Specific surface is the ratio of the surface of a substance to the surface area inside a substance per unit mass or unit volume. It is an important physical property and has a wide range of applications in chemistry, materials, environment, and other fields. This article will introduce in detail the definition and concept of specific surface, calculation methods, measurement techniques, application fields, influencing factors, calculation formulas, and properties of matter.
1.Definitions and concepts.
Specific surface refers to the surface area corresponding to the inside of a substance per unit mass or unit volume, also known as surface area ratio or specific surface area. It reflects the porosity and surface properties inside the substance, and is of great significance for understanding the physical, chemical and adsorption properties of the material.
2.Calculation method:
There are several main methods for calculating the specific surface:
Planar method: Applies to substances with a flat or layered structure, and the specific surface is obtained by calculating the mass or volume per unit area.
Spherical method: Applies to substances with spherical particles, and the specific surface is obtained by calculating the number of particles per unit mass.
Irregular surface method: Applicable to substances with irregular surfaces, the specific surface is calculated by measuring the outer surface area and internal volume of the substance.
3.Measurement technology.
There are several main techniques for measuring specific surfaces:
Light Capture Method: Measuring the surface area of a substance by capturing the reflected and scattered light from the surface of the substance.
Image processing: The surface area is measured by taking a picture of the surface of the substance and using image processing software.
Volumetric method: The specific surface is calculated by measuring the internal volume of a substance and the volume of a solid.
4.Fields of application.
Specific surfaces have a wide range of applications in the following areas:
Chemistry: It is used to study the adsorption and catalytic properties of the surface of substances.
Materials: Used to study the relationship between the preparation, structure and properties of materials.
Environment: It is used to study the adsorption and catalytic processes of air purification, water treatment and other environmental treatment.
5.Influencing factors.
The main factors that affect the specific surface are as follows:
Solid shape: Different shapes of solid matter have different specific surfaces.
Thickness: The greater the thickness of a solid substance, the smaller the specific surface.
Material properties: Substances of different materials have different specific surfaces, such as metals, non-metals, and alloys.
6.Calculation formula.
The main formulas for calculating the specific surface are as follows:
Dubinin formula: suitable for porous substances, the specific surface is calculated according to the relationship between the pressure of the adsorbed gas and the amount of saturated adsorption.
Bet formula: The specific surface is calculated by measuring the amount of liquid nitrogen adsorbed, which is suitable for substances with a porous structure.
Principle of heterogeneity: Calculates the specific surface according to the mass and volume of different parts of the substance, and is suitable for substances with a multiphase structure.
7.Material properties.
The specific surface has the following effects on the properties of the substance:
Physical properties: Substances larger than the surface generally have high adsorption and diffusion properties, which affect the physical properties of the substance.
Chemical properties: Substances larger than the surface have higher chemical reactivity and are therefore able to participate in more chemical reactions.
Structural properties: The specific surface is closely related to the structure of the substance, such as porosity, particle size, etc., which affects the stability, mechanics and thermal properties of the substance.
In conclusion, as an important physical property, the specific surface is of great significance for understanding the nature and properties of matter, as well as for the development of new materials and the application of new technologies. Hopefully, the introduction of this article will help you better understand the knowledge and concepts that are more than superficial.