Metal Foam - metal that breathes
Due to its special structure, it possesses special properties in many aspects. As a structural material, it is characterized by light weight and high specific strength; as a functional material, it has a variety of physical properties such as porous, vibration damping, damping, sound-absorbing, sound insulation, heat dissipation, impact energy absorption, electromagnetic shielding and so on.
Foam metal is prepared by powder metallurgy method and electroplating method, the former by adding foaming agent to the molten metal to produce foam metal; the latter by electrodeposition process on the polyurethane foam skeleton replicated into foam metal.
Powder metallurgy method to make foam metal, is added to the powder blowing agent (such as NH4Cl), sintering the blowing agent volatilization, leaving pores. Foam metals with regular shaped pores and porosity as high as 95% can be made by electrochemical deposition, including foam materials with metals and alloys such as Cu, Ni, NiCrFe, ZnCu, NiCu, NiCrW, NiFe, and other metals and alloys as the skeleton. The metal electrochemically deposited on the porous body is sintered so that the deposited components are connected as a whole, and the strength is up to the required highly porous foam metal with high porosity, which can be filled with more substances such as catalysts and electrolytes in use.
Aluminum, nickel and their alloys have been practical foam metal, in addition, the foam copper also has a certain space for development.
Foam aluminum and its alloys are lightweight, with sound absorption, heat insulation, vibration damping, absorption of impact energy and electromagnetic waves and other characteristics, suitable for missiles, aircraft and its recovery parts of the impact of the protective layer, automotive buffers, electronic machinery vibration damping devices, pulse power electromagnetic wave shielding cover.
Nickel foam has high gas permeability, high specific surface area and capillary force due to its connected pore structure and high porosity, and is mostly used as a functional material for making fluid filters, atomizers, catalytic converters, battery electrode plates and heat exchangers.
Copper foam conductivity and ductility is good, and the preparation cost is lower than nickel foam, better conductivity, can be used for the preparation of battery negative electrode (carrier) materials, catalyst carriers and electromagnetic shielding materials. In particular, copper foam for batteries as electrode substrate materials, has some obvious advantages, but due to the corrosion resistance of copper is not as good as nickel, thus also limiting some of its applications.
This material has long been used as a core material for aircraft clamping components. In the aerospace and missile industry, can be made into a sandwich bearing components, such as for the wing metal shell of the support body, missile nose cone of the shell of the high-temperature collapse of the support body (because of its good thermal conductivity) and the landing gear of the spacecraft. In construction, foam metal is needed to make light, hard, fire-resistant elements, railings or support bodies for these things. The high-frequency, high-speed acceleration and deceleration of modern elevators also requires lightweight structures with both energy-absorbing and load-carrying properties to reduce energy consumption. Cushioning is also one of the main uses of foam metal, which must have the ability to absorb energy while keeping the maximum force acting on the protected object below the limit of causing damage.