Welcome the spring of carbon nanotube industrialization
From:First Element   Date:2020-05-07   Hits:212

A tubular structure made of highly graphitized carbon atoms—carbon nanotubes. The configuration was proposed in the 1950s, and it was discovered and patented in the coke of ethylene cracking furnace in the 1970s, but its atomic structure was not until 1991. It was clearly revealed and defined by high-resolution electron microscopy technology. Scientists have thus realized that it has super high strength, toughness and excellent electrical and optical properties, which has become a research hotspot in academia. In the past 30 years, comprehensive research and research on the intrinsic structure, physical and chemical properties, control and mass preparation, and commercial application of carbon nanotubes have been conducted internationally. Not only has its macro-mechanical strength surpassed more than ten times that of the currently known good carbon fibers, it has produced and developed all-carbon nanotube 16-bit computer chips, small and fast switching X-ray tubes, etc. The progress of the industrialization of carbon nanotubes is also developing rapidly. Tiannai Technology Co., Ltd. has realized the production capacity of thousands of tons of multi-walled carbon nanotubes by fluidized bed method, and companies such as ZEON, OCSiAL and Beifang Guoneng have realized the production of tons of single-walled carbon nanotubes. Control capacity. Recently, LG company also announced a 1,700-ton/year multi-walled carbon nanotube production line. The application of carbon nanotubes has achieved considerable development and progress in many aspects, from the industrialization of conductive polymer materials, battery materials, super materials to electronic chip materials. Obviously, the development process of carbon nanotubes is a typical crystallization of the interaction between industry and academia. According to incomplete statistics, there are more than one hundred carbon nanotube manufacturers in the world, with a production capacity of over 10,000 tons per year. Let us see the spring of the development of carbon nanotube industrialization in this unusual spring of 2020.

  

(The picture comes from the Internet)

1. Fluidized bed-chemical vapor deposition technology has become the mainstream macro-preparation technology, providing a material basis for commercial applications.

Through more than 30 years of in-depth research, people realized that template autocatalysis with hydrocarbons and transition metals as the core is an efficient way to grow carbon nanotubes, and its large-scale production depends on the progress of chemical technology. Using hydrocarbons as raw materials, using gas-solid fluidized bed reactor technology with excellent heat and mass transfer performance and engineering scale-up methods, Tsinghua University achieved batch production of carbon nanotubes twenty years ago. The advancement of batch production technology has made the price of multi-walled carbon nanotubes, from US$60 per gram 20 years ago, is now lower than some high-end activated carbons, and its cost has dropped by nearly three orders of magnitude, successfully connecting with the market. High-quality and inexpensive carbon nanotubes provide a material basis for various performance studies and significantly promote the commercial application process. The demand of the macro application market has played a significant role in forming a single production line with a production scale of over 1,000 tons per year.


2. The development of new electrochemical energy sources at home and abroad has provided a stage for the commercial application of carbon nanotubes.

The high conductivity, small diameter and large aspect ratio of carbon nanotubes are very suitable for constructing a lightweight and excellent conductive network without hindering ion transmission. With this excellent performance, carbon nanotubes, as a conductive agent for lithium-ion battery materials, have been added and applied at the beginning of the birth of lithium-ion batteries. In recent years, it has gradually replaced traditional conductive agents such as conductive carbon black and carbon nanofibers, and has been widely used by lithium-ion battery companies. Due to the huge aspect ratio of carbon nanotubes, excellent performance can be achieved in a very small addition amount. Therefore, not only the internal resistance of the battery is reduced, and the cycle life of the battery is improved, but also more positive electrode materials can be added, which indirectly improves The energy density of the battery.

It is worth pointing out that since 2007, as a representative of new electrochemical energy, lithium-ion batteries can be used not only as batteries for mobile electronic devices such as mobile phones and computers, but also as the main power source of pure electric vehicles and the start and stop of hybrid vehicles. power supply. These important and huge application fields, such as communications and transportation, are the main markets for new international and domestic electrochemical energy storage equipment, and they have become the national strategy of many countries. At the same time, many countries have successively proposed a timetable for the ban on traditional fuel vehicles, which has also boosted the application of carbon nanotubes in the field of power batteries, occupying an important market share.

Specifically, the market demand for long-distance cruising of new energy vehicles poses a huge challenge to the energy density of power-type lithium-ion batteries. The current technical route with more industrialized competitive advantages is "high nickel ternary anode + silicon-based anode". Carbon nanotube conductive agent will play an irreplaceable role in improving the conductivity of high nickel ternary anode and silicon-based anode materials, and will further accelerate the replacement of other traditional conductive agents in the market. According to statistics, the output of ternary power lithium-ion batteries in 2018 increased by 118% year-on-year to 41.6GWh. In the ternary power lithium-ion battery, carbon nanotube conductive paste is mainly used, which increased the market size of carbon nanotube conductive paste by 30.1% year-on-year in the same year. It is estimated that by 2023, the global market output value of carbon nanotube conductive paste for power-type lithium-ion batteries will exceed 2.4 billion yuan, with a five-year compound annual growth rate of 40.3%. The growth mainly comes from the Chinese market and the acceleration of the introduction of carbon nanotube conductive pastes by Japanese and Korean companies. It is predicted from the technology development roadmap that the market scale of power-type lithium-ion batteries will continue to maintain a trend of rapid growth in the next few years, and will continue to drive the market application of carbon nanotubes.

In addition, grid-side energy storage has become an important development strategy for the United States, China, Australia and other countries, and lithium-ion batteries are still energy storage systems with large installed capacity. The annual installed capacity of lithium-ion battery energy storage systems in the United States and China both exceed the GW level. In this large-scale energy storage system (single system exceeding MW), more attention is paid to safety and long life. Carbon nanotube conductive agent can effectively reduce the internal resistance and heat generation of the battery, which is more advantageous than other conductive agents. This will further stimulate the blowout of the carbon nanotube market.


3. The field of composite materials is the key to exploring the application market of carbon nanotubes, with huge potential.

(1) Conductive plastic field

As an antistatic and electromagnetic shielding material, conductive plastic has become a popular material developed at home and abroad, and the application of static electricity protection and electromagnetic radiation protection materials is gradually increasing. Carbon-based filled conductive plastics have formed industrialized production and the market is mature by virtue of their high cost performance and adjustable resistance. The international mainstream manufacturers of carbon-based filled conductive plastics are concentrated in the United States, Europe and other places. Related products in my country still have a big gap with foreign products in terms of variety and quality stability. In terms of semi-conducting shielding materials for high cables and products related to integrated circuits, the degree of localization is low.

In the application of filled conductive plastics, carbon nanotubes have obvious advantages over traditional fillers such as carbon black in terms of electrical conductivity and mechanical properties, and their application ratio has gradually increased in recent years. With the expansion of the production scale and cost reduction of carbon nanotubes, as well as the gradual maturity of carbon nanotube dispersion technology, breaking through the technical barriers, it will significantly benefit the application of carbon nanotubes in the field of conductive plastics.

(2) Field of metal matrix composite materials

Metal materials are a wide range of structural strength materials with a wide range of applications. However, traditional metal materials have low specific strength and cannot effectively meet the needs of ultra-lightweight, ultra-strong and ultra-tough applications. Carbon nanotubes have a huge aspect ratio and excellent mechanical, electrical, optical and thermal properties. The use of carbon nanotubes as reinforcements to build metal matrix composites has the advantages of lightweight, high strength, high toughness, corrosion resistance and high temperature resistance, and has become a hot spot in the fields of new materials such as aerospace, defense, and automobiles.


4. The new field of 5G, the new battlefield of high-end carbon nanotubes, will be the commanding heights of international high-end technology competition in the future.

(1) In the field of chip manufacturing, the application of high-end carbon nanotubes as substrates has achieved technological breakthroughs.

Nano Access Memory (NRAM), as a new type of non-volatile memory based on carbon nanotubes for information storage. It mainly uses the excellent and discrete conductivity of carbon nanotubes to replace traditional field emission transistors (FET) based on semiconductor materials, and according to the identification of carbon nanotube arrays, under different microscopic forces (electrostatic or van der Waals adsorption) Two resistance states (0 or 1) to achieve the function of storing data.

The excellent mechanical and electrical properties of carbon nanotubes enable NRAM to have strong durability and thermal stability, as well as high speed and low power consumption. Specifically, NRAM has the following performance advantages: First, because carbon nanotubes have excellent chemical stability, it can ensure that NRAM can work normally under extreme environments such as high temperature, extreme cold, radiation, and vibration. Effectively expand the use boundary of the memory and significantly increase its service life. Secondly, under the premise that the read speed is as fast as DRAM (that is, dynamic random access memory, the most common system memory at present), the power consumption of NRAM is lower, and the power consumption in standby mode is basically zero. Furthermore, the excellent mechanical properties of carbon nanotubes make the NRAM carbon nanotube electromechanical switch have good repeatability, and it is expected to have unlimited (more than 1011 times) access endurance. Finally, the manufacture of NRAM only needs a layer of carbon nanotube coating (for data storage), which is much simpler than the preparation process of traditional multi-layer coatings for memory, so the cost is lower.

(2) In the field of flexible electronic devices, carbon nanotubes have moved towards industrialization.

For more "high-end" applications such as electronic devices and sensors, higher requirements are put forward for the purity, order, density, conductivity, and even chirality of carbon nanotubes. For example, IBM has set the purity standard for semiconductor-type single-walled carbon nanotubes used in transistors to be higher than 99.9999%, and the density should reach 125 pieces/μm.

Carbon nanotube flexible electronic devices have better performance than traditional transparent thin film semiconductors. For example, the transparent conductive film based on the super-aligned carbon nanotube array developed by the Tsinghua-Foxconn Nanotechnology Research Center has realized the industrialization of mobile phone touch screens through Tianjin Funa Yuanchuang Technology Co., Ltd., and successfully matched Huawei, Coolpad, ZTE and other mobile phones. The Finnish Canatu company is using the technology of the Kauppinen research group of the University of Aalto to promote applications such as a 3D touch screen with single-walled carbon nanotubes that can be stretched and deformed.


5. The safety of carbon nanotubes, related international and national standards and intellectual property protection issues

(1) The safety of carbon nanotubes

As a new man-made material with a very small diameter, carbon nanotubes can be used in two types: powder or composite. The safety of carbon nanotubes (such as absorption through the skin or inhalation) is an important issue. However, due to many types of carbon nanotubes, large differences in diameter and length, chemical stability, and different dispersion states, the current scientists have different conclusions on the toxicity analysis of carbon nanotubes, and they have not yet given a clear comprehensive picture. The conclusion. In general, materials in powder state need more attention to protection. It is necessary to standardize management and establish related systems to reduce the contact between employees and carbon nanotube powder in the production process. For example, the German Bayer company proposed that the upper limit of occupational exposure of carbon nanotubes is 50 mg/m3. According to the results of animal experiments, the National Institute of Occupational Safety and Health of the United States recommends that the occupational exposure limit of carbon nanotubes is 7μg/m3. In addition, the chemical stability of carbon nanotubes has also become a focus of research on environmental degradation. Scientists are carrying out research on the life cycle analysis of carbon nanotubes, which is expected to demonstrate the impact of carbon nanotubes on human society from a larger time and space scale, and to prevent the negative effects of new materials on human life. Generally speaking, the chemical degradability of carbon nanotubes should be better than graphite and carbon fiber materials, and relevant management regulations can be used for reference.

(2) International and national standards related to carbon nanotubes

With the continuous advancement of carbon nanotubes in commercial applications, international and national standards related to carbon nanotubes have been formulated and promulgated one after another.

Among them, the national standard of "Multi-walled carbon nanotubes" (GB/T 24491-2009) and the national standard of "Methods for testing the purity of multi-walled carbon nanotubes" (GB/T 24490- 2009), stipulating the terms and definitions, classification, technical requirements, test methods, inspection rules, packaging, marking and quality certificates, storage and transportation, safety precautions, etc., and purity methods and instruments for measuring multi-walled carbon nanotubes , Analysis steps and results presentation method.

The national standard of "Carbon Nanotube Conductive Paste" (GB/T 33818-2017), released and implemented in 2017, specifies the terms, requirements, testing methods, testing rules, signs, packaging, and transportation of carbon nanotube conductive pastes. , Storage and order form content. It is suitable for quality inspection and acceptance of liquid-phase series products that use multi-walled carbon nanotubes as conductive media in the fields of lithium-ion batteries, conductive coatings and conductive adhesives.

The International Standard for Carbon Nanotube Conductive Paste (ISO/TS 19808), which was implemented in 2020, led by Tina Technology as a representative of China, explains the characteristics of multi-walled carbon nanotube paste and the corresponding measurement methods.

These standardization efforts will contribute to the development of independent commercialization, compatibility, interoperability, safety and renewability of carbon nanotubes.

(3) Intellectual property protection in the carbon nanotube industry The acceleration of the industrial application of carbon nanotubes has made the protection of intellectual property rights in this field more important. In fact, due to the advance layout of Hyperion's patents in the field of conductive plastics, which hindered the research and development of large international companies in many fields, carbon nanotubes have only been used in a few occasions such as camera sleeves for a long time. In recent years, companies that have applied for more patents in the field of carbon nanotubes are concentrated in Japan, South Korea and China. The further expansion of the market in this field will drive the continuous evolution of the company's patent landscape as the patentee, and become a driving force for the change of this emerging material and nanotechnology. Paying attention to the protection of intellectual property rights in this field will help the sound and healthy development of new industries.

In short, carbon nanotubes have gradually achieved commercialization in these fields, and will occupy the online iterative market advantage in competition with other materials. As the earliest and widely used carbon material, carbon black has a history of more than two thousand years and has reached a usage rate of 10 million tons per year. It is expected that in the next thirty years, the share of carbon nanotubes in the lithium-ion battery market will continue to increase, reaching 100,000 tons/year. The application of high-strength, high-conductivity, and anti-static shielding materials may stimulate the production capacity of millions of tons and the actual composite material application market of tens of millions of tons. It will have a wide range of influence in the fields of super materials, functional composite materials and chips and optoelectronic materials. In the future, carbon nanotube products will have huge profit margins in the field of chip manufacturing. We have reason to believe that the spring of carbon nanotube applications has arrived.


Reference material:

1. Ji Zhonghai, Zhang Lili, Tang Daiming, Liu Chang, Cheng Huiming. Acta Metall Sinica (Chinese Edition), 2018, 54(11): 1665-1682.
2. Zhang Qiang, Huang Jiaqi, Zhao Mengqiang, Qian Weizhong, Wei Fei. Science in China: Chemistry, 2013, 43(6): 641 ~ 666.
3. Jiangsu Tiannai Technology Co., Ltd. initial public offering and listing prospectus on the Science and Technology Innovation Board, 2019.
4. The national standard of "Multi-walled Carbon Nanotubes" (GB/T 24491-2009).
5. The national standard of "Methods for Testing the Purity of Multi-walled Carbon Nanotubes" (GB/T 24490-2009).
6. National standard of "Carbon Nanotube Conductive Paste" (GB/T 33818-2017).
7. Nanotechnologies — Carbon nanotube suspensions — Specification of characteristics and measurement methods (ISO/TS 19808).