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Sintered metal porous material |
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 Overview
Porous materials, as the name suggests, are materials with many holes that form interconnecting or isolated networks of material and pores. If the pores are interconnecting, the material is called open-pored, whereas if the pores are completely separated, the material is called closed-pored. Some pores may be partially open or closed.
Porous materials are common in nature and have excellent mechanical properties that make them widely used. The most common examples are wood and honeycombs, which contain many small cavities. Basic porous materials like these have been used for construction, including in the ancient pyramids of Egypt and as stoppers for wine bottles in ancient Rome. Human bones can also be classified as porous materials with low density and high mechanical strength.
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In modern times, humans have begun manufacturing porous materials, the simplest of which are honeycomb structures made up of many similar diamond-shaped holes used for lightweight structures.
Porous materials are processed using powders, mesh, or fibers organized in a specific way. They contain many directional or random holes. These holes can be designed in various shapes such as foamy, lotus-shaped, honeycomb-shaped, etc.
Porous materials have characteristics such as low density, good rigidity, high strength-to-weight ratio, and good sound absorption and vibration damping properties. Continuous porous materials have additional characteristics such as good permeability and aeration. Porous materials have both structural and functional characteristics.
According to the different raw materials, such as powders, mesh, or fibers used in the production process, porous materials can be defined as different types of materials, such as sintered metal porous materials, ceramic porous materials, and non-metallic porous materials.
The main characteristics of metal porous materials are as follows:
 Permeability, permeation and adsorption
Porous materials have good permeability and selective permeation and adsorption. Pores can allow the passage of gas and liquid media. Porous materials with regular shapes and arrangements, and controllable pore size and direction, have been manufactured. Porous materials can be used for filtration and separation, and special reusable filtration and separation devices can be manufactured to filter or separate various media.
Mechanical properties
Due to the large number of pores in porous materials, their density is significantly reduced. For example, the density of porous steel can be reduced by 34.2% compared to dense materials. The density of porous aluminum or magnesium alloys can be less than 1 g/cm3. Porous materials rolled into sheets can be used to make the skins of cars and machines, replacing the currently used sheet materials. They also have a large advantage in aerospace and aviation. If some dense materials in airplanes are replaced with porous materials, their weight can be significantly reduced while maintaining the same performance.
Energy absorption characteristics
Porous materials have many functions that dense materials are difficult to achieve, such as energy absorption and buffering. The propagation of mechanical waves and mechanical vibrations in porous materials with pores will change. When the wave propagates to the interface between the dense part and the pore, reflection and refraction occur. Porous materials can play a blocking role due to the existence of pores, which increases the opportunities for reflection, refraction, and diffraction. Porous materials can be used to make sound insulation materials, vibration reduction materials, and anti-explosion and impact materials. By using the energy absorption characteristics of metal porous materials, energy absorbers, shock absorbers, etc., can be manufactured and applied in mechanical engineering and vehicle engineering to avoid or reduce malignant accidents when they receive sudden impact.
Optoelectronic properties
Powder metallurgy porous materials have unique optical and electrical properties. For example, porous silicon with micro-pores can emit visible light under laser irradiation and is expected to become an ideal material for manufacturing new optoelectronic components. By using the unique optoelectronic properties of porous materials, porous electrodes for fuel cells can be made, which are considered as a promising next-generation automotive energy device.
Chemical properties
Due to the large number of pores in powder metallurgy porous materials, their activity generally increases. Porous materials with molecular recognition functions can produce artificial enzymes, which can greatly increase the speed of catalytic reactions. Due to the existence of pores, the mechanical properties of sintered porous materials may not be as good as those of dense metals, but their specific surface area is larger, and some properties are much better than those of dense metals, such as heat exchange capacity, electrochemical activity, and catalytic performance. Porous materials also have advantages such as high heat transfer efficiency, electrochemical activity, sound resistance, and resistance to media corrosion.
Vibration damping properties
The large amount of gas inside the powder metallurgy porous material makes it possible to dissipate a lot of energy generated when the material receives energy from the vibration source inside the material. Powder metallurgy porous materials also have good sound absorption capacity, so they are widely used as noise isolation materials, such as aluminum alloy porous materials and magnesium alloy porous materials, which can be used in the inner partition walls of submarines to prevent sonar tracking. The ceiling used in crowded places can greatly reduce noise. In the future, this material can also be used in vehicles such as cars to reduce engine noise.
Other properties
Powder metallurgy porous materials also have properties such as controllable pore size and porosity, thermal conductivity, electrical conductivity, weldability and processability, electromagnetic wave absorption characteristics, and sensitivity to gases. Therefore, powder metallurgy porous materials have broad prospects for application in fields such as communication engineering and environmental engineering. Porous artificial bone made by developing powder metallurgy porous materials using simulation technology has biomaterial characteristics, so it can be used as an ideal bone material for the human body.
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Classifications
Sintered porous stainless steel Sintered porous titanium Sintered porous nickel and nickelalloy
Porous intermetallic compounds Sintered porous wire mesh |
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