"Flashing" waste tires "changing" graphene in seconds

"Flashing" waste tires "change" graphene in seconds
??? Flashing heating process can quickly extract graphene from waste rubber tires .
■Reporter Qin Zhiwei Can waste rubber tires "flash" graphene? A kind of "point" The new technology of "Shichengjin" is expected to turn 800 million waste tires into "babies" every year
.
Recently, the team of Professor James M.
Tour from Rice University in the United States published a paper on "Carbon" saying that they use flash heating technology, Graphene can be quickly extracted from waste rubber tires and used to reinforce concrete
.
This process can instantly reach a high temperature above 3000 ℃ to achieve graphitization of carbon black, coal, coke, coffee, etc.

"The flash heating process is used to prepare graphene, It is a new way to reuse waste rubber
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However, whether this flash graphene can be truly applied in multiple fields still needs to be verified by the industry
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"Professor Gao Libo of the School of Physics of Nanjing University told the China Science News, "Once verified to be effective, the method can also be applied to other waste organic and macromolecules, and high carbon content materials
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"From graphitization to "flashing" "Ultra-high temperature environment turns high-carbon content materials into graphite" is not unfamiliar to those engaged in material preparation research, that is, the graphitization process
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"This process uses the'sp2 of carbon atoms' Chemical bond is the most stable principle of all chemical bonds in carbon materials
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"Gao Libo introduced to the China Science Daily that in high temperature environments, all carbon atoms tend to transform into graphite structures
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For example, under ordinary pressure, diamond materials will transform into graphite structures when the temperature is higher than 2500°C
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In fact, regardless of the principle.
Still in practice, Gao Libo has learned from the research field of carbon materials that waste tires and other materials can be turned into graphite structure
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But the only thing that is difficult to break through is how to achieve a high temperature environment, that is, a new preparation process
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As early as 2011, Tour led the team to try to use a variety of high-carbon content organics to prepare graphene using a traditional tube furnace with a furnace temperature of about 1000°C to 1200°C
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However, the graphene prepared by this method, although the crystal quality is good, but the yield is low, which cannot meet its application in structural materials
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Until 2020, the Tour team finally made a major breakthrough, developed a flash heating process, and published it in Nature
.
“The products after graphitization are mostly a few atomic layers, mostly within 5 layers, which can also be called graphene
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” Gao Libo said, “similar to the arc method used to prepare nano-carbon materials 30 years ago
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” The arc method electrode material is usually It is graphite, and pulse current is also applied to achieve the purpose of vaporizing part of the graphite electrode.
Generally, the temperature of the arc zone exceeds 3000 ℃
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With this method, fullerenes and carbon nanotubes can be effectively prepared in the early stage
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It is worth mentioning that, as the main developer of the new preparation process, Tour has conducted related research with Richard Smalley, one of the discoverers of fullerenes and Nobel Prize winner in Chemistry
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"It has also been reported that the arc method is used to prepare graphene, but the yield is lower
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" Gao Libo said that compared to the vacuum environment required by the arc method, the flash heating process simplifies the reaction environment, adopts a simpler atmospheric pressure environment, and uses copper as the electrode.
Electrode, the reaction material is placed in the center of the electrode
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This process is not difficult to understand
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"If you have used an iron, you will see the effect of Joule heating
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" Chen Chengmeng, a researcher at the Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, told the China Science Daily that when current passes through conductive materials such as iron metal, heat is quickly generated
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The researchers named the graphene obtained by this process flash graphene, and the stacked flash graphene exhibits a stack of turbine layers
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However, Gao Libo also emphasized that this process is not suitable for the preparation of chip-level high-quality graphene film samples..
Another way to turn waste into treasure The research results of the Tour team previously published in "Nature", the raw materials are mostly powder, which means that these raw materials are easy to place between the two electrodes, and the sparks generated between the electrodes can be effective Penetrate the powder to achieve the purpose of uniform heating
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The raw materials used in the research results released by "Carbon" are waste tires
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"Although waste tires have sufficient carbon content, they are lumpy, not easy to turn into powder, and electric sparks are not easy to penetrate tires
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" Gao Libo analyzed that for carbonized waste tires, the process optimized by the Tour team mainly extended the electric spark Pulse time
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For powder raw materials, the pulse time is generally in the millisecond level, while for waste tires, it is close to the second level
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Tour said that most of the 800 million tires discarded every year in the world are used as fuel or ground for other purposes, and 16% of the tires are landfilled
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"If it is used to produce graphene, millions of tires can be effectively used
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" As far as China is concerned, according to the statistics of the Ministry of Public Security, the number of motor vehicles in 2020 will reach 372 million, of which 281 million are cars
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With the rapid development of the automobile industry, more than 300 million waste tires are produced in China each year, and the equivalent weight has exceeded 10 million tons
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Problems such as environmental pollution, waste of resources, and potential safety hazards caused by waste tires have become more and more prominent
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Pan Jinsong, a senior engineer at Shandong Institute of Industry and Information Technology, introduced that the comprehensive utilization of waste tires includes old tire retreading, production of recycled rubber, production of rubber powder, and thermal cracking
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The study of graphene from used tires has also been reported before
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For example, in 2019, the research group of Professor Li Huiqiao of Huazhong University of Science and Technology and the research group of Professor Sun Qingfeng of Zhejiang Agriculture and Forestry University cooperated to use alkali-assisted carbonization to convert waste tires into 3D graphene.
The method used is to change the traditional alkali heat treatment temperature from Increase from 800°C to 1000°C
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"Using the flash heating process to prepare graphene is another way to reuse waste rubber tires
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" Gao Libo said
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However, when carbonizing waste tires, in order to extend the spark pulse time, major improvements are needed in terms of improvement of production equipment and safety upgrades
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The latest research results of the Tour team, "just report that if you want to graphitize rubber tires, you need a longer electric spark pulse time
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" Another issue that Chen Chengmeng pays attention to is the huge amount of waste tires every year, whether low-cost, high-yield, large-volume conversion can be achieved, and recycling can be achieved.
This is also a problem that laboratory technology must face when it comes to industrial applications
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The application prospects are promising, regardless of whether the raw material is coal or waste rubber tires, the graphene obtained by the flash heating process is a powder graphene with high graphite crystallinity
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"This kind of graphene can be close to intrinsic graphene in terms of heat conduction and electrical conductivity
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Its application and graphene obtained by chemical exfoliation methods have similar prospects
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" Gao Libo said
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He further explained that the current method of preparing graphene is the traditional production method.
It mainly targets energy storage and heat conduction.
The application is chemical exfoliation.
The graphene product exists in the form of powder; it targets future applications in the chip field.
Graphene is mainly grown by chemical vapor deposition, and silicon carbide epitaxy is also advancing at the same time
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Studies have confirmed that flash graphene has better electrical conductivity, thermal conductivity and mechanical enhancement effects, and the process is more environmentally friendly and low energy consumption
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"If the graphene prepared by this method has new quality characteristics and more suitable application scenarios, then graphene produced based on waste rubber tires will show great development potential
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" Chen Chengmeng told China Science Daily
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He roughly estimated to reporters that 1 kilowatt-hour of electricity = 1000W×3600S=3600 kilojoules, 1 kilowatt-hour of electricity can synthesize 500g of graphene, calculated at 0.
53 yuan for 1 kilowatt-hour of electricity, the electricity cost of 1 kilogram of graphene is as low as 1.
06 yuan.
Graphene may be cheaper than cabbage in the future
.
"Therefore, the cost of graphene obtained by this method is low enough to be compounded with plastics, metals, plywood, concrete and other building materials, and is widely used in composite materials
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" Chen Chengmeng said
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The latest paper also mentions that graphene converted from waste tires can be used to enhance the mechanical properties of concrete
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The world produces about 26 billion tons of concrete every year, and its carbon dioxide emissions account for about 9% of the total global emissions
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"If less concrete is used in roads, buildings and bridges, then some emissions can be eliminated from the beginning,
" Tour said
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Long before graphene, it has been reported that carbon fibers and carbon nanotubes can be added to concrete to increase toughness and enhance durability
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"The graphene obtained by the flash heating process can further increase the compressive resistance of concrete
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" Gao Libo also emphasized that the final effect may require more research or industrial standardization
.