What Aerogels are?
Airgel, also known as dry gel. When the gel off most of the solvent, the gel content is much less than in the liquid content of the solids, or gel spatial network structure is filled with a gas medium, the look as a solid, which is the xerogel, but also called airgel. Such as gelatin, gum arabic, silica gel, hair, nails and so on. Airgel also has properties of the gel, i.e., having a swelling action, a thixotropic effect, syneresis. Chinese name: English name of airgel: aerogel English name: aerogel Nickname: Dry Gel Form: solid physical form of development time: 1931 Owner: Kistler article update:? Aerogels in the end is what material
airgel material is a solid form, the world\’s smallest density of the solid. Density of 3 kilograms per cubic meter. General common silicon airgel airgel, which was first proposed by American scientists Kistler bet made in 1931 because of their friends. Many types of airgel, silicon-based, carbon-based, sulfur-based, metal oxide, metal-based and the like. aerogel is a combination of words, here aero is an adjective, represents flight, gel apparently gel. Literally can fly gel. It can be any substance as long as the gel after drying after removal of the solvent inside, but also to substantially maintain its shape unchanged, and the product having a high porosity, low density, can call all the airgel. Because the low density airgel lightest only 0.16 milligrams per cubic centimeter, slightly lower than the density of air, it is also called \”frozen smoke\” or \”blue smoke.\” Since the inside of the particles are very small (nanometer scale), so when it is visible through a small scattering (Rayleigh scattering), just as the sun through the air. So, it looked like the sky and the blue (if there is no doping other things), if we look to the light a little red. (The sky is blue, and the evening sky is red). Since the airgel is generally more than 80% of air, so there is very good thermal insulation effect, quite inch thick airgel 20-30 ordinary glass. Even on the airgel between Rose and flame, the Rose will remain intact. Aerogels in space exploration is also a variety of purposes, in the Russian \”Peace\” space station and the United States \”Mars Pathfinder\” probe has used this material. Also airgel particle physics experiments, as Cherenkov effectDetector. Bit Belle experiment detector KEK B meson in the factory called airgel Cherenkov counter (Aerogel Cherenkov Counter, ACC) particle discriminator, it is a new application instance. Low refraction index between liquid and gas characteristics of the detectors utilized airgel, as well as the nature of the solid and high transmittance, is superior to the traditional practice of using high pressure air or cryogenic liquids. Meanwhile, the nature of which is the advantage of lightweight one.
airgel, the world\’s lightest solid, has been selected for the Guinness Book of World Records. This new material density of only 3.55 kg per cubic meter, is only 2.75 times the density of air; dried pine density (500 kg per cubic meter) it is 140 times. This solidified material looks like smoke, but its composition is similar to the glass. Because of its density is extremely small, is very suitable for aerospace. NASA\’s Jet Propulsion Laboratory, the Laboratory Dr. Jones developed a new type of airgel, is mainly composed of pure silica and other components. In the production process, the liquid silicon compound is first mixed with a liquid solvent can evaporate quickly, form a gel, then the gel placed in a similar pressure cooker instrument dried, and heated and down, forming a porous sponge like structure. Aerogels in air proportion Dr. Jones eventually accounted for 99.8%. Airgel its translucent color and ultra-light weight, sometimes referred to as \”solid smoke\” or \”frozen smoke.\” This new material seems fragile, in fact, very durable, can withstand up to 1400 degrees Celsius temperature. These properties of aerogels have many uses in space exploration. Russian \”Peace\” space station and the United States \”Mars Pathfinder\” on the detector, have used the airgel material. NASA developed a new type of airgel, due to the density of only 3 milligrams per cubic centimeter, recently it has emerged as \”the world\’s lowest density solid\” officially appeared in the \”Guinness Book of World Records.\” Such airgel translucent light blue, very light weight, so it is also called it \”solid smoke.\” The new airgel is a subsidiary of NASA \’\’s Jet Propulsion Laboratory \”Materials scientist Dr. Steven Jones developed. Its main component is silica and glass-like, but because it is 99.8% air, denseOnly one-thousandth of the glass. Airgel seemingly \”fragile\”, in fact, very durable. It can withstand thousands of times corresponding to the pressure of its own mass, not melt until the temperature reaches 1200 degrees Celsius. In addition to its low thermal conductivity and the refractive index, but also the insulating capacity of 39 times stronger than the best glass fibers. Due to possess these characteristics, airgel space exploration has become irreplaceable material, the Russian \”Peace\” space station and the United States \”Mars Pathfinder\” probe will use it for thermal insulation. Airgel applications in aerospace is much more than that, NASA\’s \”Stardust\” spacecraft is with it performs a very important mission in space — collect comet particles. Scientists believe that comets contain particles in the solar system\’s most primitive and oldest material, study it can help people more clearly understand the history of the sun and planets. In 2006, the \”Stardust\” spacecraft will carry the first batch comet Stardust sample obtained from a human return to Earth. Comet dust collection but not an easy task, its velocity rifle bullets corresponds to 6 times, although the volume is smaller than grains of sand, but at such a high speed when it is in contact with other substances, their physical and chemical composition of both It may change, or even completely evaporated. Now scientists with airgel, the problem becomes very simple. It is like a very soft baseball glove, gently abatement can speed comet dust, making it glide to slow down after a period equivalent to the length distance itself 200 times. After entering the \”airgel gloves\”, Stardust will leave period carrot shaped trajectory, because the airgel is almost transparent, scientists can easily find these particles in accordance with the track.
The method of preparing aerogels
airgel was originally named by S.Kistler, because he supercritical drying method successfully silica airgel, airgel it is defined as: wet gel by supercritical drying of the resulting material, called airgel. In the late 1990s, with the emergence and development of normal pressure drying technology, the definition generally accepted in the late 1990s airgel is: regardless of the drying method employed, as long as the liquid in the wet gel is gas substituent, while the gel network structure basically remain unchanged, so the resulting material is called airgel. Characterized in that airgel structures with high permeability cylindrical multi-branched nano-porous three network structure, with a high aperture ratio, low density, high specific surfaceArea, high pore volume fraction of a bulk density in the range 0.003-0.500 g / cm-3 is adjustable. (Air density is 0.00129 g / cm-3). Airgel is typically composed of a sol-gel process and the supercritical drying process. In the sol-gel process through controlled hydrolysis and polycondensation conditions of the solution, forming a nanocluster different structures in vivo in a solvent, mutual adhesion between the clusters formed gel, and the gel around the solid skeleton is after the full chemical reaction remaining liquid reagent. In order to prevent the surface tension of the gel during drying lead to destruction of the material of the microporous structure of the hole, the supercritical drying process, the gel was placed in a pressure vessel heated boosted liquid phase change occurs within the gel supercritical fluid, the gas-liquid interface disappears, the surface tension no longer exist, then the release of such supercritical fluid from the pressure vessel, to obtain a porous, disorder, low-density gas having a continuous network structure of the order of nanometers gel material.
in terms of Fractal Structure. Aerosilicon controllable as a configuration nanoporous material that exhibits clearly dependent on the density scale size, within a certain size range, which often have a density scale invariance, i.e., increasing the density decreases with the scale, and self-similar structure, structural dynamics fractal structure in terms of aerogels also indicate, in different scales, the dispersion relation of three distinct excitation region, respectively corresponding to phonon excitation fracton and particle mode. Airgel change preparation conditions, it may be associated with length variation in the range of two orders of magnitude. Thus a great material aerosilicon Fractal Structure and kinetic behavior.
1, in the \”863\” high-tech research in high power laser
nanoporous material has important applications, such as the use of a porous target material below the critical density, it is expected to improve the electron impact excitation beam generated by X-ray laser quality, save driving energy, the use of new porous microspheroidal target node structure, rapid cooling can be realized like the three-dimensional adiabatic expansion from the body, to increase the gain factor of the x-ray laser produced electron recombination mechanism, using ultra low density fuel adsorption material, constitutes the high gain can be frozen in inertial confinement fusion targets. Nanoporous airgel thin network structure, huge surface area, controllable dimensionally mesoscopic structures, the best candidate for the development of new target density.
2, a heat insulating material in the
silicon airgel thin nano network structure effectively limits the spread of excitation of localized hot, solid state thermal conductivity lower than the corresponding glassy material is 2-3 orders of magnitude . Nano microvoids inhibit heat transfer to the gas molecules contribute. Aerosilicon refractive index close to L, and the ratio coefficient annihilation infrared and visible light up to 100 or more, infrared radiation can be transmitted efficiently sunlight and prevent the ambient temperature, an ideal transparent insulation materials in the use of solar energy and building energy efficiency has been applied. By means of doping, can further reduce radiant heat conduction of silicon airgel, carbon airgel mixed at normal temperature and pressure can be as low thermal conductivity 0.013w / m · K, the thermal conductivity of the lowest solid material, It is expected to become a new refrigerator alternative to polyurethane foam insulation materials. Incorporation of titanium dioxide can be aerosilicon new high temperature insulation material, the thermal conductivity at 800K rate of 0.03w / m · K, as a military supporting new materials will be further developed. Since the low sound velocity characteristics of silicon aerogels, it is an ideal acoustic delay or high temperature insulation materials. Large acoustic impedance variable range of the material (103-107 kg / m2 · s), is an ideal ultrasound probe is coupled acoustically resistive material, such as a conventional sound barrier turns Zp = 1.5 × l07 kg / m2 · s as a piezoelectric ceramic ultrasonic wave generator and the detector, and the sound of the air resistance is only 400 kg / m2 · s. Having a thickness of l / 4 wavelength as the sound aerosilicon piezoelectric ceramic material and the air barrier coupling. Can improve the transmission efficiency of the acoustic wave, reducing the signal to noise ratio in device applications. Preliminary results show that the silicon density of about / m3 300 kg airgel as a coupling material can improve the sound intensity 30 dB, if the silicon airgel has a density gradient, is expected to be higher sound intensity gain. In environmental protection and chemical industry. Aerogels may also be used as novel nanostructures gas filter, is different from other materials with a uniform distribution of the material pore size, high porosity, the material is a highly efficient gas filter. Since the material is extremely large specific surface and volume. Aerogels in the carrier side as a new catalyst or catalysts and also has broad application prospects.
3, in terms of the energy storage device
Organic aerogels obtained after treatment after sintering process of this electrically conductive porous carbon airgel Following the activated carbon fiber material is developedA novel carbon material, which has a large surface area (600-1000 m2 / g) and high electrical conductivity (10-25 s / cm). Moreover, a wide range of density (0.05-1.0 g / cm3). As cave micropores charged into a suitable electrolyte may be made of new rechargeable battery having a large storage capacitance, internal resistance, light weight, high charge-discharge capacity, can be repeatedly used and other outstanding features, preliminary results show that: the charge capacity of the carbon airgel 3 × 104 / kg2, power density of 7 kw / kg, repeated charge and discharge performance good. In the study of quantum size effect material. Since the quantum dot structure is formed within the silicon airgel nano network, a chemical vapor infiltration doped Si doped results indicate that the C60 and the solution process, the dopant is present in the form of nanocrystalline grains, and observed a strong visible emission, It provides strong evidence for the emission quantum confinement effect of porous silicon. Silicon airgel structure and the nonlinear optical effects of C60, can be further developed new laser goggles. Effective means of phase nano-composite material is formed by a method of doping. Further, the refractive index of silicon aerogels are adjustable material used as a medium of different density airgel Cerenkov threshold detector may determine the mass and energy of energetic particles. Due to high-velocity particles easily penetrate the porous material and gradually decelerated, \”soft landing\”, such as the selection of high-speed capture transparent airgel particles in the space, with the naked eye or microscope is blocked, the captured particles. As a new nanoporous materials, aerogels addition, there are other units have been developed, di- or polycarboxylic oxide aerogels, organic aerogels and carbon aerogels. As means for preparing a unique material related processes are widely used, as the preparation of a high porosity of the porous silicon in the development of other new materials, the preparation of high performance metal catalyst – airgel composite material, high temperature superconducting material, ultra-fine ceramic powder.
2013 international study on airgel materials mainly in Germany\’s University of Würzburg, BASF Corporation, USA Lorenz · Liverpool Livermore National Laboratory, Sandia national laboratory, materials Research Center, Montpellier, France, Japan and so on High Energy Physics national laboratory. China mainly concentrated in the solid Boer Tongji University Physics Laboratory, National University of Defense Technology, Tsinghua University, Zhejiang University, Harbin Institute of Technology, Nano Technology Co., Ltd. andAlison Guangdong high-tech Co., Ltd.
Aerogels other purposes
1, making Mars exploration spacesuit
In 2002, NASA set up a company to produce stronger more resilient airgel. NASA has determined that in 2013, when the 2018 Mars Exploration, astronauts will wear the suit with the new airgel manufactured. The company\’s senior scientist Mark Kela Jie Jaworski said, just add a layer of airgel 18 mm thick spacesuit, then it will be able to help astronauts Kangzhu 1300 ℃ high temperature and ultra-low temperature of minus 130 ℃. \”This is the most efficient thermostat material I\’ve ever seen.\” Mark says.
2, bulletproof blown afraid
is a second important application ballistic novel aerogels. NASA The company is built on the airgel residence and military vehicles for testing. The laboratory test situation of view, if the rate of 6 mm thick layer of airgel in the metal sheet, so, even if the direct bombed explosives, metal sheets can be divided without injury.
3 can handle ecological disaster
an important role in environmental protection is the third new airgel. Scientists airgel affectionately known as \”super-sponge\” because its surface millions of small holes, so is the ideal material pollutants in water adsorption. US scientists airgel new invention actually be able to suck out the lead and mercury in the water. According to the scientists, this is an excellent material handling airgel ecological disaster, say in 1996, \”Sea Express\” tanker sank 72,000 tons of crude oil leaked, if this material was to spend, then do not It will cause the entire coast is severely polluted.
4, hitting a tennis racket stronger
The new aerogels also will enter our daily life for everyone in the future. Dunlop sports equipment such as the US company has successfully developed a tennis racket containing airgel. The ability to hit the ball stronger tennis rackets; early 2012, 66-year-old Bob Stoker became the first Englishman airgel for housing: \”The heat insulation effect is very good, I will air-conditioning temperature dropped 5 ℃, the results of the room temperature is still very comfortable. \”climbers to use airgel full of hope. British mountaineer Anne Parr Clement wore the shoes during the 2011 Everest is the use of airgel material part of his sleepBag also has a layer of new material.
Polymer Zhejiang University Professor Gao Chao research group prepared a lightweight airgel. It set a record lightest material in the world, with high elasticity and strong oil-absorbing ability. This solid material is referred to as \”all carbon airgel\” a density of 0.16 milligrams per cubic centimeter (throws air density), the density of air is only 1/6. Experts, airgel is the lightest Guinness World Record of a class of substances, because there are a lot of internal voids filled with air, hence the name. In 1931, American scientists won the first airgel, nicknamed \”frozen smoke\” silica system. In 2011, the United States HRL Laboratory, University of California, Irvine and Caltech collaborated airgel preparation consisting of nickel, a density of 0.9 mg / cc, setting a record at that time the lightest materials. This material is placed on the dandelion flowers, soft hairs almost no distortion. Our graphite reserves are very rich, two-thirds of the world. Science researchers have been exploring ways of efficient use of graphite. \”Graphite into a graphene (constructed by a single layer sheet-like structure of carbon atoms), which may increase the value of thousands of times.\” After exploring superb research group of five or six years, was prepared in a one-dimensional graphene fibers and two-dimensional graphene films. We intend to make three-dimensional porous material graphene to break the record this American scientists.
production is simple, its shape, size can be adjusted
in the world, have been born of the outcome, the Task Force prepared the superb \”carbon sponge\” is still the lightest record holder. Up to 0.16 mg / cc lower than the density of the helium gas.
may be manufactured in large scale
scientists claim that the basic principles of preparation of the airgel is to remove the solvent in the gel, allowing it to remain intact skeleton. In the case of a conventional airgel, scientists mainly sol – gel method and template-directed method. The former can be synthesized batch, but poor controllability; the latter can produce ordered structure, but dependent on the size of the template and a fine structure is difficult to prepare a large amount. Superb TF another way, no template explored freeze drying: dissolving an aqueous solution lyophilized graphene and carbon nanotubes at a low temperature, it is obtained a \”carbon sponge\”, and the shape can be adjusted to make the production process more convenient, this also makes large-scale manufacture and application of ultra-light materials possible.
superior performance, high flexibility, strong adsorption, wide application prospect
According to experts, the \”carbon sponge\” with a high elasticity, are compressed still restitution 80%. It organic solvent having a fast, ultra-high suction force, a suction force is the highest reported to date materials. Existing products are generally only suck the liquid oil absorption of about 10 times its own mass, and the \”carbon sponge\” absorption amount of about 250 times, up to 900 times, and only oil absorbent. \”Big eaters\” to eat organics fast: such a \”carbon sponge\” to absorb 68.8 grams per gram of organic matter per second. 20 century, the laboratory is studying further applications of the adsorption properties of this material. Researchers claim that \”carbon sponge\” may also be desirable to phase change thermal insulation material, the catalytic support, the sound absorbing material and a composite material efficiently. But it is difficult to accurately predict its field of application and prospects, had to rely on the imagination of the industry and society, so that this new material out of the laboratory to application value.