Preliminary Studies and Researches on the Elaboration of Gradual Porous Sintered Structures by Powder Sedimentation

Spherical bronze powders were used for studies the obtaining of gradual porous structures by sedimentation and sintering methods. The powder size classes above 100 mu m were used for the manufacturing of the macroporous support by spreading the powder into the sintering die. Sintering was conducted in vacuum (10(-4) Torr) at a temperature of 750 degrees C for 40 minutes. On the macroporous support a layer of fine powder fraction was deposited by gravitational sedimentation. The deposited layers were consolidated by sintering at 750 degrees C for 30 minutes. The analysis of the gradual porous layers was done using scanning electron microscopy and mercury porosimetry. The fluids viscosity influences the sedimentation velocity of particles. The height of the column directly affects the quality of porous structure. If the sedimentary column is short, the turbulences created by adding the suspension of the dispersed powder in the sedimentary tube are more harmful.