Grant-in-Aid for General Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||Hokkaido University|
KIUCHI Hiromichi Hokkaido Univ., Fac. of Eng., Associate Professor, 工学部, 助教授 (90001247)
|Project Period (FY)
1989 – 1990
Completed(Fiscal Year 1990)
|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1990 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1989 : ¥1,700,000 (Direct Cost : ¥1,700,000)
|Keywords||Fine powder / Platinum / Palladium / Hydrogen reduction / Aqueous solution / Maturing / Kinetics / SEM observation / 貴金属塩水溶液 / 貴金属微粉末 / 塩化パラジウム酸水溶液 / パラジウム微粉末|
Chloro-platinum-acid solution was reduced by pressure hydrogen.
The reduction rate did not depend on the Pd concentration.
The dependency to reaction rate on hydrogen pressure was 1st order and the activation energy was 3.1 kcal/mol.
The rate determing step was the diffusion of dissolved hydrogen through the liquid film at the interface of hydrogen-solution or platinum-solution.
The spherical particles (about 1 um in diameter) were obtained under the conditions of low temperature, low hydrogen pressure, low reduction and high agitation, and could be estimated to be suitable for thick film.
The reaction rate increased with raising pH, but it decreased suddenly at 13 of pH showing the long induction period.
This behavior was broken off by heating the solution because OH^- ions coordinated strongly around Pt ion.
Chloro-palladium-acid solution was reduced under atmospheric hydrogen.
Data were very scattered, but the good reproducibility was obtained by pre-heating the solution.
The dependency of the reaction on the Pd concentration and the activation energy were zero order and 3.3 kcal/mol at the first stage of the reaction, and first order and 4.2 kcal/mol at the latter stage.
The reaction rate at the first stage showed 1st order dependency on hydrogen partial pressure. The rate was determined by the diffusion of dissolved hydrogen through the liquid film at Pd surface at the firts stage and by the Pd ion diffusion through the same film at the latter stage. The border depended on the concentration of Pd ions.
The particles were irregular shape, more smaller than Pt particles and apt to aggregate.
As the peak of X-ray diffraction of the particle at low reduction showed the broading, it was calculated that the particle was composed of 0.06 mum particles. The particles at high reduction began to aggregate and crystallize.