Research On Porous Composite Of NiAl Inter-Metallics By The Combustion Synthesis

Combustion synthesis technology is one of the most new attractive technologies toprepare the materials. This dissertation discussed the application of CS technology in the fieldof porous intermetallics/ceramic composites. In this dissertation, high-porosity NiAlintermetallics with Ni and Al powders by means of CS. On the basis of the fundamentalresearch, NiAl/TiB₂-Al₂O₃ composites were prepared by adding different ratio Al, TiO₂ andB₂O₃. In the composite, NiAl intermetallics were matrix and TiB₂-Al₂O₃ ceramics werereinforcer in order to improve the high-temperature strength. Moreover, porosity, pore size andpore shape were improved by addition of different pore-creating materials in order to satisfythe different requires of tail gas purifier carrier in different conditions. And found the optimalsynthetic method. By analyzing the result of X-ray diffraction, we could find the reactants withNi-Al intermetallics had mainly NiAl, Ni₃Al and Ni phases; After adding the ceramic system,the reactants have mainly NiAl, Ni, TiB₂ and Al₂O₃. The results indicated that the reaction ofceramic system is complete.Ni-Al and NiAl/TiB₂-Al₂O₃ composite were analyzed by EDS and SEM. It could befound as follows: Ni₃Al distributed in NiAl matrix with a phase of strip among Ni-Al reactionproducts. After added 15wt% ceramic system, Al₂O₃ appeared no regular shapes and TiB₂appeared in irregular dendritic structure, distributing in reticulation on NiAl matrix. Afteradded 33wt% ceramic system, TiB₂ appeared in regular shapes, such as regular cube,hexagonal prism and rod. Its average grain sizes were about 2～10μm. Most of the pores in theNi-Al reaction products were pylome, which had intercommunicating pores and zigzag porepassages. Pore sizes of Ni-Al reaction products were about 10～100μm, and after added 15wt%ceramic system pore sizes became 20～200μm. Pore size enlarged apparently by adding pore-creating agent. The minimal pore size was 50μm and maximal pore size was 430μm. Averagepore sizes had great discrepancy. The microhardness of Ni-Al reaction products was about300～650HV and it could be improved to above 1000HV after adding ceramic system. Thesebasic researches were of guidance for optimizing synthetic techniques, by which porouscomposite with perfect properties might be obtained.