Yuan Lei tells you | one article to understand the surface modification technology of ultrafine powder!

Release time:

2024-01-29 09:35


Yuan Lei tells you | one article to understand the surface modification technology of ultrafine powder!


Ultrafine powders usually include micron (1 ~ 30μm), sub-micron (0.1 ~ 1μm) and nano-scale (1 ~ 100nm) particles. Because of the surface effect and volume effect different from the original solid material, it shows unique optical, electrical, magnetic, thermal, catalytic and mechanical properties, etc, moreover, it shows broad application prospects for the composite and development of new functional materials, and has a wide range of applications in various fields of the national economy.


Why do ultrafine powders need surface modification?


Due to the small particle size and high surface energy of ultrafine powder, it is easy to agglomerate and form secondary particles, which can not show the surface area effect, volume effect and so on. Powder agglomeration makes it often lose many advantages of ultrafine powder in the process of use, so that its effectiveness can not be fully exerted.


In order to solve the problem of agglomeration of ultrafine powder and improve its dispersion and rheological properties, the most effective method is to modify the surface of the powder.The surface modification of the powder can increase the repulsion between the powder particles, reduce the attraction between the powder particles, make it easy to disperse, and improve the application performance of the powder.


The purposes of surface modification include:

  • Improve or change the dispersion of powder particles;

  • Improve durability, such as resistance, light resistance, heat resistance, weather resistance, etc;

  • improve particle surface activity;

  • The particle surface produces new physical, chemical and mechanical properties and new functions, thereby increasing the added value of the powder.


2. Surface modification method of ultrafine powder


There are many methods of surface modification, which can be generally divided into: surface coating modification, surface chemical modification, mechanical force chemical modification, capsule modification, high energy modification, precipitation reaction modification.


(1) Surface coating modification


Surface coating modification is that there is no chemical reaction between the surface modifier and the particle surface, and the coating and the particle are connected by physical method or van der Waals force, which is almost applicable to the surface modification of all kinds of inorganic particles. This method mainly uses inorganic compounds or organic compounds to coat the surface of the particles, which weakens the agglomeration effect of the particles, and the steric repulsion force is produced due to the coating, which makes it very difficult for the particles to reunite. Modifiers for coating modification include surfactants, hyperdispersants, inorganic substances, etc.


(2) surface chemical modification


Surface chemical modification is to modify the surface of particles by adsorption or chemical reaction of functional groups in organic molecules on the surface of inorganic powder. In addition to the use of surface functional group modification, the method also includes the use of free radical reaction, chelating reaction, sol adsorption and other surface modification.


(3) mechanical force chemical modification


Mechanical force chemical modification refers to through crushing, grinding, friction and other mechanical methods, so that the mineral lattice structure, crystal type and other changes, the system can increase, the temperature rises, promote the dissolution of particles, thermal decomposition, produce free radicals or ions, enhance the surface activity of minerals, promote minerals and other substances to react or adhere to each other, to achieve the purpose of surface modification.


(4) capsule type modification


Capsule modification is a surface modification method that covers the surface of powder particles with homogeneous and certain thickness film.


(5) high energy modification method


The high-energy modification method is a method of effecting modification by initiating a polymerization reaction by plasma or radiation treatment.


(6) Precipitation reaction modification


The precipitation reaction method is to add a precipitant to a solution containing powder particles, or add a substance that can initiate the generation of the precipitant in the reaction system, so that the modified ions are precipitated on the surface of the particles, thereby coating the particles. The precipitation method can be divided into direct precipitation method, uniform precipitation method, non-uniform nucleation method, co-precipitation method, hydrolysis method and so on.


3. Factors affecting the effect of surface modification


The main factors affecting the effect of powder surface modification are the nature of powder raw materials, surface modifier formulation, surface modification process, surface modification equipment, etc.


(1) Properties of raw materials


The specific surface area, particle size and particle size distribution, specific surface energy, surface physical and chemical properties, and agglomeration of powder raw materials all have an impact on the surface modification effect, and are one of the important factors for the selection of surface modifier formulations, process methods and equipment.


(2) Surface modifier formulation


The surface modification of powder is realized to a large extent by the effect of surface modifier on the surface of powder, therefore, the formulation of surface modifier (variety, dosage and usage) has an important influence on the modification effect of the powder surface and the application performance of the modified product. The formulation of the surface modifier includes the selection of varieties, the determination of dosage and usage..


(3) Surface modification process


After the surface modifier formulation is determined, the surface modification process is one of the most important factors that determine the effect of surface modification. The surface modification process should meet the application requirements or application conditions of the surface modifier, the dispersion of the surface modifier is good, and the surface modifier can be uniformly and firmly coated on the surface of the powder; at the same time, the process is simple, the parameters are controllable, the product quality is stable, and the energy consumption is low, the pollution is small.


(4) Surface modification equipment


When the surface modifier formulation and modification process are determined, the surface modification equipment becomes the key factor affecting the surface modification or surface treatment effect of the powder. The high-performance surface modification machine should be able to make the dispersion of powder and surface modification agent good, powder and surface modification agent contact or equal opportunity; at the same time, can easily adjust the modification temperature and reaction time, unit product energy consumption and low wear, no dust pollution, simple operation of the equipment, smooth operation.

Modification, surface, modifier, method, particle, granule, reaction, formula, ultrafine powder

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