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Characteristics and uses of nanomaterials

Edit: Ccdanni 2020-01-23 Mobile

  Characteristics of nano materials:

  When the size of the particles is reduced to the nanometer level, the acoustic, optical, electrical, magnetic, and thermal properties will show new characteristics. For example, the widely studied II-VI semiconductor cadmium sulfide, its absorption band boundary and the position of the peak of the emission spectrum will be significantly blue-shifted as the grain size decreases. According to this principle, cadmium sulfide with different energy gaps can be obtained by controlling the grain size, which will greatly enrich the research content of materials and hope to obtain new applications.

  We know that the types of materials are limited. Micron and nanometer cadmium sulfide are composed of sulfur and cadmium. However, by controlling the preparation conditions, materials with different band gaps and luminous properties can be obtained. In other words, new materials have been obtained through nanotechnology.

  Nanoparticles often have a large specific surface area, and the specific surface area per gram of this solid can reach hundreds or even thousands of square meters, which makes them useful as highly active adsorbents and catalysts in hydrogen storage, organic synthesis, and environmental protection. And other fields have important application prospects. For nanobody materials, we can use the words "lighter, taller and stronger" to summarize.

  "Lighter" means that with the help of nanomaterials and technologies, we can make devices with smaller volumes and constant or better performance, reducing the size of the device and making it lighter. The first computer required three houses to store it, and it was precisely through the use of micron-level semiconductor manufacturing technology that it was miniaturized and computers became popular.

  From the perspective of energy and resource utilization, the benefits of this "miniaturization" are very amazing. "Higher" means that nanomaterials are expected to have higher optical, electrical, magnetic, and thermal properties. "Stronger" means that nanomaterials have stronger mechanical properties (such as strength and toughness). For nanoceramics, nanotechnology is expected to solve the brittleness of ceramics and may exhibit similar plasticity as materials such as metals.

  Uses of nanomaterials:

  The application prospects of nanomaterials are very broad, such as: nanoelectronic devices, medicine and health, aerospace, aviation and space exploration, environment, resources and energy, biotechnology and so on. We know that gene DNA has a double helix structure, and the diameter of this double helix structure is about tens of nanometers.

  Using synthetic light-emitting semiconductor grains with a grain size of only a few nanometers, selective adsorption or action on different base pairs can "illuminate" the structure of DNA, a bit like a pagoda full of lanterns in the dark. With the glowing "lantern", we can identify not only the appearance of the lighthouse, but also the structure of the lighthouse.

  In short, these nanocrystals are labeled with DNA molecules. At present, we should avoid the vulgarization of nanometers. Although some scientists have been studying the application of nanomaterials, many technologies are still difficult to directly benefit human beings. Since 2001, there are also some nano enterprises and nano products in China, such as "nano refrigerators" and "nano washing machines".

  Some "nano powders" are used in these products, but the core role of refrigerators and washing machines is the same as any traditional product. "Nano powders" have given them some new functions, but they are not the core technology of such products.

  Therefore, this type of product cannot be called a real "nano product", it is a sales method and a new selling point for merchants. At this stage, the application of nanomaterials is mainly concentrated on nanometer powder. It belongs to the initial stage of nanometer materials. It should be pointed out that this is only the initial stage of nanometer material application. The "application" is equivalent to nanomaterials.

  Extended information:

  Applications of nanomaterials

  1.Natural nanomaterials

  Turtles lay their eggs on the coast of Florida, but young turtles need to swim to the sea near Britain in order to survive and grow up in search of food. Finally, the grown turtles will return to the Florida coast to lay their eggs. It takes about 5 to 6 years to go back and forth in this way. Why can turtles make long journeys of tens of thousands of kilometers? They rely on nano-magnetic materials inside the head to navigate them accurately.

  Biologists studying why pigeons, dolphins, butterflies, bees and other creatures never lost their way, also discovered that nanomaterials also exist in these organisms to navigate them.

  2.Nano magnetic materials

  Most of the nanomaterials used in practice are artificially manufactured. Nano magnetic materials have very special magnetic properties. The size of the nanoparticles is small, and they have the characteristics of single magnetic domain structure and high coercivity. The magnetic recording material made of it not only has good sound quality, image and signal-to-noise ratio, but also records The density is dozens of times higher than γ-Fe2O3. Superparamagnetic ferromagnetic nanoparticles can also be made into magnetic liquids, which are used in the fields of electroacoustic devices, damping devices, rotary seals, lubrication and beneficiation.

  3. Nano-ceramic materials

  In traditional ceramic materials, the crystal grains are not easy to slide, the material is brittle, and the sintering temperature is high. The nano-ceramic has a small grain size and the crystal grains are easy to move on other grains. Therefore, the nano-ceramic material has extremely high strength and toughness and good ductility. These characteristics enable the nano-ceramic material to be used at normal or sub-high temperature Perform cold working. If the nano-ceramic particles are processed and shaped at sub-high temperature, and then surface annealing is performed, the nano-material can be made into a kind of surface that maintains the hardness and chemical stability of conventional ceramic materials, while still having the high performance of nano-material ductility inside. ceramics.

  4.Nano sensors

  Ceramics such as nano-zirconia, nickel oxide, and titanium dioxide are very sensitive to temperature changes, infrared rays, and automobile exhaust. Therefore, they can be used to make temperature sensors, infrared detectors and automobile exhaust gas detectors, with a detection sensitivity much higher than that of ordinary similar ceramic sensors.

  5.Nano-tilt functional materials

  In aerospace hydrogen-oxygen engines, the inner surface of the combustion chamber needs to be resistant to high temperatures, and its outer surface must be in contact with the coolant. Therefore, the inner surface is made of ceramics, and the outer surface is made of metal with good thermal conductivity. But massive ceramics and metals are difficult to combine.

  If the composition between metal and ceramic is gradually and continuously changed during production, let metal and ceramic "you have me, you have me", and finally they can be combined to form a tilted functional material, which means that The composition changes like a sloping ladder. When metal and ceramic nanoparticles are mixed and sintered according to the requirements of gradually changing their content, the requirements of high temperature resistance inside the combustion chamber and good thermal conductivity on the outside can be achieved.

  6.Nano-semiconductor materials

  Nano materials made of semiconductor materials such as silicon and gallium arsenide have many excellent properties. For example, the quantum tunneling effect in nano-semiconductors makes the electronic transport of certain semiconductor materials abnormal, the electrical conductivity decreases, and the electrical thermal conductivity also decreases with decreasing particle size, and even negative values appear. These characteristics play an important role in large-scale integrated circuit devices, optoelectronic devices, and other fields.

  The use of semiconductor nanoparticles can produce a new type of solar cell with high photoelectric conversion efficiency and can work normally even in rainy and rainy days. Because the electrons and holes generated by the nano-semiconductor particles when exposed to light have strong reducing and oxidizing capabilities, they can oxidize toxic inorganic substances, degrade most organic substances, and eventually generate non-toxic, odorless carbon dioxide, water, etc., Semiconductor nanoparticles can be used to catalyze the decomposition of inorganic and organic substances with solar energy.

  7.Nanocatalytic materials

  Nanoparticles are an excellent catalyst. This is due to the small size of the nanoparticles, the large volume fraction on the surface, the chemical bond states and electronic states of the surface are different from the interior of the particle, and the surface atom coordination is incomplete. Make it have the basic conditions as a catalyst.

  Nanoparticles of nickel or copper-zinc compounds are excellent catalysts for the hydrogenation of certain organics and can replace expensive platinum or palladium catalysts. Nanometer platinum black catalyst can reduce the temperature of ethylene oxidation reaction from 600 ℃ to room temperature.

  8. Medical applications

  The size of red blood cells in the blood is 6 000-9 000 nm, and the nanoparticles are only a few nanometers in size, which is actually much smaller than red blood cells, so it can move freely in the blood. If various kinds of therapeutic nanoparticles are injected into various parts of the human body, the lesions can be inspected and treated. The effect is better than the traditional injection and medicine.

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