to these characteristics, aerogels are irreplaceable materials for aerospace exploration, and are used for thermal insulation in Russian and peace space stations and American Mars pathfinder detectors.
Aerogel has found far more than these applications in aerospace, and the united states national space agency "star dust" spacecraft is carrying it out a very important mission in space — the collection of comet particles. Scientists believe that comet particles contain the most primitive and oldest substances in the solar system, and research on them can help people to more clearly understand the history of the sun and planets. In 2006, a "star" airship returned the earth with the first comet-dust samples obtained by mankind.
However, collecting comet dust is not an easy task, its velocity is 6 times that of rifle bullets, although it is smaller than that of sand, but when it comes into contact with other substances at such high velocity, it may change its physical and chemical composition, even if it is completely vaporized. Today scientists have aerogels and the problem becomes simple. It acts like an extremely soft baseball glove and gently dampens the velocity of comet dust, stopping it slowly after sliding a distance equivalent to 200 times its length. Upon entering an "aerogel glove," the dust leaves behind a carrot-like track, which scientists can easily find with the aerogel because it is almost transparent.
Originally named by s.kistler, aerogel was defined as: the wet gel is subjected to supercritical drying to obtain a material called aerogel. In the middle and later 90 s, with the advent and development of atmospheric drying technology, the definition of aerogel generally accepted in the middle and later 90 s was: regardless of the drying method employed, the resulting material is referred to as an aerogel so long as the liquid in the wet gel is replaced by gas while the network structure of the gel remains substantially unchanged. The aerogel is structurally characterized by having a high-permeability cylindrical multi-branch nano porous three-dimensional network structure, having extremely high porosity, extremely low density, high specific surface area and ultrahigh pore volume rate, and having a bulk density of 0.003-0.500g/cm-3The range is adjustable. (the density of air is 0.00129g/cm-3)。
The preparation of aerogels generally consists of a sol-gel process and a supercritical drying treatment. In the sol-gel process, nanoclusters with different structures are formed in a solution by controlling hydrolysis and polycondensation reaction conditions of the solution, the clusters are adhered to each other to form a gel, and the periphery of a solid skeleton of the gel is filled with a liquid reagent remaining after chemical reaction. In order to prevent the damage of the material structure caused by the surface tension in the micro-pores in the drying process of the gel, a supercritical drying process is adopted for treatment, the gel is placed in a pressure container for heating and boosting, so that the liquid in the gel is changed into supercritical fluid, a gas-liquid interface disappears, the surface tension does not exist any more, and at the moment, the supercritical fluid is released from the pressure container, so that the low-density aerogel material with the porous, disordered and nano-scale continuous network structure can be obtained.
The aerogel contains a large amount of air, the typical pore linearity is in the range of l-l 00 nanometers, the pore rate is more than 80 percent, and the aerogel is a porous material with a nano structure and shows unique properties in the aspects of mechanics, acoustics, heat, optics and the like. The scattering of light and sound is much smaller than that of the traditional porous material, and the unique properties not only make the material interesting in basic research, but also hold a wide application prospect in many fields.
In fractal structure research. The silicon aerogel is used as a nano porous material with a controllable structure, the apparent density of the silicon aerogel obviously depends on the scale size, the density of the silicon aerogel usually has scale invariance in a certain scale range, namely, the density is reduced along with the increase of the scale, and the silicon aerogel has a self-similar structure. The correlation length can be changed within a range of two orders of magnitude by changing the preparation conditions of the aerogel. Therefore, silica aerogel has become the best material for studying fractal structure and its dynamic behavior.
The nano porous aerogel material has important application value, if a porous target material lower than critical density is utilized, the beam quality of X-ray laser generated by electron collision excitation can be expected to be improved, the driving energy is saved, the novel porous target of a micro-spherical node structure is utilized, the rapid cooling of three-dimensional adiabatic expansion of a plasma can be realized, the gain coefficient of the X-ray laser generated by an electron composite mechanism is improved, the ultralow-density material is utilized to adsorb nuclear fuel, and the high-gain freezing target of laser inertial confinement fusion can be formed. The aerogel has a fine nano porous network structure, a huge specific surface area and controllable structure mesoscale, and becomes an optimal candidate material for developing a novel low-density target.
The fine nano-network structure of the silica aerogel effectively limits the propagation of local thermal excitation, and the solid thermal conductivity of the silica aerogel is 2-3 orders of magnitude lower than that of a corresponding glassy material. The nanopores suppress the contribution of gas molecules to heat conduction. The refractive index of the silica aerogel is close to l, and the ratio of annihilation coefficients of the silica aerogel to infrared light and visible light reaches more than 100, so that the silica aerogel can effectively transmit sunlight and prevent infrared heat radiation of ambient temperature, becomes an ideal transparent heat-insulating material, and has been applied to the aspects of solar energy utilization and building energy conservation. The radiation heat conduction of the silicon aerogel can be further reduced by means of doping, the heat conductivity of the carbon-doped aerogel at normal temperature and normal pressure can be as low as 0.013 w/m.K, the silicon-doped aerogel is a solid material with the lowest heat conductivity at present, and the silicon-doped aerogel is expected to replace polyurethane foam to become a novel refrigerator heat insulation material. The silicon aerogel can become a novel high-temperature heat-insulating material by doping titanium dioxide, the heat conductivity at 800K is only 0.03 w/m.K, and the silicon aerogel can be further developed as a new material matched with military products.
Silicon aerogel is also an ideal acoustic delay or high temperature sound barrier material due to its low acoustic velocity properties. The acoustic impedance of the material is wide in variable range (103-107 kg/m)2S) is an ideal acoustic resistance coupling material for an ultrasonic detector, such as a common acoustic resistance coil Zp of 1.5 × l07kg/m2S piezoelectric ceramics as ultrasonic generator and detector, and the acoustic resistance of air is only 400kg/m2S. The silicon aerogel with the thickness of l/4 wavelength is used as the acoustic resistance coupling material of the piezoelectric ceramic and the air, so that the transmission efficiency of sound waves can be improved, and the signal-to-noise ratio in the application of devices can be reduced. The preliminary experiment result shows that the density is 300kg/m3The left and right silicon aerogels are used as coupling materials, so that the sound intensity can be improved by 30dB, and if the silicon aerogels with density gradient are adopted, higher sound intensity gain can be expected.
In the aspects of environmental protection and chemical industry. The nano-structured aerogel can also be used as a novel gas filter, and is different from other materials in that the material has uniform pore size distribution and high porosity, thereby being a high-efficiency gas filter material. The aerogel has wide application prospect as a novel catalyst or a carrier of the catalyst.
The conductive porous material of carbon aerogel obtained after the organic aerogel is treated by a sintering process is a novel carbon material developed after fibrous activated carbon, and has a large specific surface area (60)0～1000m2Kg) and high conductivity (10-25 s/cm), and wide density variation range (0.05-1.0 g/cm)3) If the micro-hole is filled with proper electrolyte, a novel rechargeable battery can be made, which has the excellent characteristics of large storage capacity, small internal resistance, light weight, strong charge-discharge capacity, repeated use and the like, and the preliminary experiment result shows that: the charge capacity of the carbon aerogel reaches 3 x 104/kg2The power density was 7kw/kg, and the repeated charging and discharging performance was good.
As quantum dot structures are formed in the nano-network of the silicon aerogel, the results of Si doping by a chemical vapor infiltration method and C60 doping by a solution method show that the dopant exists in the form of nano-grains, and strong visible light emission is observed, so that strong evidence is provided for quantum confinement effect luminescence of the porous silicon. By utilizing the structure of the silica aerogel and the nonlinear optical effect of C60, novel laser protective glasses can be further developed. The method by doping is also an effective means of forming nanocomposite phase materials.
In addition, the silicon aerogel is a material with adjustable refractive index, and the mass and the energy of the high-energy particles can be determined by using aerogel media with different densities as Cherenkov threshold detectors. Because the high-speed particles easily penetrate into the porous material and gradually decelerate, the soft landing is realized, for example, the transparent aerogel is selected to capture the high-speed particles in the space, and the blocked and captured particles can be observed by naked eyes or a microscope.
As a novel nanoporous material, in addition to silica aerogel, other unit, binary or multi-element oxide aerogels, organic aerogels and carbon aerogels have been developed. As a unique material preparation means, the related process is widely applied to the development of other new materials, such as the preparation of porous silicon with extremely high porosity, the preparation of metal-aerogel mixed materials of high-performance catalysts, high-temperature superconducting materials, ultrafine ceramic powder and the like.
Ballistic resistance is the second important use of the novel aerogels. This company of the united states space agency is testing dwellings and military vehicles constructed with aerogel. According to the laboratory test, if a layer of aerogel with a thickness of about 6mm is applied to the metal sheet, no damage is caused to the metal sheet even in the direct explosion of explosives.
Environmental protection is the third important role of the novel aerogel. Scientists refer to aerogels as "super sponges" in their familiarity, which are highly desirable materials for adsorbing contaminants in water because of the hundreds of thousands of pores in the surface. The aerogel newly invented by american scientists can naturally suck out lead and mercury in water. According to the scientist, the aerogel is a perfect material for treating ecological disasters, for example, after a 1996 'sea express' tanker is submerged, 72000 tons of crude oil are leaked out, and if the aerogel is used, the aerogel cannot cause serious pollution to the whole coast.
The new aerogels will also step into our everyone's future daily life. For example, Dunlop sports equipment in the United states has successfully developed tennis rackets with aerogels. Such tennis rackets are said to have a greater ability to hit the ball; in the beginning of 2012, 66 years old bob stokes became the first english-based person to use aerogels for housing: the heat preservation and heating effect is very good, i reduce the temperature of the air conditioner by 5 ℃, and consequently, the indoor temperature is still very comfortable. "Mountaineers also fill hopes with the use of aerogels. The shoes worn by the UK mountaineering Enani Palment 2011 when climbing peaked are made of partial aerogel materials, and a sleeping bag of the UK mountaineering mountain Annier Palment also has a layer of the novel material.
The basic principle of aerogel preparation is to remove the solvent from the gel, leaving it with an intact framework. In the past case of aerogel production, scientists have mainly used sol-gel and template-directed methods. The former can be synthesized in batch, but has poor controllability; the latter can produce ordered structures, but depending on the fine structure and size of the template, are difficult to prepare in large quantities.
A new method is developed for a high-class subject group, and a template-free freeze drying method is explored: the aqueous solution in which the graphene and the carbon nano tube are dissolved is lyophilized at low temperature, so that the carbon sponge is obtained, the shape can be adjusted at will, the production process is more convenient, and the large-scale manufacture and application of the ultralight material are possible.
It is described that "carbon sponge" has high elasticity and can be restored to its original shape after being compressed by 80%. It has super-fast and super-high adsorption force to organic solvent, and is the highest oil-absorbing material reported so far. The existing oil absorption product can only absorb liquid with the mass about 10 times of the self mass, while the absorption capacity of the carbon sponge is about 250 times and can reach 900 times at most, and only absorbs oil but does not absorb water. The 'Daweiwang' takes organic substances very fast: each gram of such "carbon sponge" can absorb 68.8 grams of organic matter per second. In the 20 th century, laboratories are conducting further application studies on the adsorptive properties of this material. Researchers claim that the carbon sponge can also become an ideal phase change energy storage heat insulation material, a catalytic carrier, a sound absorption material and an efficient composite material. However, the application field and the prospect of the new material are difficult to accurately predict, and the new material can be moved out of a laboratory by depending on the imagination of the society and the industry, so that the application value is realized.
While high performance silica with reinforcing fibers has thermal stability at high temperature, and has flame retardant, insulating, radiation resistant and good mechanical properties. To explore new applications of the material, researchers in various countries are continuously seeking.
In Chinese patent No. ZL98811584.0, an aerogel process for improving the branching degree of organic silicon by adding silicon tetrachloride is introduced, wherein hydrogel is prepared firstly, and Si (OH) is formed in the hydrolysis process4The monomer is used for preparing the aerogel by the traditional process of preparing the aerogel from the hydrogel, so that the aerogel with a-SiO-network structure is formed, and the toughness of the aerogel prepared from silicon tetrachloride is relatively poor due to the fact that the molecular structure of the aerogel does not contain other flexible molecular chains.
Therefore, the high-performance aerogel material with excellent heat insulation and preservation performance is manufactured, and can be used as an aerospace suit, a climbing suit, a diving suit and the like besides being used for filling lithium-sulfur battery electrolyte, and can also be used in the fields of aerospace, petrochemical industry and automobile traffic, so that the application under relatively harsh environmental conditions can be met, the requirement that astronauts endure ultralow temperature during space walking can be met, the requirement that the divers and the mountaineers keep warm at low temperature in deep sea and high altitude can be met, the physical consumption and filling degree of the astronauts, the divers and the mountaineers under severe environmental conditions can be reduced, and the life safety of the astronauts, the divers and the mountaineers can be ensured.
The invention overcomes the defects of the prior preparation process of the silicon dioxide aerogel containing the reinforced fiber, namely, the tetraethyl orthosilicate hydrolysis process procedure exists in the preparation process, and aims to prepare silane containing polyhydroxy; in order to reduce the cost of the silicon dioxide aerogel containing the reinforced fibers, the invention directly applies trihydroxy silane containing amino, aims to improve the manufacturing speed of hydrosol, and reduces the hydrolysis process of silane in the prior art, thereby shortening the manufacturing time of the silicon dioxide aerogel containing the reinforced fibers.
Disclosure of Invention
The invention aims to research a manufacturing process of silica aerogel containing reinforced fibers, and the microstructure of the aerogel is improved by reasonably selecting process control conditions, raw materials and auxiliary materials on the premise of not increasing the production cost of the aerogel, so that the aim of optimizing the heat insulation performance of the aerogel is fulfilled.
The purpose of the invention is realized by the following means:
a process for preparing silicon dioxide aerogel containing reinforced fibers adopts 3-amino trihydroxy silane, oxygen-free deionized water, halogenated silane and ammonia water as raw materials, wherein the ratio of 3-amino trihydroxy silane to halogenated silane to ammonia water is as follows: oxygen-free deionized water: halogenated silane: the ammonia water is used in a molar ratio of 1: 3.0-5.0: 0.3-3.0: 0.1-0.8; the mass ratio of the reinforcing fibers to the silicon dioxide aerogel is 6-8: 94-92; before preparing silica hydrosol, adding a certain amount of reinforcing fiber, polymerizing 3-amino trihydroxy silane to form nano hydrosol under an alkaline condition, aging the hydrosol for a certain time, carrying out surface modification on the hydrosol to form gel, and drying the gel at two different temperatures under normal pressure to prepare the silica aerogel containing the reinforcing fiber, wherein the preparation process of the aerogel comprises the following steps:
1) dissolving 3-amino trihydroxysilane in oxygen-free deionized water, vigorously stirring for 3-8 min to completely dissolve the 3-amino trihydroxysilane, adding aramid 1313 fiber and aramid 1414 fiber with the diameters of 1-3 mu m and 3-6 mm, T300 type carbon fiber, ceramic fiber, silicon carbide fiber, aramid 1313 fibrid, aramid 1414 fibrid and PAN fibrid with the diameters of 6-8 mu m and 1-3 mm, stirring for 33-48 min, then dropwise adding 0.03-0.08 mol/L ammonia water solution into the solution, vigorously oscillating for 6-8 min, and stopping oscillating when the pH value of the solution is adjusted to 7 to prepare nano sol;
2) standing the nano sol obtained in the step 1) for 18-24 hours at room temperature to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; due to the fact that the isopropanol solution has high surface tension, after aging, the sample is immersed in the n-hexane solution for 3-6 hours, and then the isopropanol solution in the gel can be replaced. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the displaced sample is immersed in a solvent with the molar ratio of 6-9: 1-4: 1-2 of n-hexane-trimethylchlorosilane and silicon tetrachloride solution, and carrying out surface modification at the temperature of 40-60 ℃ for 18-36 hours.
3) And (3) placing the gel sample obtained in the step (2) in a drying oven at the temperature of 60-80 ℃, drying for 2-3 h, then raising the temperature of the drying oven to 80-120 ℃, and drying for 6-8 h to obtain the silica aerogel containing the reinforced fibers.
The preparation process of the silica aerogel containing the reinforced fibers adopts 3-amino trihydroxy silane as an hydrosol monomer, aims to reduce the hydrolysis process procedure of alkyl silane, simultaneously fully utilizes the chemical activity of hydroxyl and amino, enables the preparation of the silica hydrosol containing the reinforced fibers to be easy, enables the molecular weight of the silica hydrosol containing the reinforced fibers to be higher than that of tetraethyl orthosilicate hydrolysis polycondensation products under relatively low conditions, adds proper amount of silicon tetrachloride with higher branching degree in the surface modification process of gel in order to improve the loose and porous porosity of the aerogel, enables the holes of the silica aerogel containing the reinforced fibers to be more uniformly distributed due to the fact that the silicon tetrachloride is in a symmetrical right triangle body, and accordingly improves the heat preservation and heat insulation performance of the silica aerogel containing the reinforced fibers, thereby widening the application field of the silica aerogel containing reinforcing fibers of the present invention.
The process flow introduction of the invention is as follows:
a process for preparing silicon dioxide aerogel containing reinforced fibers comprises the steps of adopting 3-amino trihydroxysilane, oxygen-free deionized water, halogenated silane and ammonia water as raw materials, adding a certain amount of reinforced fibers before preparing silicon dioxide hydrosol, polymerizing the 3-amino trihydroxysilane into nano hydrosol under an alkaline condition, carrying out surface modification on the hydrosol after the hydrosol is aged for a certain time to form gel, and drying the gel at different temperatures twice under normal pressure to prepare the silicon dioxide aerogel containing the reinforced fibers.
The invention has the beneficial effects that:
the silica aerogel material containing the reinforced fibers can be used as an aerospace suit, a climbing suit, a diving suit and the like besides being used for filling lithium-sulfur battery electrolyte, can also be used in the fields of aerospace, petrochemical industry and automobile traffic, can meet the requirements of astronauts on tolerating ultralow temperature during space walking, can meet the requirements of the divers and the climbers on low-temperature heat preservation in deep sea and high altitude, and can reduce the physical consumption degree of the astronauts, the divers and the climbers under severe environmental conditions so as to ensure the life safety of the astronauts, the climbing suit and the like.
Detailed Description
The process of the present invention is further described in detail below with reference to examples.
Example 1:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia water is 1:3.0:0.3: 0.1; the mass ratio of the reinforcing fibers to the silica aerogel is 6: 94. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 8min to completely dissolve, adding aramid 1313 fiber with diameter of 1 μm and length of 3mm, stirring for 48min, dropwise adding 0.03mol/L ammonia water solution into the solution, vigorously oscillating for 6min, and stopping oscillation when pH value of the solution is adjusted to 7 to obtain nano sol.
Standing the obtained nano sol for 24 hours at room temperature to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 6 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the displaced sample is immersed in a solvent with the molar ratio of 9: 1: 1, carrying out surface modification in n-hexane-trimethylchlorosilane and silicon tetrachloride solution at the modification temperature of 60 ℃ for 18 hours; and (3) putting the obtained gel sample into an oven at 80 ℃ for drying for 2h, raising the temperature of the oven to 120 ℃, and drying for 6h to obtain the silica aerogel containing the reinforced fibers.
Example 2:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia water is 1:5.0:3.0: 0.8; the mass ratio of the reinforcing fibers to the silica aerogel is 8: 92. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 3min to completely dissolve the 3-amino trihydroxy silane, adding aramid 1414 fibers with the diameter of 3 microns and the length of 6mm, stirring for 48min, then dropwise adding 0.08mol/L ammonia water solution into the solution, vigorously oscillating for 6-8 min, and stopping oscillating when the pH value of the solution is adjusted to 7 to obtain the nano sol.
Standing the obtained nano sol at room temperature for 18h to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 3 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the displaced sample is immersed in a solvent with the molar ratio of 6: 4: 2, carrying out surface modification in n-hexane-trimethylchlorosilane and silicon tetrachloride solution at the modification temperature of 40 ℃ for 36 hours; and (3) putting the obtained gel sample into a 60 ℃ oven, drying for 3h, raising the temperature of the oven to 80 ℃, and drying for 8h to obtain the silica aerogel containing the reinforced fibers.
Example 3:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia to ammonia is 1:3.6:0.4: 0.2; the mass ratio of the reinforcing fibers to the silica aerogel is 6.3: 93.7. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 5min to completely dissolve, adding T300 type carbon fiber with diameter of 6 μm and length of 3mm, stirring for 36min, dropwise adding 0.04mol/L ammonia water solution into the solution, vigorously oscillating for 6.3min, and stopping oscillation when pH value of the solution is adjusted to 7 to obtain nano sol.
Standing the obtained nano sol at room temperature for 19h to age the sol; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 3.5 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the replaced sample is immersed in a solvent with the molar ratio of 7.2: 2.8: 1.3, carrying out surface modification in a normal hexane-trimethylchlorosilane and silicon tetrachloride solution, wherein the modification temperature is 44 ℃ and the modification time is 26 hours; and (3) putting the obtained gel sample into an oven at 71 ℃ for drying for 2.3h, raising the temperature of the oven to 101 ℃, and drying for 7.4h to obtain the silica aerogel containing the reinforced fibers.
Example 4:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia to ammonia is 1:3.8:1.6: 0.4; the mass ratio of the reinforcing fibers to the silica aerogel is 7.1: 92.9. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 6min to completely dissolve, adding ceramic fiber with the length of 1mm and the diameter of 8 μm, stirring for 38min, dropwise adding 0.06mol/L ammonia water solution into the solution, vigorously oscillating for 7min, and stopping oscillation when the pH value of the solution is adjusted to 7 to obtain the nano sol.
Standing the obtained nano sol at room temperature for 21h to age the sol; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 5 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the replaced sample is immersed in a solution prepared by mixing the following components in a molar ratio of 8.1: 1.9: 1.6 of normal hexane-trimethylchlorosilane and silicon tetrachloride solution, wherein the modification temperature is 51 ℃, and the modification time is 31 h; and (3) putting the obtained gel sample into an oven at 73 ℃ for drying for 3h, then raising the temperature of the oven to 111 ℃, and drying for 7h to obtain the silica aerogel containing the reinforced fibers.
Example 5:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia to ammonia is 1:4.6:2.6: 0.6; the mass ratio of the reinforcing fibers to the silica aerogel is 7.6: 92.4. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 6.8min to completely dissolve, optionally adding silicon carbide fiber with diameter of 6 μm and length of 1mm, stirring for 41min, dropwise adding 0.05mol/L ammonia water solution into the solution, vigorously oscillating for 8min, and stopping oscillation when pH value of the solution is adjusted to 7 to obtain nano sol.
Standing the obtained nano sol for 22h at room temperature to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 5.6 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the replaced sample is immersed in a solution prepared by mixing the following components in a molar ratio of 8.4: 1.6: 1.8, carrying out surface modification in a solution of n-hexane-trimethylchlorosilane and silicon tetrachloride at the modification temperature of 58 ℃ for 26 hours; and (3) putting the obtained gel sample into a 68 ℃ oven, drying for 3h, raising the temperature of the oven to 118 ℃, and drying for 7.4h to obtain the silica aerogel containing the reinforced fibers.
Example 6:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia to ammonia is 1:4.4:1.9: 0.4; the mass ratio of the reinforcing fibers to the silica aerogel is 6.8: 93.2. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 6min to completely dissolve, optionally adding aramid fiber 1313 for precipitating fiber, stirring for 33min, dropwise adding 0.03mol/L ammonia water solution into the solution, vigorously oscillating for 8min, and stopping oscillation when the pH value of the solution is adjusted to 7 to obtain the nano sol.
Standing the obtained nano sol for 24 hours at room temperature to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 6 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the displaced sample is immersed in a solvent with the molar ratio of 9: 1:2, carrying out surface modification in n-hexane-trimethylchlorosilane and silicon tetrachloride solution at the modification temperature of 60 ℃ for 18 hours; and (3) immediately putting the obtained gel sample into an oven at 80 ℃, drying for 3h, then keeping the temperature of the oven at 80 ℃, and drying for 8h to obtain the silica aerogel containing the reinforced fibers.
Example 7:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia to water is 1:3.8:2.8: 0.6; the mass ratio of the reinforcing fibers to the silica aerogel is 8: 92. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 3min to completely dissolve, adding aramid fiber 1414 for precipitating fiber, stirring for 38min, dropwise adding 0.03mol/L ammonia water solution into the solution, vigorously oscillating for 8min, and stopping oscillation when the pH value of the solution is adjusted to 7 to obtain the nano sol.
Standing the obtained nano sol for 24 hours at room temperature to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; due to the fact that the isopropanol solution has high surface tension, after aging, the sample is immersed in the n-hexane solution for 3-6 hours, and then the isopropanol solution in the gel can be replaced. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the displaced sample is immersed in a solvent with the molar ratio of 6: 4: 2, carrying out surface modification in n-hexane-trimethylchlorosilane and silicon tetrachloride solution at the modification temperature of 50 ℃ for 33 h; and (3) putting the obtained gel sample into an oven at 80 ℃ for drying for 3h, raising the temperature of the oven to 120 ℃, and drying for 8h to obtain the silica aerogel containing the reinforced fibers.
Example 8:
the process formula comprises the following steps:
with 3-aminotrihydroxysilane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia to ammonia is 1:4.8:2.1: 0.4; the mass ratio of the reinforcing fibers to the silica aerogel is 7: 93. the manufacturing process of the aerogel comprises the following steps:
dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 6min to completely dissolve, adding PAN fibrid, stirring for 46min, dropwise adding 0.06mol/L ammonia water solution into the solution, vigorously oscillating for 6min, and stopping oscillation when the pH value of the solution is adjusted to 7 to obtain the nano sol.
Standing the obtained nano sol at room temperature for 23h to age the sol; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the isopropanol solution in the gel can be replaced by immersing the sample in the n-hexane solution for 5 hours after aging. In order to reduce the surface energy of the gel three-dimensional structure in the later drying process, the replaced sample is immersed in a solution prepared by mixing the following components in a molar ratio of 8.5: 1.5: 1.5, carrying out surface modification in a solution of n-hexane-trimethylchlorosilane and silicon tetrachloride, wherein the modification temperature is 56 ℃, and the modification time is 34 hours; and (3) putting the obtained gel sample into a 76 ℃ oven, drying for 2.6h, raising the temperature of the oven to 116 ℃, and drying for 7.6h to obtain the silica aerogel containing the reinforced fibers.
Claims (2)
1. The preparation process of the silica aerogel containing the reinforced fibers is characterized in that the aerogel adopts 3-amino trihydroxy silane, oxygen-free deionized water, halogenated silane and ammonia water as raw materials, wherein the content of the 3-amino trihydroxy silane: oxygen-free deionized water: halogenated silane: the molar ratio of ammonia water is 1.0: 3.0-5.0: 0.3-3.0: 0.1-0.8; the mass ratio of the reinforcing fibers to the silicon dioxide aerogel is 6-8: 94-92, wherein the reinforced fiber is aramid 1313 fiber, aramid 1414 fiber, or carbon fiber with the diameter of 1-3 μm and the length of 3-6 mm, the aramid fiber is aramid 300 type carbon fiber with the diameter of 6-8 μm and the length of 1-3 mmT, ceramic fiber, silicon carbide fiber, aramid 1313 fibrid, aramid 1414 fibrid and PAN fibrid; when preparing the nano hydrosol, adding a certain amount of reinforcing fibers, stirring for a certain time, polymerizing the 3-amino trihydroxy silane into the nano hydrosol under an alkaline condition, aging the hydrosol for a certain time, carrying out surface modification on the hydrosol to form gel, drying the gel at two different temperatures under normal pressure to prepare the silica aerogel containing the reinforcing fibers, wherein the preparation process of the aerogel comprises the following steps:
1) dissolving 3-amino trihydroxy silane in oxygen-free deionized water, vigorously stirring for 3-8 min to completely dissolve the 3-amino trihydroxy silane, adding reinforcing fibers, stirring for 33-48 min, then dropwise adding 0.03-0.08 mol/L ammonia water solution into the solution, vigorously oscillating for 6-8 min, and stopping oscillating when the pH value of the solution is adjusted to 7 to prepare nano hydrosol;
2) standing the nano hydrosol obtained in the step 1) at room temperature for 18-24 h to age the gel; in order to prevent the solvent volatilization of the sample in the gel aging process, a layer of isopropanol is required to cover the surface of the gel; because the isopropanol solution has higher surface tension, the sample is immersed in the n-hexane solution for 3-6 hours after aging, and then the isopropanol solution in the gel can be replaced, so that the surface energy of the three-dimensional structure of the gel in the later drying process is reduced, and the replaced sample is immersed in the mixed solution with the molar ratio of 6-9: 1-4: 1-2 of n-hexane, trimethylchlorosilane and silicon tetrachloride solution, and carrying out surface modification at the temperature of 40-60 ℃ for 18-36 h;
3) and (3) placing the gel sample obtained in the step 2) in a drying oven at the temperature of 60-80 ℃, drying for 2-3 hours, then raising the temperature of the drying oven to 80-120 ℃, and drying for 6-8 hours to obtain the silica aerogel containing the reinforced fibers.
2. The process for preparing silica aerogel containing reinforcing fibers according to claim 1, wherein the halosilane is trimethylchlorosilane or silicon tetrachloride.
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