The carbon nanotube touch screen was successfully developed for the first time in 2007~2008, and was industrialized by Tianjin Fu Na Yuanchuang Company on 20 1 1. So far, many smart phones use touch screens made of carbon nanotubes. Different from the existing indium tin oxide (ITO) touch screen, indium tin oxide contains rare metal "indium", and the raw materials of carbon nanotube touch screen are hydrocarbon gases such as methane, ethylene and acetylene, which are not limited by rare mineral resources; Secondly, the carbon nanotube film made by the spread film method has conductive anisotropy, just like the natural built-in graphics, which does not need the processes of lithography, etching and water washing, saving a lot of water and electricity, and is more environmentally friendly and energy-saving. Engineers have also developed a positioning technology using the conductive anisotropy of carbon nanotubes, which only needs a layer of carbon nanotube film to judge the X and Y coordinates of the touch point. The carbon nanotube touch screen also has the characteristics of flexibility, anti-interference, waterproof, anti-collision and anti-scratch, and can be made into a curved touch screen, which has great potential for applications in wearable devices, intelligent furniture and other products.
According to the report of Physicist Organization Network and BBC on September 26th, 20 13, engineers of Stanford University in the United States made a breakthrough in the field of new generation electronic equipment, and built a computer prototype with carbon nanotubes for the first time, which is smaller, faster and more energy-saving than the computer based on silicon chip mode.
Professor Giovanni de mikkeli, director of the School of Electrical Engineering of the Federal Institute of Technology in Lausanne, Switzerland, emphasized two key technical contributions of this worldwide achievement: First, the manufacturing process based on carbon nanotube circuits is in place. Secondly, a simple and effective circuit is established, which shows that it is feasible to use carbon nanotubes for calculation. Professor naresh from the Next Generation Chip Design and Research Alliance and the University of Illinois at Urbana-Champaign commented that although it may take several years for carbon nanotube computers to mature, this breakthrough highlights the possibility of industrialized production of carbon nanotube semiconductors in the future.
Hydrogen is regarded by many as a clean energy source in the future. However, the density of hydrogen itself is low, so it is very inconvenient to compress it into liquid for storage. Carbon nanotubes are light in weight and hollow in structure, which can be used as excellent containers for storing hydrogen, and the density of hydrogen stored is even higher than that of liquid or solid hydrogen. With proper heating, hydrogen can be released slowly. Researchers are trying to make portable hydrogen storage containers with carbon nanotubes.
Carbon nanotubes can be filled with metals, oxides and other substances, so that carbon nanotubes can be used as molds. First, carbon nanotubes are filled with metals and other substances, and then the carbon layer is etched away, so that the thinnest nano-scale wires or brand-new one-dimensional materials can be prepared and applied to future molecular electronic devices or nano-electronic devices. Some carbon nanotubes themselves can also be used as nano-scale wires. In this way, microfilaments made of carbon nanotubes or related technologies can be placed on silicon wafers to produce more complex circuits.
Many excellent composite materials can be made by using the characteristics of carbon nanotubes. For example, plastics reinforced with carbon nanotubes have excellent mechanical properties, good electrical conductivity, corrosion resistance and shielding radio waves. Carbon nanotube composites based on cement have good impact resistance, antistatic property, wear resistance and high stability, and are not easy to affect the environment. Carbon nanotube reinforced ceramic composites have high strength and good impact resistance. Due to the existence of five-membered ring defects on carbon nanotubes, the reaction activity is enhanced. Under the conditions of high temperature and other substances, carbon nanotubes are easy to form tubes at the end opening, and are easy to be infiltrated by metals to form metal-based composites with metals. This material has high strength, high modulus, high temperature resistance, small thermal expansion coefficient and strong thermal deformation resistance.
Carbon nanotubes also provide physicists with the best capillary tube to study the mechanism of capillary phenomenon and chemists with the best test tube for nano-chemical reaction. The tiny particles on carbon nanotubes can cause the swing frequency of carbon nanotubes to change in the current. Taking advantage of this, in 1999, scientists in Brazil and the United States invented a "nano-scale" with an accuracy of 10- 17kg, which can weigh the mass of a single virus. Then German scientists developed a "nano-scale" that can weigh a single atom.
Introduction and suggestion on the use of carbon nanotube dispersant
Taking carbon nanotubes and carbon nanotube dispersants of Wuxi Wang Ju Plastic Materials Co., Ltd. as examples, the research and practical experience are as follows:
First, the three elements of carbon nanotube dispersion technology
Second, the recommended dosage of dispersant
Three. Overview of carbon nanotube water dispersant
Four. Suggestions on the use of ultrasonic dispersion equipment and examples of dispersion
Verb (abbreviation of verb) Suggestions on the use of grinding and dispersing equipment
Three elements of carbon nanotube dispersion technology: dispersion medium, dispersant and dispersion equipment
1, dispersion medium
(1) According to different viscosities, dispersion media can be divided into three types: high viscosity, medium viscosity and low viscosity. Carbon nanotubes are easy to disperse in low viscosity media such as water and organic solvents. Medium viscosity media such as liquid epoxy resin and liquid silicone rubber. High viscosity media, such as molten plastic.
(2) The dispersion technology of carbon nanotubes introduced here is aimed at medium and low viscosity dispersion media.
2. Dispersant
The choice of (1) dispersant is closely related to the structure, polarity and solubility parameters of the dispersion medium.
(2) The dosage of dispersant is related to the specific surface area of carbon nanotubes and the functional groups modified by valence bonds.
(3) TNWDIS is recommended as an aqueous medium. In strong polar organic solvents, such as alcohol, DMF and NMP, TNADIS is recommended. It is suggested to use moderate polar organic solvents such as esters, liquid epoxy resin and liquid silicone rubber.
3. Decentralized equipment
(1) ultrasonic dispersion equipment: it is very suitable for dispersing carbon nanotubes in laboratory scale and low viscosity media, but it will be limited when used in medium and high viscosity media.
(2) Grinding and dispersing equipment: suitable for large-scale dispersion of carbon nanotubes and medium viscosity dispersion of carbon nanotubes.
(3) The combined method of "grinding and dispersing first, then ultrasonic dispersing" can disperse carbon nanotubes efficiently and stably.
Recommended dosage of dispersant.
1, specific surface area of carbon nanotubes and amount of dispersant.
Our reagent grade carbon nanotubes are divided into single-walled tubes (outer diameter
The recommended dosage of TNWDIS: 3.5 times of the weight of single-walled pipe, 0 times of TNM 1 weight, 0.2 times of TNM8 weight. Reference adjustment of residual dose
2. Functionalization of carbon nanotubes and dosage of dispersant
Functionalized carbon nanotubes are more easily dispersed in water. Generally, after carboxylation of carbon nanotubes, the amount of dispersant can be reduced by 50%.
Recommended dosage of TNWDIS: 1.5- 1.8 times the weight of carboxylated single-walled pipe, 0.5 times the weight of carboxylated TNM 1 weight, and 0. 1 times the weight of carboxylated TNM8.
3. For TNADIS, the recommended dose of TNM8 is 0.2 times of body weight. For TNEDIS, the recommended dose of TNM8 is 0.8 times of body weight.
The dosage of other carbon nanotube dispersants can be adjusted by reference.
Overview of carbon nanotube water dispersant
1, a nonionic surfactant without alkylphenol polyoxyethylene ether (APEO), is environmentally friendly. Since 1976, European countries have formulated laws and regulations to restrict the production and use of APEO.
2. Containing aromatic groups, it is especially suitable for preparing aqueous dispersion of carbon nanotubes. Aromatic groups have good affinity with the wall of carbon nanotubes and are easily adsorbed on the wall.
3. Performance indicators
Active substance content: 90%
Water content: 10%
Cloud point: 68-70℃
Structure of carbon nanotube water dispersant
Three kinds of surfactants commonly used to disperse carbon nanotubes are reported in the literature.
Suggestions on using ultrasonic dispersion equipment
1, ultrasonic pulverizer (tip type) and ultrasonic cleaner (bath type) can all be used to disperse carbon nanotubes.
2. The ultrasonic wave emitted by the ultrasonic pulverizer has high energy density (energy is concentrated on the horn instead of a plane) and low frequency, which is more suitable for the dispersion of carbon nanotubes. According to the amount of carbon nanotube dispersion, the appropriate power of ultrasonic pulverizer and the diameter of horn are selected.
3. In water medium, the cavitation of ultrasonic wave will make TNWDIS produce a small amount of foam, which will affect the ultrasonic effect. You can choose to stand still or add defoamer to eliminate foam.
The medium with high viscosity is not suitable for ultrasonic equipment dispersion, so it is recommended to choose grinding and dispersion equipment.
Examples of preparing dispersion by ultrasonic pulverizer
1. Objective: To prepare 100g aqueous dispersion of multi-walled carbon nanotubes (TNM8) with a carbon nanotube content of 2%.
2. Main equipment
(1) scientiz-Ⅱ d ultrasonic cell pulverizer (made in China). The ultrasonic horn used is φ 6, the output power is 60%, the ultrasonic on time is 3s, the ultrasonic off time is 3s, and the total ultrasonic time is 5min.
(2)SC-36 14 low-speed centrifuge (made in China)
(3)HCT- 1 Microcomputer Differential Thermal Balance (made in China)
Operating steps (1)
1. 0.40 g of dispersant TNWDIS was dissolved in 97.60 g of deionized water. TNWDIS has low solubility at room temperature, and can be dissolved by water bath heating, but the use temperature should not exceed its cloud point temperature.
2. Add 2.00 grams of carbon nanotubes and stir them, so that the carbon nanotubes are completely wetted by the aqueous solution of dispersant instead of floating on the water.
3. Start the ultrasonic examination. In the process of ultrasound, the dispersion will generate heat and bubbles, so it is suggested that after 5 minutes of ultrasound, the dispersion can be taken out, cooled in ice water, defoamed, and then continue ultrasound.
4. Observation of dispersion. Dip a small amount of dispersion into clear water with a glass rod and observe the dilution state. Dispersed carbon nanotubes, like a drop of ink, fall into the water and disperse rapidly and evenly, while non-dispersed carbon nanotubes will have black particles in the water. The total ultrasound time is 30 minutes (5 minutes ×6 times).
5. After ultrasonic treatment, the dispersion is centrifugally settled to remove undistributed agglomerated particles. The centrifugal speed is 2000 rpm and the centrifugal time is 30 minutes. After centrifugation, the dispersion can remain stable for more than half a year.
6. After centrifugation, the upper liquid passes through a 300-mesh filter cloth to obtain the final carbon nanotube dispersion. Dry the lower sediment to constant weight, and record it as G2. The precipitation was analyzed by thermogravimetric analysis, and the thermal weight loss rate f(%) at 450℃ was defined as the content of dispersant in the precipitation.
7. The actual content of carbon nanotubes in the dispersion (%)=2.00-( 1-f)× G2.
Suggestions on the use of grinding and dispersing equipment
1. To prepare 1-2 liter aqueous dispersion of carbon nanotubes, a laboratory dispersion sand mill can be selected, and the grinding medium can be 1.0- 1.2 mm zirconium silicate beads or zirconia beads.
2. In order to prepare 10-20L dispersion of carbon nanotubes, a small basket sander can be selected. The grinding medium is zirconium silicate beads or zirconia beads with smaller diameter allowed by the equipment.
3. In the process of grinding water medium sand, defoamer should be added to reduce the influence of foam on dispersion effect.
4. For medium viscosity dispersion media, such as liquid epoxy resin, the sand mill can't effectively drive the media to move, so you can choose cone mill or three-roller mill for grinding and dispersion.