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Chemical Syntheses of Nanocrystalline Nickel Aluminides
journal contribution
posted on 2000-03-30, 00:00 authored by Joel A. Haber, Nilesh V. Gunda, John J. Balbach, Mark S. Conradi, William E. BuhroNanocrystalline nickel aluminides (nano-NiAl and nano-Ni3Al) are synthesized by reactions
of NiCl2 and LiAlH4 in Et2O or 1,3,5-trimethylbenzene, followed by annealing of the reaction
products at 550−750 °C. The reaction pathways followed in the two solvents differ, leading
to nanocrystalline materials of different composition and microstructure. The nanocrystalline
nickel aluminide powders are highly susceptible to adventitious oxidation, which produces
Al2O3. Consolidates obtained by hot pressing the powders at 700−1200 °C and 350−650
MPa in an Ar atmosphere contain 8−23 wt % Al2O3. They possess densities of 80−98% of
theory, and Vickers microhardnesses of 4.0−6.3 ± 0.3 GPa. Hot-pressing temperatures of ≥
1200 °C are required to produce consolidates having good environmental stability. Consolidates are also produced by hot pressing admixtures of nano-Ni and nano-Al, with and without
added nano-AlN as a second, reinforcement phase. The resulting nanocrystalline and
nanocomposite nickel aluminides exhibit the highest purities, densities, and hardnesses (up
to 7.4 ± 0.9 GPa) among the samples studied.
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chemical SynthesesdensityNiCl 2GPareinforcement phaseAl 2 O 3Et 2 Oreaction pathwaysLiAlH 4Nanocrystalline Nickel Aluminides Nanocrystalline nickel aluminidesnanocrystalline materialsConsolidatenanocrystalline nickel aluminide powdersVickers microhardnessesnanocomposite nickel aluminides exhibitreaction productsAr atmosphere
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