As an important physical property of powders, specific surface area refers to the total surface area per unit mass of oxide powder. And its size is influenced by various factors.
Firstly, particle size is an important factor affecting the specific surface area of powders. The smaller the particles, the larger the specific surface area. This is because the smaller the particle size, the larger the surface area of each individual particle, thereby increasing the total surface area per unit mass of powder.
Secondly, the shape of the powder also affects the surface area. The more complex the shape of the powder, the larger its specific surface area. For example, the specific surface area of porous oxides is often higher than that of non porous oxides of the same mass.
In addition, porosity is also one of the important factors affecting the specific surface area of powders. The higher the porosity, the larger the specific surface area. This is because the higher the porosity, the larger the surface area of individual particles, and the presence of pores can also increase the surface area of the powder.
There are many factors that affect the specific surface area of oxide powders, and these factors play important roles in the preparation and application processes.
1. Particle size
The particle size is the most direct factor affecting the specific surface area of oxide powder. At the same mass, the smaller the particles, the larger their specific surface area. This is because small particles have more surface atoms or molecules, thereby increasing the surface area of the entire powder. Therefore, by controlling the preparation process of particles, such as adjusting reaction conditions, selecting appropriate raw materials and additives, the particle size of oxide powders can be effectively adjusted, thereby affecting their specific surface area.
Particle refinement: Certain steps in the processing technology, such as mechanical grinding, ultrasonic dispersion, etc., can effectively reduce particle size, thereby increasing the specific surface area of the powder. This is because the specific surface area is inversely proportional to the particle size, and the smaller the particle, the larger its specific surface area.
Agglomeration control: During the preparation and processing, particles are prone to agglomeration, forming larger particle clusters, thereby reducing the specific surface area of the powder. Therefore, by optimizing the processing technology, such as adjusting the type and dosage of dispersants, controlling the pH value of the reaction system, and adopting appropriate drying and heat treatment methods, the agglomeration phenomenon of particles can be effectively controlled, and the specific surface area of the powder can be maintained or increased.
2. Particle shape
The particle shape also has a significant impact on the specific surface area of oxide powders. Among all geometric shapes, spheres have the smallest area to volume ratio, while particles with complex shapes such as flakes, needles, etc. have a larger specific surface area. This is because particles with complex shapes can expose more surface area at the same volume. Therefore, in the preparation process, by controlling the reaction conditions and the types and amounts of additives, the shape of the particles can be regulated, thereby changing the specific surface area of the powder.
3. Porosity rate
Porosity is the ratio of pore volume to total volume in oxide powder. The higher the porosity, the more pores there are in the powder, and the presence of these pores increases the surface area of the powder. Therefore, oxide powders with high porosity typically have a larger specific surface area. The regulation of porosity can be achieved by changing certain parameters in the preparation process, such as adjusting reaction temperature, time, pressure, etc.
4. Preparation method
The preparation method is one of the key factors affecting the specific surface area of oxide powders. Different preparation methods can lead to differences in the size, shape, and porosity of powder particles, thereby affecting their specific surface area. For example, the sol gel method can prepare oxide powders with high specific surface area, uniform particle size and fine size; The co precipitation method can optimize the specific surface area of the powder by controlling the precipitation conditions. Therefore, when selecting the preparation method, it is necessary to choose the appropriate process according to the specific application requirements.
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