metal, porous

Lightweight metal made by melting metals such as copper, or iron alloys, in a sealed furnace filled with hydrogen, or other gas, under pressure. The formation of pores can be controlled by varying pressures and cooling times. They vary in density from 5% to 75% of the metal and in diameter from 5 micrometres (millionths of a metre) to 10 mm/0.39 in. The direction and positioning of the pores can also be controlled.

Porous metals were developed in the Ukraine in the 1960s and used in space rockets. Kerosene was forced through the pores to form a fine mist for optimum combustion.