Introduction of porous materials

Solids containing a certain number of holes are called porous materials, which are materials with network structure composed of interconnected or closed holes, and the boundaries or surfaces of the holes are composed of columns or plates. One of the typical hole structures is that a large number of polygonal holes are gathered on one plane.

The two-dimensional structure formed by aggregation is called "honeycomb" material because its shape is similar to the hexagonal structure of honeycomb. More popularly, it is called "foam" material, because there are a lot of polyhedral holes in the space. Some documents claim that the porosity is sufficient as a porous material, and the porosity is greater than that as a foam material. However, from a large number of domestic and foreign documents, the porosity of this foam material is not greater than that of the well-known aluminum foam, and its porosity is often lower. Some documents say that the porosity is from one to the same, while others think that the material was originally prepared by foaming method, so it was once called foam material, and later it was developed by infiltration and other preparation methods, which was called breathable material. A more appropriate name should be porous foam material, or simply foam material. In short, there is no uniform, strict and accepted definition. Most scholars regard porous materials and foam materials as equivalent concepts. Porous materials are ubiquitous in nature, such as wood, cork, sponge and coral (the word cellulose comes from the Latin word "cell", which means "full of pores").

These natural porous materials have been widely used for thousands of years. Many years ago, the pyramids in ancient Egypt used wooden building materials, and cork was used as cork in Roman times. In modern times, people began to make their own porous materials, the simplest of which is a honeycomb material composed of a large number of similar prismatic holes, which can be used as light components. More common is polymer foam, which has a wide range of uses, from coffee cups that can be seen everywhere to shock absorbers in aircraft cabins. With the development of modern science and technology, metals, ceramics, glass and other materials can also foam like polymers. These new foam materials are gradually used as materials for heat insulation, buffering and absorbing impact energy, thus exerting their unique comprehensive properties determined by porous structure.