Production of Porous Aluminium Using Sodium Chloride

Abstract

Our workplace, Technical University of Liberec, is currently engaged in research and production of cellular metal systems. Basically, cellular metal systems are materials with lower density. It is a research in the field of mechanical engineering that is focused on the development of new materials. In general, many methods have been developed for the production of cellular metal systems, e.g. by BANHART [2] or ASHBY [4]. At their production, the direct gassing of molten metals (mostly aluminium ones) or gassing by the powder agents (e.g. specially formulated aluminium powders) are mostly used. Depending on the manufacturing method, a cellular system with open or closed cells can be obtained. The most commonly used metal is aluminium and its alloys. We are currently focusing on the production of porous aluminium by using sodium chloride. Sodium chloride occupies regular sites in the aluminium material and thus contributes to the aluminium porosity. After solidification of the aluminium, sodium chloride is dissolved in water. Sodium chloride is relatively inert to the aluminium and together with it, has a favourable density (2160 kgm-3) compared to the aluminium density (2700 kgm-3). The values of these physical quantities were observed on the produced aluminium test specimens having  60 x 10 mm: relative density of porous system REL; porosity of metal system P; amount of solid phase system volume fraction VPM; density of porous metal system PM and porous material Young's modulus of elasticity EPM.

Characteristics of Porous Aluminium Materials Produced by Pressing Sodium Chloride into Their Melts

“…The first experiments provided preliminary information demonstrating possibilities in the production of aluminum porous materials. These results of the first findings were already published in [27].…”

“…The researchers of [26] studied the mechanical properties of aluminium foams. In [27], the production of porous aluminium materials by means of pressing an aluminium alloy melt among the grains of sodium chloride was investigated. In this way, it was possible to produce circular samples with quite small height (60 mm × 10 mm).…”

Monitoring the influence of sodium chloride particle size on the physical, me-chanical properties and structure of samples of porous aluminium materials

“…Another research work [23] focussed on corrosion effects for aluminium alloys, which are the basis of the production of porous materials. Our published work [24] deals with the monitoring of other possibilities for porous aluminium material production and the evaluation of their physical properties of such producced materials. The evaluation of the properties of porous materials was also dealt with by LUNA [6] and the most common physical quantities were found to be: the actual density, which is the density of the material without pores or cavities; bulk density is the density of the material, including open pores and cavities; pore volume is the addition of individual pore volumes; pore size is the distance between the walls of the pores, their width or diameter; porosity is the relationship between the total pore volume to the apparent volume of a sample or particle and the final surface area, which is the surface area of the non-porous material.…”

“…This method was used e.g. in publication [24] in which the production of porous aluminium material by pressing the melt between sodium chloride particles and evaluating the properties of the material produced was introduced. This publication presents the results of the production of an aluminium porous material by pressing sodium chloride particles into this melt.…”

“…To evaluate the properties of the produced porous aluminium materials, we developed a methodology which was published [24]. This methodology is primary used for determining of the relevant physical and material characteristics, respectively relevant quantities.…”