| Title |
Influence of the Water Vapor Content on the Hydrogen Reduction Process of Nanocrystalline NiO |
| Authors |
(Sung Soo Jung); (Hyo Sang An); (Jai Sung Lee) |
| DOI |
https://doi.org/10.3365/KJMM.2010.48.04.315 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
NiO; nanostructured materials; H2 reduction; powder processing; thermodynamic properties |
| Abstract |
In this study, the hydrogen reduction behavior of ball-milled NiO nanopowder was investigated depending on the partial pressure of water vapor. The hydrogen reduction behavior was analyzed by thermogravimetry and hygrometry under heating to 873 K in hydrogen. In order to change the partial pressure of the water vapor, the dew point of hydrogen was controlled in the range of 248 K~293 K by passing high-purity hydrogen through a saturator that contained water. Interestingly, with the increase in the dew point of the hydrogen atmosphere, the first step of thehydrogen reduction process decreased and the second step gradually increased. After the first step, apore volume analysis revealed that the pore size distribution in the condition with ahigher water vapor pressure shifted to a larger size, whereasthe opposite appearedat a lower pressure. Thus, it was found that the decrease in the pore volume during the chemical reaction controlled process at a dew point of 248 K caused a reduction in retardation in the diffusion controlled process. (Received November 18, 2009) |