Porous aluminum has a unique combination of properties.

Because of this he is a promising material for various applications. In many cases, a porous aluminum are superior to other porous materials – sintered bronze, sintered steel, porous ceramics.

Features a porous structure

Porous aluminum is manufactured through casting. The porous structure is formed after the extraction of the filler (salt) from the aluminum matrix. In the first step of salt particles fill the form for casting. Then, molten aluminum penetrates into the voids between the particles, and metal solidifies there. Liquid aluminum does not penetrate into the contact area between the salt particles. Therefore, each pore connected with all adjacent pores after salt dissolution. The filtered medium (gas or liquid) passes in any direction through these pores.

Model and photo of porous aluminum structure

structure-of-porous-aluminum

D max is the diameters of the salt particles. By setting different D max, we can obtain a porous aluminum with different properties. Typical values of D max is 0.14-0.35 mm, 0.35-0.63 mm, 0.35-1.00 mm, 0.63-1.6 mm, 0.63-3.00 mm

The porosity and density of porous aluminum

The value of a typical porosity is approx. 50%. This means that the proportion of air pores of 50% by volume of the material. This porosity is achieved for any typical D max values. The density of porous aluminum in this case is 1.35 g/cm3 (84 lb/ft3).

If we use a combination of two standard D max values, it is possible to achieve up to approx. 65% porosity. The density of porous aluminum in this case is 0.95 g/cm3 (59 lb/ft3).

Filter grade

D max, mm              0.14-0.35     0.35-0.63     0.35-1.00     0.63-1.60     0.63-3.00


Filter grade, µm         5-10             40-60           80-110        120-150        200-250

Strength of porous aluminum

Compressive strength

D max, mm                                     0.14-0.35     0.35-0.63     0.35-1.00     0.63-1.60     0.63-3.00


Compressive strength, N/mm2        36-42            26-30           22-26           19-23           18-22

Tensile strength

D max, mm                                     0.14-0.35     0.35-0.63     0.35-1.00     0.63-1.60     0.63-3.00


Tensile strength, N/mm2                  25-27           15-17           14-16           10-12            7-9

 

Permeability of porous aluminum

D max, mm                                     0.14-0.35     0.35-0.63     0.35-1.00     0.63-1.60     0.63-3.00


Permeability coefficient K, m2          ≥7×10-12      ≥3×10-11      ≥8×10-11      ≥1.5×10-10   ≥2.5×10-10

According to Darcy’s law:

Q = K*∆P*S/µ/h,

where Q – flow, m3/sec, K – permeability coefficient, m2, ∆P – pressure drop, Pa, S – filtration surface area, m2, µ – dynamic viscosity, Pa*sec, h – filter thickness, m