At present, there are many methods for surface modification, and the classification method varies depending on the angle of analysis of the problem. The powder surface modification methods are divided into six categories, namely: surface coating modification, surface chemical modification, mechanical force chemical modification, capsule modification, high energy modification, and precipitation reaction modification.

Let us introduce the principle and function of surface coating modification. The surface coating modification is that the surface modifier has no chemical reaction with the surface of the particles, and the coating and the particles are connected by physical methods or van der Waals forces, and the method is almost suitable for surface modification of various inorganic particles. This method mainly uses an inorganic compound or an organic compound to surface coat the particles, weakens the agglomeration of the particles, and generates a steric repulsion force due to the coating, so that re-agglomeration of the particles is very difficult. The modifier used for the coating modification is a surfactant, a hyperdispersant, an inorganic substance, or the like.
Zhao Haiyan and others used tartaric acid as a surfactant to study the effect on the flow properties of SiC slurry. The results show that the amount of tartaric acid has a great influence on the surface activity of silicon carbide powder. In general, tartaric acid has the best surface modification effect on silicon carbide at a dosage of 0.05%. Hu Shengfei et al. used a polyester hyperdispersant to modify nano-calcium carbonate and used the paste viscosity of the plasticizer to characterize the fluidity and dispersibility of the filler nano-calcium carbonate in the resin. The smaller the viscosity of the system, the better the modification effect. The paste viscosity of the modified nano calcium carbonate is greatly reduced. Chen Feiyue et al. modified the carbon black with a hyperdispersant. The results showed that the addition of the superdispersant significantly improved the dispersion performance of the system. Under the optimal dispersant content, the system has high fluidity, low viscosity and small thixotropic. Other nature. Yue Linhai and other coatings on the surface of calcium carbonate coated with inorganic silica can make silica properties to a certain extent. Surface smoothness, whiteness, acid resistance, dispersibility, specific surface area, etc. Improve, can greatly improve the application performance of calcium carbonate. Prabhakaran et al. studied the surface modification of aluminum hydroxide-coated SiC powder. When the coverage of aluminum is 0.1 mg / m 2 , the SiC powder exhibits a dispersion characteristic similar to that of alumina, and the zeta potential is remarkably improved; when the aluminum of the coating layer is increased to a certain value, the rheological property of the suspension is lowered. The surface modification of polyethyleneimine (PEI) can improve the flow properties of SiC powder. The modified particle size is uniform and the shape is mostly spherical. The pH is adjusted to change the combination of polyethyleneimine and SiC particles. The adsorption of polyethyleneimine onto the surface of SiC particles increases the electrostatic repulsion between the particles and helps to improve the dispersibility and fluidity of the SiC particles. The surface modification of industrial SiC powder was carried out by using polyethylene glycol as dispersant. The flow characteristics, adsorption, thermogravimetry and morphology of SiC powder before and after modification were studied by TG, IR and electron microscopy. The influence of the amount of polyethylene glycol added and the liquid medium on various physical properties was analyzed. The test results show that: the addition amount of polyethylene glycol is 5% (mass fraction). When the medium is ethanol, the flow characteristics of the modified SiC powder are better. After the modification, the particles are well dispersed, the size distribution is uniform, and the shape is mostly The block distribution and the sintering properties of the silicon carbide ceramics after the powder modification are also improved.

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