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"Weakness" hard carbon aerogels seem to have a lot of power

  • Categories:Industry News
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  • Time of issue:2019-06-14 13:21
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(Summary description)Recently, a research group led by Professor Shuhong Yu from the University of Science and Technology of China, inspired by the high strength and elasticity of natural spider webs, has skillfully prepared a series of hard carbon aerogels with a network structure of nanofibers through the template method. This series of aerogels has the advantages of super elasticity, fatigue resistance and good stability. The research results were selected as the back cover of the paper published in Advanced Materials. Aerogel is sometimes referred to as "solid smoke" or "frozen smoke" because of its translucent color and ultra-light weight. Aerogel looks fragile, but it's actually very strong and durable. It can withstand thousands of times its own mass and does not melt until temperatures reach 1,200 degrees Celsius. It also has low thermal conductivity and refractive index, and insulation that is 39 times stronger than the best glass fiber. Because of these properties, aerogel has become an irreplaceable material for space exploration. Both the Russian Mir space station and the American Mars Pathfinder spacecraft have used it for thermal insulation. Carbon materials can be roughly divided into graphite carbon, soft carbon and hard carbon according to the different hybrid orbitals of carbon atoms. Soft carbon and hard carbon are mainly used to describe carbon materials prepared by polymer pyrolysis. During the pyrolysis process, some carbon atoms reconstitute two-dimensional aromatic graphene sheets. If these graphene sheets are roughly parallel, they are prone to graphitization at high temperatures. If these graphene sheets are stacked randomly and cross-linked by edge carbon atoms that cannot be graphitized at high temperatures, the carbon is called hard carbon. Generally speaking, graphite carbon and soft carbon have high elasticity, easy to deformation, but low strength; Due to the existence of the "house of cards" structure on the microstructure of hard carbon, the hard carbon material shows great advantages in mechanical strength and structural stability, but the intrinsic nature is brittle and fragile. How to prepare hard carbon material into super - elastic block is a challenge at present. By using resorcine-formaldehyde (RF) resin as the hard carbon source and using a variety of one-dimensional nanofibers as the structural template, the researchers prepared RF nanofiber aerogels, which were superelastic hard carbon aerogels obtained by carbonization at high temperature. This hard carbon aerogel has a fine microstructure and is made up of a large number of nanofibers and the weld joints between them. This method is simple, efficient and easy to scale production. By adjusting the addition amount of template and resin monomer, the diameter of nanofibers, the density of aerogel and the mechanical properties of the nanofibers can be easily controlled. Unlike traditional hard carbon blocks, which are hard and brittle, this kind of hard carbon aerogel shows excellent elastic properties, such as stable structure, microstructure can still recover after compression by 50%. The rebound speed is higher than that of many graphite-carbon-based elastic materials; Low energy loss coefficient, general graphite and soft carbon materials in the existence of intermolecular forces, will cause adhesion and friction force and dissipate a lot of energy; Fatigue resistance. After 104 cycles of testing at 50% strain, the carbon aerogel showed only 2% plastic deformation and maintained 93% initial stress. The researchers have also explored the application of this hard carbon aerogel in elastic conductors where resistance is almost constant after multiple compression cycles at 50% strain, demonstrating stable mechanical-electrical properties while maintaining hyperelasticity and resistance stability under harsh conditions, such as in liquid nitrogen. Because of its excellent mechanical properties, this kind of hard carbon aerogel is expected to be used in stress sensors with high stability, large range, stretchability or bendability. In addition, this method can be extended to prepare other non-carbon based composite nanofiber aerogels, providing a new way to convert rigid materials into elastic or flexible materials by designing the microstructure of nanofibers in the future.

"Weakness" hard carbon aerogels seem to have a lot of power

(Summary description)Recently, a research group led by Professor Shuhong Yu from the University of Science and Technology of China, inspired by the high strength and elasticity of natural spider webs, has skillfully prepared a series of hard carbon aerogels with a network structure of nanofibers through the template method. This series of aerogels has the advantages of super elasticity, fatigue resistance and good stability. The research results were selected as the back cover of the paper published in Advanced Materials.



Aerogel is sometimes referred to as "solid smoke" or "frozen smoke" because of its translucent color and ultra-light weight. Aerogel looks fragile, but it's actually very strong and durable. It can withstand thousands of times its own mass and does not melt until temperatures reach 1,200 degrees Celsius. It also has low thermal conductivity and refractive index, and insulation that is 39 times stronger than the best glass fiber. Because of these properties, aerogel has become an irreplaceable material for space exploration. Both the Russian Mir space station and the American Mars Pathfinder spacecraft have used it for thermal insulation.



Carbon materials can be roughly divided into graphite carbon, soft carbon and hard carbon according to the different hybrid orbitals of carbon atoms. Soft carbon and hard carbon are mainly used to describe carbon materials prepared by polymer pyrolysis. During the pyrolysis process, some carbon atoms reconstitute two-dimensional aromatic graphene sheets. If these graphene sheets are roughly parallel, they are prone to graphitization at high temperatures. If these graphene sheets are stacked randomly and cross-linked by edge carbon atoms that cannot be graphitized at high temperatures, the carbon is called hard carbon.



Generally speaking, graphite carbon and soft carbon have high elasticity, easy to deformation, but low strength; Due to the existence of the "house of cards" structure on the microstructure of hard carbon, the hard carbon material shows great advantages in mechanical strength and structural stability, but the intrinsic nature is brittle and fragile. How to prepare hard carbon material into super - elastic block is a challenge at present.



By using resorcine-formaldehyde (RF) resin as the hard carbon source and using a variety of one-dimensional nanofibers as the structural template, the researchers prepared RF nanofiber aerogels, which were superelastic hard carbon aerogels obtained by carbonization at high temperature. This hard carbon aerogel has a fine microstructure and is made up of a large number of nanofibers and the weld joints between them. This method is simple, efficient and easy to scale production. By adjusting the addition amount of template and resin monomer, the diameter of nanofibers, the density of aerogel and the mechanical properties of the nanofibers can be easily controlled.



Unlike traditional hard carbon blocks, which are hard and brittle, this kind of hard carbon aerogel shows excellent elastic properties, such as stable structure, microstructure can still recover after compression by 50%. The rebound speed is higher than that of many graphite-carbon-based elastic materials; Low energy loss coefficient, general graphite and soft carbon materials in the existence of intermolecular forces, will cause adhesion and friction force and dissipate a lot of energy; Fatigue resistance. After 104 cycles of testing at 50% strain, the carbon aerogel showed only 2% plastic deformation and maintained 93% initial stress.



The researchers have also explored the application of this hard carbon aerogel in elastic conductors where resistance is almost constant after multiple compression cycles at 50% strain, demonstrating stable mechanical-electrical properties while maintaining hyperelasticity and resistance stability under harsh conditions, such as in liquid nitrogen.



Because of its excellent mechanical properties, this kind of hard carbon aerogel is expected to be used in stress sensors with high stability, large range, stretchability or bendability. In addition, this method can be extended to prepare other non-carbon based composite nanofiber aerogels, providing a new way to convert rigid materials into elastic or flexible materials by designing the microstructure of nanofibers in the future.

  • Categories:Industry News
  • Author:
  • Origin:
  • Time of issue:2019-06-14 13:21
  • Views:

Recently, a research group led by Professor Shuhong Yu from the University of Science and Technology of China, inspired by the high strength and elasticity of natural spider webs, has skillfully prepared a series of hard carbon aerogels with a network structure of nanofibers through the template method. This series of aerogels has the advantages of super elasticity, fatigue resistance and good stability. The research results were selected as the back cover of the paper published in Advanced Materials.

Aerogel is sometimes referred to as "solid smoke" or "frozen smoke" because of its translucent color and ultra-light weight. Aerogel looks fragile, but it's actually very strong and durable. It can withstand thousands of times its own mass and does not melt until temperatures reach 1,200 degrees Celsius. It also has low thermal conductivity and refractive index, and insulation that is 39 times stronger than the best glass fiber. Because of these properties, aerogel has become an irreplaceable material for space exploration. Both the Russian Mir space station and the American Mars Pathfinder spacecraft have used it for thermal insulation.

Carbon materials can be roughly divided into graphite carbon, soft carbon and hard carbon according to the different hybrid orbitals of carbon atoms. Soft carbon and hard carbon are mainly used to describe carbon materials prepared by polymer pyrolysis. During the pyrolysis process, some carbon atoms reconstitute two-dimensional aromatic graphene sheets. If these graphene sheets are roughly parallel, they are prone to graphitization at high temperatures. If these graphene sheets are stacked randomly and cross-linked by edge carbon atoms that cannot be graphitized at high temperatures, the carbon is called hard carbon.

Generally speaking, graphite carbon and soft carbon have high elasticity, easy to deformation, but low strength; Due to the existence of the "house of cards" structure on the microstructure of hard carbon, the hard carbon material shows great advantages in mechanical strength and structural stability, but the intrinsic nature is brittle and fragile. How to prepare hard carbon material into super - elastic block is a challenge at present.

By using resorcine-formaldehyde (RF) resin as the hard carbon source and using a variety of one-dimensional nanofibers as the structural template, the researchers prepared RF nanofiber aerogels, which were superelastic hard carbon aerogels obtained by carbonization at high temperature. This hard carbon aerogel has a fine microstructure and is made up of a large number of nanofibers and the weld joints between them. This method is simple, efficient and easy to scale production. By adjusting the addition amount of template and resin monomer, the diameter of nanofibers, the density of aerogel and the mechanical properties of the nanofibers can be easily controlled.

Unlike traditional hard carbon blocks, which are hard and brittle, this kind of hard carbon aerogel shows excellent elastic properties, such as stable structure, microstructure can still recover after compression by 50%. The rebound speed is higher than that of many graphite-carbon-based elastic materials; Low energy loss coefficient, general graphite and soft carbon materials in the existence of intermolecular forces, will cause adhesion and friction force and dissipate a lot of energy; Fatigue resistance. After 104 cycles of testing at 50% strain, the carbon aerogel showed only 2% plastic deformation and maintained 93% initial stress.

The researchers have also explored the application of this hard carbon aerogel in elastic conductors where resistance is almost constant after multiple compression cycles at 50% strain, demonstrating stable mechanical-electrical properties while maintaining hyperelasticity and resistance stability under harsh conditions, such as in liquid nitrogen.

Because of its excellent mechanical properties, this kind of hard carbon aerogel is expected to be used in stress sensors with high stability, large range, stretchability or bendability. In addition, this method can be extended to prepare other non-carbon based composite nanofiber aerogels, providing a new way to convert rigid materials into elastic or flexible materials by designing the microstructure of nanofibers in the future.

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Working principle of nitrogen making machine

PSA pressure swing adsorption nitrogen production mechanism nitrogen principle Carbon molecular sieve can absorb oxygen and nitrogen in the air at the same time, and its adsorption capacity also increases with the increase of pressure, and at the same pressure oxygen and nitrogen equilibrium adsorption capacity has no obvious difference. Therefore, it is difficult to complete the effective separation of oxygen and nitrogen only by the change of pressure. If further consideration is given to adsorption rates, the adsorption properties of oxygen and nitrogen can be effectively distinguished. The diameter of oxygen molecules is smaller than that of nitrogen molecules, so the diffusion rate is hundreds of times faster than that of nitrogen, so the speed of carbon molecular sieve adsorption of oxygen is also very fast, adsorption of about 1 minutes to reach more than 90%; At this time, the amount of nitrogen adsorption is only about 5%, so the adsorption is mostly oxygen, and the rest is mostly nitrogen. In this way, if the adsorption time is controlled within 1 minute, you can initially separate oxygen and nitrogen, that is to say, adsorption and desorption are achieved by pressure difference, when the pressure increases adsorption, desorption when the pressure drops. The distinction between oxygen and nitrogen is based on the adsorption speed difference between the two, through the control of adsorption time to achieve, the time control is very short, oxygen has been fully adsorbed, and nitrogen has not yet had time to adsorption, stopped the adsorption process. Therefore, pressure change and time control for nitrogen production by pressure swing adsorption should be within 1 minute.
2019-09-29

Air compressor terminology and related knowledge

(1), pressure: the pressure referred to in the compressor industry refers to pressure (P) Ⅰ, standard atmospheric pressure (ATM) Ⅱ, working pressure, suction, exhaust pressure, refers to the air compressor suction, exhaust pressure ① The pressure measured with atmospheric pressure as the zero point is called surface pressure P(G). ② The pressure with absolute vacuum as the zero point is called the absolute pressure P(A). The exhaust pressure usually given on the compressor nameplate is the gauge pressure. Ⅲ, differential pressure, pressure difference Ⅳ, loss of pressure: pressure loss Ⅴ, air compressor, the commonly used pressure unit conversion: 1MPa (MPa) =106Pa (PASCAL) 1bar (bar) =0.1MPa 1atm (standard atmospheric pressure) =1.013bar=0.1013MPa Usually in the air compressor industry, "kg" refers to "bar". (2), nominal flow: nominal flow in China is also known as the displacement or nameplate flow. Generally speaking, under the required exhaust pressure, the gas volume discharged by the air compressor per unit time is converted to the intake state, which is the volume value of the suction pressure and suction temperature and humidity at the first stage of the intake pipe. Unit time refers to one minute. That is, the suction volume Q= CM *λ*D3*N=L/D*D3N L: Length of rotor D: Diameter of the rotor N: The shaft speed of the rotor CM: Coefficient of profile line Lambda: length to diameter ratio According to the national standard, the actual exhaust volume of air compressor is ± 5% of the nominal flow. Reference state: a standard atmospheric pressure, temperature 20℃, humidity is 0℃, this reference state in the United States, Britain, Australia and other English-speaking countries T =15℃. Europe and Japan T =0℃. Standard condition: one standard atmosphere, temperature 0℃, humidity 0 If converted to base state, the unit is :m3/min (cubic per minute) If converted to standard state, the unit is :Nm3/min (standard square per minute) After 1 m/min = 1000 l/min 1 nm after/min after = 1.07 m/min (3) Oil content of gas: Ⅰ, per unit volume of compressed air in the oil (including oil, suspended particles and oil steam), the quality of the conversion to off the pressure of 0.1 MPa, temperature is 20 ℃ and relative humidity of 65% the value of the standard atmospheric conditions. Unit :mg/m3 (refers to absolute pair value) Ⅱ, PPM said a trace substances content in the mixture of symbols, refers to the number in every one million hundreds million (weight than PPMw and volume than PPMv). (referring to the ratio) Usually we refer to PPM as the weight ratio. (One millionth of a kilogram is a milligram) 1PPMW =1.2mg/m3(Pa =0.1MPa, t=20℃, φ=65%) (4) Specific power: refers to the power consumed by a certain volume flow of the compressor. It is a kind of index to evaluate the compressor performance under the same gas compression and the same exhaust pressure. Specific power = shaft power (total input power)/ exhaust (kW/m3·min-1) Shaft power: The power required to drive the shaft of the compressor. P axis =√3×U×I× COS φ(9.5)×η(98%) motor ×η drive (5), electrical and other terms Ⅰ, power: current per unit time to do the work (P), the unit is W (watt We usually use kW (kilowatt), but also horsepower (HP) 1 KW HP1HP = 1.34102 = 0.7357 KW Ⅱ, current: electronic under the action of electric field force, there are rules of move in one direction When it moves, it forms A current in A amperes. Ⅲ, voltage: just because have head and water flow, there is also a potential difference, It is called voltage (U), and the unit is V (volts). Ⅳ, phase, refers to the wire, three phase four wire: refers to the three phase thread (or wire) The center line (or zero line), single phase refers to a phase line (or fire line) Root center line (or zero line) Ⅴ, frequency: alternating current (ac) to complete the electromotive force of the positive and negative transformation cycles a second number, use (f), according to the unit - Hertz (Hz) of 50 Hz alternating current frequency in our country, abroad is 60 Hz. Ⅵ, frequency: change the frequency, in air compressor application, by changing the frequency of the power to change the speed of the motor, so as to achieve the purpose of flow adjustment. The flow rate can be adjusted to 0.1bar by frequency conversion, which greatly reduces idle work and achieves the purpose of energy saving. Ⅶ, controller: there are two main types of controller in industry: instrument type and PL System, we use PLC controller, is a kind of by A programmable controller composed of single chip microcomputer and other components. Ⅷ, straight league: direct connection, in t
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Air compressor room size design matters needing attention

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The operation of argon production in air separation unit is complicated.

Total rectification of argon is to separate oxygen from argon in a crude argon column to obtain crude argon with oxygen content less than 1×10-6 directly, and then separate it from fine argon to obtain fine argon with purity of 99.999%.   With the rapid development of air separation technology and the demand of market, more and more air separation units adopt the process of producing argon without hydrogen to produce high purity argon products. However, due to the complexity of argon production operation, many air separation units with argon did not lift argon, and some units in operation of argon system were not satisfactory due to the fluctuation of oxygen use condition and the limitation of operation level. Through the following simple steps, the operator can have a basic understanding of producing argon without hydrogen!   Commissioning of argon making system   * V766 in full opening process before discharging coarse argon column into fine argon column; Liquid blowout and discharge valves V753 and 754 at the bottom of crude argon tower I (24 ~ 36 hours). * Full opening process argon out coarse argon tower I defining argon tower valve V6; Non-condensing gas discharge valve V760 at the top of the argon tower; Precision argon tower, liquid blowing at the bottom of precision argon measuring cylinder, discharge valves V756 and V755 (precooling precision argon tower can be carried out at the same time as precooling coarse argon tower).   Check the argon pump   * Electronic control system -- wiring, control and display are correct; * Sealing gas -- whether the pressure, flow, pipeline is correct and does not leak; * Motor rotation direction -- point motor, confirm the correct rotation direction; * Piping before and after the pump -- check to make sure the piping system is smooth.   Check the argon system instrument thoroughly   (1) Rough argon tower I, Rough argon tower II resistance (+) (-) pressure tube, transmitter and display instrument is correct; (2) Whether all liquid level gauge (+) (-) pressure tube, transmitter and display instrument in argon system are correct; (3) Whether the pressure tube, transmitter and display instrument are correct at all pressure points; (4) Whether the argon flow rate FI-701 (the orifice plate is in the cold box) (+) (-) pressure tube, transmitter and display instrument are correct; ⑤ Check whether all automatic valves and their adjustment and interlocking are correct.   Main tower working condition adjustment   * Increase oxygen production under the premise of ensuring oxygen purity; * Control the lower column oxygen-rich liquid empty 36 ~ 38% (liquid nitrogen restricts into the upper column valve V2); * Reduce the expansion amount under the premise of ensuring the main cold liquid level.   Liquid in coarse argon column   * On the premise of further precooling until the temperature of the argon tower no longer drops (the blowout and discharge valves have been closed), the liquid air is slightly opened (intermittently) and flows into the condensing evaporator valve V3 of the crude argon tower I to make the condenser of the crude argon tower intermittently work to produce backflow liquid, cool the packing of the crude argon tower I thoroughly and accumulate in the bottom part of the tower; Tip: When opening the V3 valve for the first time, pay close attention to the pressure change of PI-701 and do not fluctuate violently (≤ 60kPa); Obact the liquid level LIC-701 at the bottom of crude argon tower I from scratch. Once it rises to 1500mm ~ full scale range, stop precooling and close V3 valve.   Precooling argon pump   * Stop valve before opening the pump; * Blow out the valve V741 and V742 before opening the pump; * slightly open (intermittently) the pump after blowing off valve V737, V738 until the liquid is continuously ejected. Tip: This work is carried out under the guidance of argon pump supplier for the first time. Safety issues to prevent frostbite.   Start the argon pump   * Fully open the return valve after the pump, fully close the stop valve after the pump; * Start argon pump and fully open the back stop valve of argon pump; * Observe that the pump pressure should be stabilized at 0.5 ~ 0.7Mpa(G).   Crude argon column   (1) After starting the argon pump and before opening the V3 valve, the liquid level of LIX-701 will decrease continuously due to the liquid loss. After starting the argon pump, the V3 valve should be opened as soon as possible to make the condenser of the argon tower work and produce backflow liquid. (2) V3 valve opening must be very slow, otherwise the main tower conditions will produce large fluctuations, affecting the purity of oxygen, crude argon tower after work to open the argon pump delivery valve (opening depends on the pump pressure), the final delivery valve and return valve to stabilize the FIC-701 liquid level; (3) The resistance of two crude argon columns is observed. The resistance of
2019-06-10
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