What is plasma?
Edit the introduction of this paragraph.
Plasma state means that the electrons in the atoms of a substance are separated from the attraction of the nucleus at high temperature, so that the substance exists in the state of positive and negative charged particles.
Edit this specific introduction about plasma.
Plasma state is a ubiquitous state. Most luminous planets in the universe have high internal temperature and pressure, and almost all the materials inside these planets are in plasma state. Solid, liquid and gaseous matter can only be found in dim planets and scattered interstellar matter. Plasma is widely used. From our daily life to industry, agriculture, environmental protection, military, aerospace, energy, celestial bodies and other aspects, it has very important application value. The plasma state makes the electrons in the atoms of the substance escape from the attraction of the nucleus at high temperature, so that the substance exists in the state of positive and negative charged particles. In our daily life, we will encounter all kinds of substances. According to their state, they can be divided into three categories, namely, solid, liquid and gas. For example, steel is solid, water is liquid and oxygen is gas. Under certain conditions, any substance can change between these three states. Take water as an example. At standard atmospheric pressure, when the temperature drops below 0℃, water begins to turn into ice. When the temperature rises to 0℃, it will turn into ice. Scientists tell us that at this time, the atoms that make up the molecule split into independent atoms. For example, a nitrogen molecule will split into two nitrogen atoms. We call this process the dissociation of gas molecules. If the temperature rises further, the electrons in the atom will be separated from the atom and become positively charged nuclei and negatively charged electrons. This process is called atomic ionization. When this ionization process occurs frequently and the concentration of electrons and ions reaches a certain value, the state of matter changes fundamentally and its properties become completely different from those of gas. In order to distinguish it from solid, liquid and gas, we call this state of matter the fourth state of matter, also called plasma state. Around us, we often see substances in plasma. It can be found in fluorescent lamps and neon lamps, as well as in dazzling incandescent arcs. In addition, in the ionosphere around the earth, in the beautiful aurora, in the flash discharge in the atmosphere and in the tail of a meteor, wonderful plasma states can also be found.
Edit this plasma state
In the vast universe, plasma state is a ubiquitous state. Most luminous planets in the universe have high internal temperature and pressure, and almost all the materials inside these planets are in plasma state. Solid, liquid and gaseous matter can only be found in dim planets and scattered interstellar matter. Around us, we often see plasma substances. It can be found in fluorescent lamps and neon lamps, as well as in dazzling incandescent arcs. In addition, in the ionosphere around the earth, in the beautiful aurora, in the flash discharge in the atmosphere and in the tail of a meteor, wonderful plasma states can also be found.
concept
When this ionization process occurs frequently and the concentration of electrons and ions reaches a certain value, the state of matter changes fundamentally and its properties become completely different from those of gas. In order to distinguish it from solid, liquid and gas, we call this state of matter the fourth state of matter, also called plasma state.
trait
Substances in plasma state have similar properties as gaseous substances, such as good fluidity and diffusivity. However, because the basic particles of plasma are ions and electrons, it also has many properties different from gases, such as good electrical conductivity and thermal conductivity. Especially according to scientific calculation, the specific heat of plasma is directly proportional to temperature, and the specific heat of plasma at high temperature is often hundreds of times that of gas.
use
What is the use of plasma? Oh! It has a wide range of uses. From our daily life to industry, agriculture, environmental protection, military, medicine, aerospace, energy, celestial bodies and other aspects, it has very important application value.
plasma cutting machine
Industrial applications include plasma cutting machines, which can use different working gases.
Cutting all kinds of metals that are difficult to be cut by oxygen, especially non-ferrous metals (stainless steel, aluminum, copper, titanium, nickel); Its main advantage is that the plasma cutting speed is fast when cutting metal with small thickness, especially when cutting ordinary carbon steel sheet, the speed can reach 5~6 times that of oxygen cutting method, the cutting surface is smooth, the thermal deformation is small, and there is almost no heat affected zone. An important research is high temperature plasma and controlled thermonuclear fusion reaction. If the lightest element in matter, such as deuterium, is used to form a high-temperature plasma of tens of millions of degrees Celsius, then these nuclei will have a nuclear reaction. As a result, huge energy will be released, which scientists call thermonuclear fusion reaction. The hydrogen bomb is such an explosive thermonuclear fusion reaction. Humans hope to have a thermonuclear fusion reaction that can slowly release energy to generate electricity and build an "artificial little sun".
Edit this paragraph, plasma welding machine
Plasma arc is a high-temperature ion gas stream generated by ionization of ion gas, which is ejected from nozzle holes and covered with TIG after plasma suppression.
Shrinking into a slender arc column, its temperature can reach 18000-24000K, which is higher than that of conventional free arc. For example, argon arc welding only reaches 5000-8000K K, and plasma arc is widely used in welding field because of its slender arc column and high energy density. Plasma welding machine has the following obvious characteristics: 1 High-efficiency and high-quality plasma welding process method, using the good keyhole penetration ability of plasma arc, while ensuring one-sided welding and double-sided forming, the welding speed is increased as much as possible, which is 5~7 times of TIG welding efficiency. Using plasma and TIG composite welding, plasma backing and TIG covering can improve welding quality and efficiency more effectively. The free arc of TIG welding has a good covering ability, and with a proper amount of filler metal remelting, the effect of beautiful front forming is achieved, which is 1.3- 1.5 times of the efficiency of single gun plasma welding. It is mainly used for longitudinal girth welding of thin-walled 3~ 10mm stainless steel plates, titanium alloy plates and other material containers. For stainless steel plates with a wall thickness less than 8mm and a wall thickness of 10,
Edit the paragraph of stealth plane.
Another important application is that some special chemical elements form low-temperature plasma, whose macro temperature is not high, but the electron temperature can reach tens of thousands of degrees Celsius. At this time, special chemical reactions will occur between substances. Therefore, it can be used to develop new materials, such as coating a thin layer of titanium nitride on tools such as drill bits to improve the strength of tools, manufacturing solar cells, and coating a layer of materials specially absorbing radar waves on the surface of aircraft (that is, stealth aircraft) to avoid radar tracking ... These are called plasma thin film technologies. In addition, plasma can also be used to remove sulfur from smoke and dust, improve crop yield by irradiating seeds with plasma, develop large-screen plasma TV sets, and develop plasma rocket engines to distant places such as Mars. In addition, plasma has also been paid attention to in medical surgical treatment, such as plasma cryoablation, which is popular in recent years to treat rhinitis, pharyngitis, snoring and other diseases. The principle of cryoplasma ablation is to form a thin plasma layer between the electrode and the tissue. Ions in this layer are accelerated by the electric field and energy is transferred to the tissue. At low temperature (40℃-70℃), the molecular binding bonds between cells are opened, so that the cells in the target tissue are decomposed into carbohydrates and oxides, causing liquefaction and ablation of the diseased tissue. This phenomenon is called plasma (non-thermal effect), thus achieving the effect of volume reduction of the target tissue.
Edit this plasma display and TV.
Plasma TV PDP (plasma display panel) is a wall-mounted plasma TV with mixed gas injected between two ultra-thin glass plates.
Equipment for applying voltage to make use of fluorescent powder to emit light and image. A mixed gas is filled between thin glass plates, a voltage is applied to generate ion gas, and then plasma gas is discharged to react with phosphor in the substrate, thereby generating a color image. Plasma color TV, also known as "wall-hung TV", is not affected by magnetic force and magnetic field, and has the advantages of slim body, light weight, large screen, bright color, clear picture, high brightness, small distortion and space saving. Plasma is a new generation of display equipment which is developed rapidly in recent years and adopts plasma flat panel technology. At present, there are two kinds of products on the market, one is plasma display screen and the other is plasma TV. There is not much difference between the two in essence. The only difference is whether there is a built-in tv receiving tuner. Because PDP was mainly used for commercial display in the early stage of development, there are still many PDPs that don't have built-in tv receiving tuners, that is, they can't receive TV signals directly. Therefore, if you choose this product, you can only use other devices such as satellite decoder or video recorder as TV signal tuning receiver, or you can buy another TV receiver. Now the plasma has been designed and produced for home users, and some of the plasma produced at present has started to be built-in tv receiver. These models are equipped with RF connection terminals in advance, which can directly play TV programs. Most domestic PDPs are built-in tv receivers, such as Hisense, SVA and TCL. And foreign manufacturers, some products use external TV receivers, and some products use built-in tv receivers. Generally, the PDP of external TV receiver is called plasma display screen, and the PDP of built-in tv receiver is called plasma TV. When purchasing, you should ask whether it has TV reception function. Plasma display panel (PDP) is a display device using gas discharge. This screen uses a plasma chamber as a light-emitting element. A large number of plasma chambers are arranged together to form a screen. The screen of plasma display screen consists of two glass plates separated by hundreds of microns, which are isolated from the air. Inert gases such as neon and xenon are filled in each plasma cavity, and the gas in the plasma cavity sealed between two pieces of glass will generate ultraviolet light, thus exciting the red, green and blue phosphors on the flat panel display screen to emit visible light. As a pixel, the working mechanism of each ion cavity is similar to that of ordinary fluorescent lamps. The combination of brightness and color changes of these pixels produces images of various brightness and color, while TV color images are synthesized by the illumination of a single pixel.
trait
Compared with the traditional CRT TV, the most prominent feature of plasma (PDP) TV is "big and thin", and other features are: (1) light and thin structure. Because the PDP display module is light and thin, it determines the corresponding structural characteristics of the whole display screen, and the increase of display size does not need to increase the thickness of the screen body accordingly. (2) Wide viewing angle. PDP can achieve the same wide viewing angle as CRT, which is greater than 160 degrees. The viewing angle of liquid crystal (LCD) is generally left 120 degrees in horizontal direction, and even less in vertical direction. (3) Anti-electromagnetic interference. Due to the different display principles, external electromagnetic interference, such as motors and speakers, has little effect on the image of PDP. In contrast, the interference of CRT by electromagnetic field is much more obvious. (4) The plane image has no distortion. The RGB grid of PDP is evenly distributed on the plane, while the inner surface of flat CRT is uneven, which will cause typical pincushion distortion. However, when the local brightness of the picture is uneven, CRT often produces corresponding image distortion, while PDP does not. (5) There is no problem of convergence and focusing. Plasma TV is a high-tech, cutting-edge electronic product that many customers are not familiar with. Many people are cautious when using it because they don't understand its principle, so they can't fully enjoy the enjoyment brought by plasma TV. In fact, the service life of plasma TV sets is about twice that of ordinary TV sets. If the service life of an ordinary TV set is 10 years, the plasma can be used for about 20 years, and the plasma TV set is superior to the ordinary TV set in many aspects, such as display, color and appearance, so the plasma TV set is the development direction of the future TV set.
principle of operation
It is a display technology using gas discharge, and its working principle is very similar to that of fluorescent lamp. It uses plasma tubes as light-emitting elements, and each plasma tube on the screen corresponds to a pixel. The screen takes glass as the substrate, and the substrates are separated by a certain distance, and the surrounding is sealed to form a discharge space. The discharge space is filled with a mixed inert gas such as neon and xenon as a working medium. Luminous principle of PDP (working principle of plasma display panel)
The inner surfaces of the two glass substrates are coated with metal oxide conductive films as excitation electrodes. When a voltage is applied to the electrode, plasma discharge occurs in the mixed gas in the discharge space. The gas plasma discharge generates ultraviolet rays, which excite the fluorescent screen, and the fluorescent screen emits visible light to display images. When a phosphor screen coated with three primary colors (also known as three primary colors) is used, ultraviolet rays excite the phosphor screen, and the light emitted by the phosphor screen is red, green and blue. When each primary color unit reaches 256 gray levels, color mixing is carried out to realize color display. According to its working mode, plasma display technology can be divided into two categories: DC PDP with electrodes in direct contact with gas and AC PDP with electrodes covered with dielectric layer. At present, there are three main types of color PDP: single substrate (also known as surface discharge) AC PDP, double substrate (also known as reverse discharge) AC PDP and pulse storage DC PDP.
Edit this plasma surgery system.
The technology of "plasma" is to generate plasma with a specific ultra-low frequency excitation medium (Nacl) of 100Khz. High-speed charged particles in the plasma directly destroy molecular bonds, and protein and other tissues are pyrolyzed and vaporized into low-molecular-weight gases, such as H2, O2, CO2, N2 and methane. Under the variable electric field of common high frequency of 500-4000KHz, on the one hand, the particles can not get enough acceleration time and are in a reciprocating oscillation state; On the other hand, the intensified molecular friction at high frequency will produce strong thermal effect, and the higher the frequency, the more heat will be generated. However, under the low-frequency stable electric field of 100KHz, the particles will get a longer acceleration time, and eventually form high-speed charged particles with greater kinetic energy, which directly breaks the molecular bonds. In addition, due to the low frequency, compared with high frequency, the heat generated by friction between molecules is greatly reduced, so that the cutting, ablation and hemostasis processes are all completed within 40℃~70℃, thus achieving minimally invasive effect. Electrosurgical equipment has gone through the development stages from low to high: electrosurgical unit, common radio frequency and plasma radio frequency. Plasma technology has completely changed the traditional working modes of "radio frequency" and "heat energy" through direct vaporization. Tissue vaporization at 40℃~70℃ replaces the traditional process of "cutting" and "hemostasis", which greatly reduces the trauma in surgery. The minimally invasive function of "plasma" technology in clinical treatment is the trend of future medical development.