Research progress on surface modification of ultrafine powder materials— Surface cladding modification

At present, there are many methods of surface modification, and the classification methods vary according to the angle of analyzing the problem. The powder surface modification methods are divided into 6 categories: surface coating modification, surface chemical modification, mechanical chemical modification, capsule modification, high-energy modification, and precipitation reaction modification.

Purpose of surface modification of ultrafine powder

1. To improve or change the dispersion of powder particles;

2. To improve durability, such as drug resistance, light resistance, heat resistance, weather resistance, etc.;

3. To improve particle surface activity;

4. To generate new physical, chemical and mechanical properties and new functions on the surface of the particle, thereby increasing the added value of the powder.

Surface Coating Modification: Principles and Applications in Particle Dispersion

Surface coating modification is that the surface modifier has no chemical reaction with the surface of particles, and the coating and particles are connected by physical methods or van der Waals forces. This method is almost suitable for the surface modification of all kinds of inorganic particles. This method mainly uses inorganic compounds or organic compounds to cover the particles surface to weaken the agglomeration effect of particles. Moreover, the steric repulsion force is generated due to the coating, making it very difficult to re-agglomerate the particles. Modifiers used for coating modification include surfactants, superdispersants, inorganic substances, etc.

Using tartaric acid as the surfactant, the influence on the flow properties of SiC slurry was studied. The results show that the amount of tartaric acid has a great difference in the effect of the surfactivity of silicon carbide powder. Generally speaking, when the amount of tartaric acid is used is 0.05%, it has the best effect on the surface modification of silicon carbide.

Surface modification strategies of inorganic powder: rheological performance, dispersion and functional improvement

The carbon black was modified with super dispersant. The results showed that the addition of super dispersant significantly improved the dispersing properties of the system. Under the optimal dispersant content, the system had high flow, low viscosity, and small thixotropy properties.

The inorganic silica layer coated on the surface of calcium carbonate can make it have the properties of silica to a certain extent, and the surface smoothness, whiteness, acid resistance, dispersion, specific surface area, etc. are greatly improved, which can greatly improve the application performance of calcium carbonate.

Modification effect of polyethyleneimine (PEI)

The surface modification of polyethyleneimine (PEI) can improve the flow performance of SiC powder. The modified particles are uniform in size and are mostly spherical in shape. Adjusting pH changes the binding method of polyethyleneimine and SiC particles. Polyethyleneimine adsorbs to the surface of SiC particles, increasing the electrostatic repulsion between the particles, which helps improve the dispersion and fluidity of the SiC particle surface.

Research on the modification of polyethylene glycol as a dispersant

The surface modification treatment of industrial SiC powder was performed using polyethylene glycol as a dispersant. The flow characteristics, adsorption, thermal gravity, and morphology of SiC powder before and after modification were studied through TG, IR, electron microscopy, and other testing techniques. The effects of polyethylene glycol addition and the liquid medium on various physical properties were analyzed.

The experimental results show that when the addition amount of polyethylene glycol is 5% (mass fraction) and the medium is ethanol, the modified SiC powder has good flow characteristics. After the modification, the particles are dispersed better, the size is uniform, and the shape is mostly block-like. Moreover, the sintering performance of silicon carbide ceramic products after the powder is modified has also been improved.