Manufacture and Properties of Salt Balls as Space Holder for Open-cell Metallic Foams

Abstract

Open-cell metallic foam is an attractive material to industries, owing to its outstanding properties, such as interconnected porosity, light weight, large surface area and high service temperature. One of popular methods to produce this foam is by using space holder to create porosity in foam structure, owing to its simplicity and low manufacturing cost. Among various space holder materials, NaCl is the most widely used one, due to low cost, high melting point, rapid dissolution by water and environmental friendly. In the present project, spherical NaCl balls of three different sizes have been manually manufactured by hand. The balls were sintered to increase their mechanical strength. Dissolution ability, macro- and microstructural examination as well as compressive mechanical testing were also performed. The smallest NaCl ball was then selected in production of Al foam. The result showed that the NaCl ball can be used to produce open-cell Al foam with interconnected spherical pores, replicating the morphology of NaCl ball. In addition, apart from spherical shape, various morphology of salt balls can be tailored to produce a metallic foam with specific porous structure, in order to obtain specific properties.