Nanoparticle materials
The form of nanoparticles used directly in application is called nanoparticle type material. The ultrafine particle catalyst called the fourth generation catalyst, using very high specific surface area and activity can significantly improve the catalytic efficiency, for example, the ultrafine particles of nickel and steel-zinc alloy with a particle size of less than 0.3 microns are The catalyst made of the main components can make the chlorination efficiency of organic matter up to 10 times that of traditional nickel catalysts; ultra-fine iron particles as a catalyst can decompose carbon dioxide into carbon and water at low temperature, and ultra-fine iron powder can be used in the thermal decomposition of benzene gas phase It acts as a nucleus to produce carbon fibers.
It is very important to study the specific surface area of ​​nano-particle materials. The detection data of specific surface area of ​​nano-particle materials is only reliable when the results are detected by the BET method. There are many instruments in China that can only be tested by direct comparison methods. It was also eliminated. At present, the multi-point BET method is used uniformly for the specific surface area testing at home and abroad. The specific surface area measurement standards developed at home and abroad are based on the BET test method. Please refer to China's national standard (GB / T 19587-2004)-Gas adsorption BET principle Method for determining the specific surface area of ​​solid materials. The measurement of specific surface area is actually a time-consuming task. Due to the different adsorption capacity of the sample, the test of some samples may take a whole day. If the test process is not fully automated, then the tester ca n’t leave at all times. A high degree of concentration, observing the instrument panel, manipulating the knob, and a little inattention will lead to the failure of the test process, which will waste a lot of precious time of the tester. The F-Sorb 2400 specific surface area analyzer of Beijing Jine Spectrum Technology Co., Ltd. is an instrument that can truly realize the detection function of the BET method (with direct comparison method), and the more important F-Sorb 2400 specific surface area of ​​Beijing Jin Ai Spectrum Technology Co., Ltd. The analyzer is the only fully automated intelligent specific surface area detection device in China so far. Its test results are highly consistent with international standards, and its stability is also very good. At the same time, it reduces human errors and improves the accuracy of test results.
Audio tapes, video tapes and magnetic disks all use magnetic particles as magnetic recording media. With the informatization of society, the requirement for large information storage capacity and high information processing speed is driving the increasing density of magnetic recording, and the size of magnetic particles used for magnetic recording tends to be ultra-miniaturized. At present, metal magnetic tapes and magnetic disks made of metal magnetic powder (supermicro magnetic particles of about 20 nanometers) have been commercialized abroad, and their recording density can reach 4′106 ～ 4′107 bits / cm (107 ～ 108 bits / inch) It can record 4 million to 40 million information units per centimeter. Compared with ordinary magnetic tape, it has the advantages of high density, low noise and high signal-to-noise ratio.
The ultra-fine silver powder and nickel powder light sintered bodies are used as electrodes in chemical batteries, fuel cells and photochemical batteries, which can increase the contact area with liquid or gas, increase the battery efficiency, and help to miniaturize the battery. The ultra-fine particles of light sintered body can produce microporous filters. For example, the micropore filter made of ultrafine nickel particles has an average pore size of up to 10 nanometers, which can be used for the separation and concentration of gas isotopes, mixed rare gases, organic compounds, and can also be used in fermentation, medicine and biotechnology. Magnetic ultrafine particles, as carriers of medicines, are concentrated at the patient's site under the guidance of an external magnetic field, which is conducive to improving the efficacy of medicine. Researches in this area are actively conducted at home and abroad. Ultrafine gold particles are used to make gold sols, and then indirect agglutination tests for immunology can be performed by connecting antigens or antibodies, which can be used for rapid diagnosis. If the gold sol pregnancy reagent is added to the urine of pregnant women, the color of non-pregnancy is colorless, and the pregnancy is significantly red. Only 0.5 grams of gold can be used to prepare 10,000 milliliters of gold sol, which can measure 10,000 times and the judgment result is clear reliable. There is an ultra-fine particle emulsion carrier, which is easy to be fused with cancer cells scattered in the human body. If it is used to wrap anti-cancer drugs, it is expected to be made into a cancer "missile".
Incorporating ultrafine metal particles such as copper and nickel in the manufacturing process of chemical fibers can synthesize conductive fibers to make fiber products or electrothermal fibers that are resistant to electromagnetic radiation, and can also form conductive composites with rubber and plastic.
In the Gulf War in the spring of 1991, the US F-117A stealth fighters carrying out air raid missions also contained a variety of ultrafine particles in the infrared and microwave stealth materials coated on the outer surface of their fuselages. Absorptive capacity. Adding 1% by weight of ultra-fine aluminum or nickel particles to the solid fuel propellant launched by the rocket can increase the heat of combustion per gram of fuel by a factor of 1. In addition, ultra-fine, high-purity ceramic ultra-fine particles are necessary materials for precision ceramics. Therefore, ultrafine particles are widely used in various fields of national defense and national economy.
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