Characteristics of nanomaterials:
When the particle size is reduced to the nanometerscale, it will lead to new characteristics of acoustic, optical, electrical, magnetic and thermal properties. For example, the position of the absorption band boundary and the peak of the luminescence spectrum of the widely studied group II-VI semiconductor cadmium sulfide will be significantly blue shifted with the decrease of grain size. 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 is expected to get new uses.
We know that the types of substances are limited, micron and nano cadmium sulfide are composed of sulfur and cadmium elements, but by controlling the preparation conditions, you can get different band-gap and luminous properties of materials. In other words, completely new materials have been created through nanotechnology.
Nanoparticles often have a large specific surface area, the specific surface area of each gram of this solid can reach hundreds or even thousands of square meters, which makes them can be used as highly active adsorbents and catalysts, and have important application prospects in the fields of hydrogen storage, organic synthesis and environmental protection. For nano-body materials, we can use the six words \"lighter, higher, stronger\" to summarize.
\"Lighter\" means that with the help of nanomaterials and technology, we can prepare smaller devices with the same performance or even better, reduce the volume of the device, and make it lighter. The first computer required three rooms to store, and it was with the help of micron-scale semiconductor manufacturing technology that it was miniaturized and popularized computers.
Both in terms 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, etc.), for nano-ceramics, nanization is expected to solve the brittleness problem of ceramics, and may show similar plasticity with metals and other materials.
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 genetic DNA has a double helix structure, which is about tens of nanometers in diameter.
With synthetic luminous semiconductor grains whose grain size is only a few nanometers, selective adsorption or action on different base pairs can \"illuminate\" the structure of DNA, a bit like a pagoda with lanterns in the dark, with the luminous \"lantern\
In short, these nanocrystals attach a label to the DNA molecule. For now, we should avoid the vulgarization of nano. Although scientists have been studying the application of nanomaterials, many technologies are still difficult to directly benefit humans. Since 2001, there have also been some nano enterprises and nano products in China, such as \"nano refrigerator\" and \"nano washing machine\".
These products use some \"nano powder\
Therefore, such products can not be called real \"nano products\
Application range of nanomaterials
1. Natural nanomaterials
Sea turtles lay their eggs on the coast of Florida in the United States, but after birth, the young turtles have to swim to the waters near the United Kingdom in order to survive and grow up. Finally, the adult turtles return to the Florida coast to lay their eggs. It takes five to six years to make the trip, so why are turtles able to travel tens of thousands of kilometers? They rely on magnetic nanomaterials inside their heads to navigate them flawlessly.
When biologists study why pigeons, dolphins, butterflies, bees and other organisms never lose their way, they also find nanomaterials in these organisms to guide them.
2, nano magnetic materials
Most of the nanomaterials used in practice are man-made. Nano-magnetic materials have very special magnetic properties, small size of nanoparticles, with a single magnetic domain structure and high coercivity characteristics, the magnetic recording materials made of it not only sound quality, image and signal to noise ratio is good, and the recording density is dozens of times higher than γ-Fe2O3. Superparamagnetic strong magnetic nanoparticles can also be made into magnetic liquids, which are used in electroacoustic devices, damping devices, rotary seals, lubrication and mineral processing.
3. Nano-ceramic materials
In traditional ceramic materials, the grain is not easy to slip, the material is brittle and the sintering temperature is high. Nano-ceramic grain size is small, the grain is easy to move on other grains, therefore, nano-ceramic materials have extremely high strength and high toughness and good ductility, these characteristics make nano-ceramic materials can be cold processed at room temperature or sub-high temperature. If the nano-ceramic particles are processed and formed at sub-high temperatures, and then the surface annealing treatment is done, the nanomaterial can be made into a high-performance ceramic whose surface maintains the hardness and chemical stability of conventional ceramic materials, while the interior still has the ductility of nanomaterial.
4. Nanosensors
Nano-zirconia, nickel oxide, titanium dioxide and other ceramics 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 detectors, and the detection sensitivity is 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 temperature, and the outer surface needs to be in contact with the coolant. Therefore, the inner surface should be made of ceramic, and the outer surface should be made of metal with good thermal conductivity. But lumpy ceramics and metals are difficult to combine.
If the composition is gradually changed continuously between the metal and the ceramic during production, so that the metal and the ceramic \"you have me, I have you\" can eventually be combined to form a tilted functional material, which means that the composition changes like a tilted ladder. When metal and ceramic nanoparticles are mixed and sintered according to the requirements of gradually changing content, the requirements of high temperature resistance on the inside of the combustion chamber and good thermal conductivity on the outside can be achieved.
6, nano semiconductor materials
Nanomaterials made from semiconductor materials such as silicon and gallium arsenide have many excellent properties. For example, the quantum tunneling effect in nanosemiconductors makes the electron transport of some semiconductor materials abnormal, the electrical conductivity decreases, and the electrical thermal conductivity decreases with the decrease of particle size, and even appears negative. These characteristics play an important role in the field of large-scale integrated circuit devices, optoelectronic devices and so on.
Semiconductor nanoparticles can be used to produce a new type of solar cell with high photoelectric conversion efficiency, which can work normally even in rainy days. Because the electrons and holes produced by the nano semiconductor particles are irradiated by light have strong reduction and oxidation capacity, it can oxidize toxic inorganic substances, degrade most organic matter, and eventually generate non-toxic, odorless carbon dioxide, water, etc., so you can use semiconductor nanoparticles to catalyze the decomposition of inorganic substances and organic matter.
7, nano catalytic materials
Nanoparticles are an excellent catalyst, which is due to the small size of nanoparticles, the larger volume fraction of the surface, the chemical bond state and electronic state of the surface are different from the particle inside, and the incomplete coordination of the surface atoms, resulting in an increase in the active position of the surface, so that it has the basic conditions as a catalyst.
The hydrogenation of certain organics by nanoparticles of nickel or copper-zinc compounds is an excellent catalyst that can replace expensive platinum or palladium catalysts. The nano-platinum black catalyst can reduce the temperature of ethylene oxidation from 600 ℃ to room temperature.
8. Medical applications
The size of the red blood cells in the blood is 6 000 to 9 000 nm, while the nanoparticles are only a few nanometers in size, and are actually much smaller than the red blood cells, so it can move freely in the blood. If various therapeutic nanoparticles are injected into various parts of the human body, lesions can be examined and treated, and its effect is better than the traditional injection and medicine.