Structure and phase-composition of Ti-doped gas atomized Raney-type Ni catalyst precursor alloys

Abstract

Raney-type Ni precursor alloys containing 75 at.% Al and doped with 0, 0.75, 1.5 and 3.0 at.% Ti have been produced by a gas atomization process. The resulting powders have been classified by size fraction with subsequent investigation by powder XRD, SEM and EDX analysis. The undoped powders contain, as expected, the phases Ni 2 Al 3 , NiAl 3 and an Al-eutectic. The Ti-doped powders contain an additional phase with the TiAl 3 DO 22 crystal structure. However, quantitative analysis of the XRD results indicate a far greater fraction of the TiAl 3 phase is present than could be accounted for by a simple mass balance on Ti. This appears to be a (Ti x Ni 1-x )Al 3 phase in which higher cooling rates favour small x (low Ti-site occupancy by Ti atoms). SEM and EDX analysis reveal that virtually all the available Ti is contained within the TiAl 3 phase, with negligible Ti dissolved in either the Ni 2 Al 3 or NiAl 3 phases.

Microstructural development and mechanical properties of drop tube atomized Al-2.85 wt% Fe

“…The drop tube technique is a containerless solidification process which combines deep undercooling and high cooling rate under free-fall conditions, wherein buoyancy driven convection may be much reduced. Such containerless processing eliminates possible heterogeneous nucleation sites from mold/container walls, while the use of high vacuum or inert gas atmospheres within such equipment avoids oxidation, which also reduces the density of favourable sites for heterogeneous nucleation [16][17][18] . Moreover, drop tube processing provides a good analogue for commercial powder production techniques, such as high pressure gas atomisation (HPGA), and we might reasonably expect that microstructures observed in drop tube studies will be replicated in commercial HPGA powders of similar composition.…”

Bimodal NdNiAl and NdFeB hybrid catalytic and magnetic nanoparticles laminated on Fe foam: catalytic conversion of CO + 3H2 to CH4

“…[15][16][17][18][19] Compared to other noble or rare earth metals, Nd is an effective dopant from the aspect of its high catalysis and strong magnetism; although Pt, Ti, Ir, and Ru are commonly used as catalytic dopants in the synthesis of the NiAl RANEY® catalyst. [20][21][22][23][24][25][26] Meanwhile, magnetic NdFeB also has several superior properties that have mainly been exploited in electrochemical or magnetic devices. 23,27 This is primarily due to its excellent saturation magnetization and coercivity values.…”