[Introduction] Nanomaterials can be uniformly dispersed in the mixture by effective chemical and physical dispersion methods, which plays an important role in improving the performance of the refractory. Nanomaterials, such as breakthroughs in the dispersion of nanopowders, will be greatly developed. Nanotechnology has a very broad application prospect in the market of refractory materials.
The application of nanotechnology in refractory materials is mainly based on the application of nano-powders and sols. The nano-powder has high surface energy, high activity, and is extremely unstable. It is easily combined with other atoms, and its melting point and sintering temperature are much lower than that of micropowder. Nano-powders are mainly used in amorphous refractories and some special refractories. In the amorphous refractory material, the nano-powder is mainly introduced in the form of a binder and an additive, and the surface and interface effects of the nano-powder are used to reduce the amount of cement, thereby reducing the amount of water added and improving the mechanical properties of the castable. After the nano-powder is added into the special refractory material, the interface between the nano-powders has high energy, and the high interface in the sintering can be released as an additional driving force for sintering, which is beneficial to the shrinkage of the pores in the interface and the filling of the vacancies. Therefore, sintering at a lower temperature can achieve the purpose of densification, and the performance is excellent.
Nano refractory
(1) Silica sol-bonded castables, due to the high drying rate and high initial permeability, in some cases, the drying time of the silica sol-bonded castable is reduced by half or more than the cement-bonded castable. The requirement for a short operating cycle of the equipment.
(2) In terms of strength, although the cement has a higher initial strength, the strength of the cement-bonded castable will gradually decrease when the temperature is raised; the initial strength of the silica-sol-bonded material is lower, but its strength is As the temperature increases, the strength increases, and the strength of the cement-bonded castable at medium temperature can be reached in a short time.
(3) In the cement-bonded castable, the formation and volume instability of the glass phase results in a decrease in its thermal shock resistance. The silica sol-bonded castables have good volume stability and thermal shock resistance.
Dispersion method of nano powder - mechanical force dispersion
Mechanical force dispersion is mainly a method of sufficiently dispersing nanoparticles by mechanical force such as external shear force or impact force. In fact, this is a very complicated dispersion process. By applying mechanical force to the dispersion system to cause changes in the physical and chemical properties of the substances in the system and accompanying a series of chemical reactions, the dispersion can be achieved. The specific forms of mechanical force dispersion include grinding dispersion, colloid mill dispersion, ball mill dispersion, sanding dispersion, and high-speed stirring dispersion. Ball mill dispersion is currently the more common method, but in the ball milling process, the wear impurities generated by the impact of the ball easily enter the slurry, which has an impact on its performance. According to the literature, a high-speed mixer of 5000 rmin-1 or more is required by simply using mechanical stirring.
Chemical dispersion
Chemically modified dispersion is the use of surface groups of nanoparticles to chemically bond with reactive organic compounds. Nanoparticles have solubility in organic media due to the presence of organic compound branches or groups on the surface, thereby enhancing the nanoparticle in organic Dispersion in the medium. There are usually two ways to chemically modify: one is to chemically react a terminal group of a macromolecule with a surface group of a nanoparticle to graft the polymer onto the surface of the nanoparticle. The second is to use a polymerizable organic small molecule to polymerize on the active site of the surface of the nanoparticle to form a polymer layer on the surface of the nanoparticle. In addition, the dispersion of the nanoparticles is often carried out by combining physical dispersion and chemical dispersion. For example, in the ultrasonic dispersion process, adding an appropriate amount of the dispersant can significantly improve the dispersion effect. This is because only the cavitation of the ultrasonic waves is difficult to prevent re-agglomeration of the nanoparticles after sonication. After the addition of the dispersant, the particles can be prevented from agglomerating again, and at the same time, the ultrasonic effect is beneficial to the coating of the dispersant on the surface of the nanoparticles.
The development direction of nano powder dispersion technology
The dispersion behavior of nano-powders has some similarities with the micro-powders of the same composition. However, due to the high activity of the nanopowder, the surface morphology and adsorption properties have changed, and the dispersion of the nanopowder has its own characteristics.
Conclusion
At present, due to the application of nanotechnology in refractory materials, the technology and process are still not mature, and further exploration and improvement are needed. Nanomaterials can be uniformly dispersed in the mixture by effective chemical and physical dispersion methods, which plays an important role in improving the performance of the refractory. Nanomaterials, such as breakthroughs in the dispersion of nanopowders, will be greatly developed. Nanotechnology has a very broad application prospect in the market of refractory materials.
(Source: Looking for refractory nets)
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