Research On The Preparation And Properties Of Porous Nial Material

In this paper, porous NiAl intermetallics were prepared by Combustion synthesis from Ni and Al powders. The pore wall is rough. The pores are well distributed and connect in three dimensions, showed equiaxial or approximate equiaxial appearance. Macro-pore NiAl materials with three-dimensional connectivity structure were prepared by compact pressing and insitu reaction technology with pore forming agent. The shape of synthesized samples is similar to the original samples in cylinder.NiAl intermetallics with high porosity were prepared by adding TiH2 as pore foaming agent. The porosity of the products is more than 50%. The pore size is uneven. Macro pores appeared. The pore structure is even more complex with better connectivity. The porosity of the products rises consistently with the content of TiH2 pore forming agent rising, and compression strength increases too.Porous NiAl materials with three-dimensional connectivity structures were prepared by adding different size of urea as pore forming agent. The pores and the forming process were studied. The macro-pore NiAl materials formed by compact pressing technology with urea were observed under Scanning Electron Microscope (SEM). The results show that the macro pores are similar to the morphology of urea. The average pore size is in the range of 0.15-2mm. There are large quantities micro pores distributed well in the wall of macro pores, which synthesized in the reaction process. So the connectivity of porous materials improves. The porosity of different four experiment products were measured. The relation between real porosity and the theoretic porosity were studied. The results show that the real porosity is lower than the designed porosity.Porous NiAl materials were prepared by combustion synthesis with different size of Al powder. The products are in the form of particles accumulation, and the particle size is unevenness. Different lengths and criss-cross shaped fibers were detected in some pore wall of Porous NiAl materials. The larger the size of the pore is, the longer and more the fiber is. With the size of Al particles increasing, the level of the accumulation will be bigger, and the volume of the porous particle-accumulation NiAl materials decreases. The pore structure becomes more complex, and the pore size becomes tiny. To some extent, the specific surface area enhances greatly. The whiskers, criss-cross in different length growing in the pore walls, were detected. The content of whisker increases with Al grain size increasing, and the whisker grows even longer.