Hole classification in pore size distribution - Database & Sql Blog Articles

Classification of holes: 1. According to whether it is connected with the outside, the holes can be divided into open holes and closed holes. The cavity and the hole that communicate with the outside are called open holes, and the one that does not communicate with the outside is called closed hole. The creation and morphology of open and closed cells can be controlled as needed during process preparation or processing. 2. According to the size of the pore diameter: large pores, medium pores (mesopores), micropores. This is based on the size of the pore diameter according to the International Union of Pure and Applied Chemistry (IUPAC). Large pores (φ ≥ 50 nm or 500 Å); medium pores (2 nm or 20 ≤ φ ≤ 50 nm or 500). The middle hole is also called the transition hole, and there is no division of the middle hole or the small hole, collectively referred to as the middle hole or mesoporous; micro hole (φ≤2nm or 20?); 3. According to the geometry of the hole: ink bottle hole, wedge hole, Columnar holes, etc. Q: What is a hole? Classification of holes? Why is the more complex the pore morphology of the material and the more developed the pores, the stronger its adsorption of gas? A: To answer this question, we must first define and classify the holes. What is a hole? In our production, life and scientific research, we can access various materials. In addition to a small number of dense materials such as steel and glass, most of the materials have some internal channels. These holes have different names in different disciplines. The meaning is different. In the study of porous materials, pores refer to open and closed pores in the material. Among them, the cavity and the hole communicating with the outside are called the opening, and the one not communicating with the outside is called the closed hole. The concepts associated with it, such as pore size, pore volume, pore distribution, pore volume, etc., may occupy larger volumes than the material composition of the material itself, in various shapes, and in different diameters. The size and distribution of the throats of these holes and the various geometric shapes make the physical properties of the materials different, which has different uses. It is very important for the research of its preparation and processing. It is now popular. research content. The more developed the pores and the more complex the pore morphology, the larger the specific surface area inside the material. Taking activated carbon as an example, bamboo activated carbon prepared by KOH activation can have a specific surface area of ​​up to 2752 m 2 /g ("KOH activated high surface area bamboo activated carbon research" 1 gram of activated carbon contains a specific surface area, which can almost reach a standard football field. Due to the existence of intermolecular attraction (mainly van der Waals force), the gas molecules passing through the pores in the material are attracted by the molecules on the surface of the pores inside the material, that is, adsorption occurs. When the specific surface area of ​​the material is larger, the pores passing through the pores The larger the contact area between the gas and the material, the more gas molecules can be accommodated, and when the pore morphology is more complicated, especially when the gas molecule diameter is slightly smaller than the pore diameter of the material, the gas molecules encounter the pore surface. After the material molecules are very difficult to run out, that is, they are not easily detached. In this case, the more developed the pore structure, the more complicated the pore morphology, especially when the proportion of micropores is large, the specific surface area of ​​the material is larger, so the unit mass is The greater the amount of gas adsorbed by the material, the stronger the adsorption of the material to the gas.