The more practical and excellent characteristics of ultrafine powder
particles are mainly surface effect
and volume effect
As the particle size decreases, the ratio of area to volume increases, which is prone to agglomeration.
Therefore, it is necessary to treat the surface of the powder to make it in a dispersed state and give full play to its excellent properties.
The surface coating of the powder is to apply physical or chemical methods to the surface of the particles as needed. The surface of the particles is coated with inorganic or organic substances, and a coating layer is introduced on the surface of the particles.
In this way, the modified powder can be regarded as a composite powder composed of a "core layer" and a "shell layer".
1. What is the purpose of surface modification?
Coating a layer of different components on the surface of the powder can change its optical, magnetic, electrical, catalytic, hydrophilic, hydrophobic and sintering characteristics, and improve its corrosion resistance, durability, service life, and thermal, mechanical and thermal characteristics. Chemical stability, etc. To solve the problem of agglomeration of ultrafine powder and improve its dispersibility and rheology, the most effective method is to modify the surface of the powder. The scope of ultrafine powder modification:
2. What is the mechanism of surface modification?
The mechanism of surface modification of ultrafine powder is that the surface of ultrafine powder interacts with the surface modifier to improve the wettability of the particle surface, enhance the interfacial compatibility of the particle in the medium, and make the particle easy to be contained in organic compounds or Disperse in water. Coating modification is to cover the surface of particles with inorganic compounds or organic compounds, which can weaken or shield the agglomeration of particles. The steric hindrance repulsion is generated due to the coating, which makes it very difficult for particles to re-agglomerate. Sexual purpose.
3. What are the methods for surface modification of ultrafine powders?
(Process flow chart of surface coating modification of ultrafine powder)
4. What are the equipment for surface modification of superfine powder?
The powder surface modification equipment is mainly responsible for three responsibilities: one is mixing; the other is dispersion; the third is that the surface modifier is melted and uniformly dispersed on the surface of the material in the equipment, and produces a good combination. At present, the surface modifiers mainly include:
The development trend of surface modification equipment is: on the basis of equipment structure optimization, advanced computer technology and artificial intelligence technology are used to automatically adjust the main parameters and the amount of modifiers on-line to realize the monolayer adsorption of surface modification on the particle surface , Reduce the amount of modifier, stabilize product quality and facilitate operation.
5. What type of powder modifier?
The surface modification of the powder is mainly realized by the adsorption, reaction, coating or coating of the surface modifier on the surface of the powder particles. Therefore, the surface modifier has a decisive effect on the surface modification of the powder. The surface modifiers currently used mainly include coupling agents, surfactants, organic oligomers, unsaturated organic acids, silicones, water-soluble polymers, and metal oxides and alkoxides.
6. What are the factors that affect the effect of surface modification?
The main factors that affect the effect of powder surface modification are the nature of the powder raw materials, the formulation of surface modifiers, the surface modification process, and the surface modification equipment. The specific surface area, particle size, particle size distribution, specific surface energy, surface physical and chemical properties, agglomeration, etc. of the powder raw materials all have an impact on the surface modification effect; the formula of the surface modifier includes the selection of the variety, the determination of the dosage and the usage, etc. ; The surface modification process must meet the application requirements of surface modifiers, while requiring simple process, good parameter controllability, stable product quality, low energy consumption and low pollution; high-performance surface modifiers should be able to make powder And the dispersibility of the surface modifier is good, and the powder and the surface modifier have an equal chance of contact or action.
7. How to characterize the effect of surface modification of ultrafine powder?
There are direct evaluation methods and indirect evaluation methods to characterize and evaluate the surface modification effect of ultrafine powders. The direct evaluation method is to evaluate the modification effect by measuring the mechanical properties of the modified powder as a filler applied to the composite material and the processing performance in the material.