An enhancement of catalytic activities for ammonia decomposition was achieved using partial doping of Sr, Y, Zr, or Ce in Al 2 O 3 frameworks. Improvements of the catalytic properties, including Ni dispersion, acidic sites, and basic sites have been studied. In this study, the Ni/doped Al 2 O 3 catalysts exhibit a great improvement of Ni dispersion, which results in higher catalytic activities, relative to Ni/undoped Al 2 O 3 . Among the studied catalysts, Ni/Ce-doped Al 2 O 3 exhibits the highest NH 3 conversion, and Ni/Y-doped Al 2 O 3 exhibits the best catalytic stability. The results of N 2 formation from NH 3 -TPRx imply that the recombination of nitrogen in the NH 3 decomposition mechanism could be the rate-determining step in this study. Decomposition of NH 3 from urine was further evaluated over active Ni/Ce-doped Al 2 O 3 . The catalyst can produce H 2 in the range of 169-188 μmol⋅min -1 ⋅g cat -1 with 72.1% NH 3 conversion. The role of dopants in the Al 2 O 3 frameworks for the catalytic activities was also discussed, to understand the NH 3 decomposition mechanism.

No abstract

Catalytic activity of Ni catalysts for NH3 decomposition can be enhanced by using Ce‐doped Al2O3 support. Magnetic inducement during sol‐gel preparation of supports was studied to enhance the Ce dispersion in Al2O3 framework. In this study, the same poles and different pole of magnetic arrangement were applied during the sol‐gel preparation. Ni catalysts over the supports were investigated for the NH3 decomposition activity along with catalyst and support properties, including Ce dispersion in Al2O3 framework, Ni dispersion, acidic sites, basic sites, and reaction kinetics. The magnetic inducement can control the Ce composition and uniformity in the Al2O3 framework. The Ni/Ce‐doped Al2O3 prepared under the same poles of magnetic inducement show significant improvements in Ni dispersion, and yield highest catalytic activity due to a high Ce composition and uniformity in the framework, as well as the high Lewis basic sites which enhance the limiting step of NH3 decomposition. Thus, combination of the partial doping with magnetic inducement provides a novel approach with low cost to improve the activity of Ni catalyst without changing the reaction mechanism.

The present studies investigate the wear response of composition-modulated multilayer Ni-W coatings as fabricated by electrodeposition. By regulating the pulse waveforms of the applied currents, the chemical composition, grain size, and the individual layer thickness of the electrodeposited Ni-W CMMC can be tailored. The ball-on-disc test and the subsequent microstructural analysis indicates that the wear resistance and friction coefficient of Ni-W CMMC are influenced by the composition and the thickness of the individual alternating layer. The decrement of interlayer’s size monotoically increase wear resistance and friction coefficient.

No abstract