The porous material refers to a material constituting a network structure by pores penetrating or closing each other.

A solid with a certain number of pores is called a porous material, and the boundary or surface of the pores is composed of columns or plates. The general pore structure has a large number of polygonal pores gathered on the plane to form a two-dimensional structure, the shape of which is similar to the hexagonal structure of the honeycomb, so it is called "honeycomb" material.

More commonly, many polyhedrally shaped pores gather in space to form a three-dimensional structure, often referred to as a "foam" material. Some literature refers to things that are sufficiently porous as porous materials, and things that are more porous than porous materials are called foams. From many domestic and foreign literature, the porosity of the so-called foam material is not larger than the porosity of the porous material. For example, it is well known that the porosity of aluminum foam is often lower than that of porous materials. Some literature considers that low porosity is a 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, including wood, cork, sponge, coral, etc.

For thousands of years, these natural porous materials have been widely used by people. A few years ago, ancient Egyptian pyramids already used wooden building materials, and cork from Roman times was used as a cork for wine bottles. Modern people are beginning to make their own porous materials, the simple of which can be used as lightweight parts of honeycomb materials composed of similar prism holes. More common is the polymer foam material, its wide range of uses, can be used everywhere in the coffee cup, aircraft cabin and other large shock pads.

The development of modern technology enables metals, ceramics, glass and other materials to fire like polymers. These new foam materials are gradually used as materials to absorb insulation, cushioning and impact energy, and play a unique comprehensive performance determined by the porous structure.

The powder raw material for making porous materials can choose spherical and irregular powder or metal fiber according to the application and performance requirements. The use of spherical powder can easily obtain porous materials for filtration and flow control with low fluid resistance, uniform structure, and good regeneration, but the mechanical properties of this powder product are not as good as those of irregular powder products. Irregularly shaped powders or fibers are used to make highly porous materials. In order to obtain the porous structure caused by the overlapping of powder particles, the molding pressure and sintering temperature for manufacturing porous materials are usually lower than those for manufacturing sintered dense materials.

The pore size, strength, and other properties of the porous material depend on the average particle size, particle size distribution, particle shape, and the like of the selected powder. In order to manufacture materials with predetermined properties, it is usually necessary to process the powder in advance, including annealing, particle size grade, selection of spheres and balls, and addition of various additives (manufacturing agents, lubricants, plasticizers). In addition to the general cold pressing-sintering process, the molding process can also select invoice sintering (simple release agent), powder rolling (thickness 0.1~3mm plate, belt, pipe), extrusion (special-shaped charging products), isostatic pressing preparation (special-shaped large products) according to the shape and size of the product.