On the causes of agglomeration of nano materials and the methods to prevent agglomeration

In recent years, a major development in science is nanotechnology, and many disciplines are scrambling to study nanotechnology At present, nano particles are widely used in civil and industrial fields, because nano particles can make materials change strangely and have properties that materials did not have before, and their attractive characteristics are shown in mechanical, structural, catalytic and physicochemical properties However, the application and preparation of nano particles also face a big problem, that is, the agglomeration of nano particles Specifically, for nano polycrystalline materials, agglomeration will lead to abnormal growth of particles, resulting in performance degradation; for nano materials with self-assembled structure, agglomeration will change the structure; for various fields directly using nano particles In addition, agglomeration directly affects the efficiency and properties of materials It can be seen that the key reason for the continuous improvement and progress of nanotechnology is the agglomeration of nanoparticles in nanomaterials In this paper, the causes of agglomeration of nanomaterials and the methods to prevent agglomeration are briefly introduced, especially the mechanical method, and the ultrasonic nano material emulsifying and dispersing device of Manelli is recommended Nanomaterials refer to materials that have at least one dimension in three-dimensional space in the nano scale range or are composed of them as basic units Nano materials have quantum size effect, small size effect, surface effect and macroscopical quantum tunneling effect because of the size of particles entering the nano scale, and show many unique properties, especially chemical activity It has wide application prospects in catalysis, filter, light absorption, medicine, magnetic medium and new materials However, the basic unit of nano materials, nano powder materials, are easy to agglomerate because of their unique activities, which brings inconvenience to the preparation, storage, transportation, use and many other aspects of nano materials There are many reasons for the agglomeration of nanoparticles, which are summarized as follows: 1 After the particles are refined to nanometer level, a large number of positive and negative charges accumulate on their surface area, and the agglomeration of surface charges causes the agglomeration of nanoparticles 2 Nanoparticles have large surface area, high surface energy, and are in an unstable state of energy, which is easy to aggregate to a stable state 3 The distance between nanoparticles is very short, and the van der Waals force between nanoparticles is far greater than their own gravity, so nanoparticles tend to attract each other and agglomerate 4 The interaction of hydrogen and chemical bonds between nanoparticles leads to the aggregation of nanoparticles 5 The quantum tunneling effect, charge transfer and the coupling of interface atoms among particles make particles reunite through the interface In order to solve the dispersion of nanoparticles, it is necessary to enhance the repulsion energy between nanoparticles Generally, the following three measures can be taken: 1 Strengthen the wettability of the surface of nanoparticles to the dispersing medium, change its interface structure, improve the strength and thickness of the solvated film, and enhance the repulsion of solvation; 2 Increase the potential absolute value of the double electric layer on the surface of nanoparticles, enhance the electrostatic repulsion between nanoparticles; 3, strengthen the three-dimensional protection through the adsorption of polymer dispersant on the surface of nanoparticles There are many measures to solve the agglomeration of nanoparticles, which can be divided into different types according to different basis According to the principle of dispersion, it can be divided into physical principle method and chemical principle method 1、 The physical principle method mainly introduces the mechanical force method here The mechanical force method is to use the rotation or vibration of the ball mill to make the hard enemies have strong impact, extrusion, impact, shear and friction on the raw materials when the dispersant is added The raw materials and the dispersant infiltrate and diffuse each other, so that the dispersant can be successfully coated on the surface of the nanoparticles The dispersant can form a layer of molecular film on the surface of particles, hinder the contact between particles, increase the distance between particles, avoid the formation of bridging hydroxyl group and real chemical bond, and also play a role of space resistance, so as to effectively prevent the agglomeration of nanoparticles The specific forms of mechanical force dispersion include grinding dispersion, colloidal grinding dispersion, ball milling dispersion, sand grinding dispersion, high-speed stirring, etc The advantages of mechanical force method are high yield, simple process and easy control In a short time, the dispersant can complete the coating of nano powder, and the anti agglomeration effect is good In addition, there are some physical principles and methods in the process of adding anti flocculant, water treatment, ultrasonic dispersion and storage 2、 Chemical principle method using chemical principle to prevent the agglomeration of nanoparticles is mainly to modify the surface of nanoparticles Surface modification is the most important way to solve the agglomeration of nanoparticles The surface modification is mainly to improve the surface chemical properties of particles, improve the dispersion of particles in the medium, reduce the degree of agglomeration, at the same time, give new properties to the material The surface chemical coating method has achieved good results in the surface modification of fluorescent materials and magnetic materials In this method, the surface properties of the powder are changed by changing the interfacial tension between gas-liquid and solid-liquid in the powder dispersion system and forming a certain thickness of adsorption layer or single-layer film on the powder surface At the same time, this method can reduce the surface energy of the particles, separate the nanoparticles from each other, achieve the dispersion effect, and improve the activity and durability of the particles Specifically: surface grafting reaction, coupling agent method, esterification reaction, vapor deposition method, etc Although physical dispersion and chemical dispersion are widely used in the preparation and use of nanoparticles, and have achieved good results, they also show some limitations Ultrasonic dispersion is a new dispersion method, which is simple in operation, good in quality, fast in speed and pollution-free The key of ultrasonic dispersing nanomaterials is cavitation effect When the liquid is affected by ultrasonic, a large number of microbubbles are produced in the liquid medium During the formation and fracture of microbubbles, energy is released Acoustic dispersion is an effective way to reduce the agglomeration of nanoparticles, but the use of superheated ultrasonic agitation should be avoided, because with the increase of thermal phase machinery, the probability of particle collision also increases, which leads to further agglomeration It is recommended that the ultrasonic emulsifying and dispersing system of nano material emulsifying and dispersing device with Manelli ultrasonic is to utilize the multiple cross reactions of ultrasonic such as dispersion, comminution and activation, which can destroy the solvent structure, improve the reaction activity, disperse the powder particles, and further reduce the linearity It has been proved by field experiments that the ultrasonic reactor can play a significant role in the ultrafine powder and nano dispersion of powder in liquid phase, and accelerate the reaction of powder, emulsion reaction and homogeneous reaction, which is widely used in chemical industry, petroleum, metallurgy, coal, electronics, medicine, building materials, light industry and other laboratory fields ★ main features: ● the concentrated ultrasonic material emulsifier is to directly immerse the horn of the high-power ultrasonic transducer into the reaction liquid, so that the sound energy can directly enter the reaction system without passing through the reactor wall of the cleaning tank Its advantage is that it can transfer a large amount of energy directly to the reaction medium, effectively convert electrical energy into mechanical energy, and control the ultrasonic energy by changing the amplitude of the energy delivered to the transducer (1) It can be equipped with cooling water circulating device, cooling water circulating device and special double-layer glass reaction kettle to form cooling water circulating system, which can realize accurate temperature control at any temperature point within the range of - 50 ~ 300 ℃, effectively avoiding tissue damage caused by high temperature, which is more convenient and accurate than traditional ice bath cooling (2) Magnetic stirrer is optional The emulsification rate of the treated sample can be improved by stirring, and the treatment effect is better ★ Product Description: ultrasonic emulsification and dispersion system is to directly immerse the horn of high-power ultrasonic transducer into the reaction liquid, so that the sound energy can directly enter the reaction system, without having to pass through the reactor wall of the cleaning tank Its advantage is that it can transfer a large amount of energy directly to the reaction medium, effectively convert electrical energy into mechanical energy, and can control the size of ultrasonic energy by changing the amplitude transmitted to the transducer ★ scope of use: emulsification and microemulsion of oil and water or other materials in the process of petroleum and chemical industry It can also be used for liquid treatment in light industry, nano materials, food and medicine sectors.