Toshifumi Ashida

Relation Between the Conditions of Preparation and the Polarization Characteristics of Spongy Raney Nickel Electrodes Used as Anodes for Fuel Cells

This paper reports on Spongy Raney nickel electrodes that were prepared from substrates of spongy nickel plate coated with aluminum. Influences of the temperature for alloying and the weight ratio of aluminum to nickel (Al/Ni) in the substrate on polarization characteristics were studied in connection with the alloy compositions formed, and the surface microstructure of the catalysts. For this, the ratio Al/Ni in the substrate was varied ranging from 0.1 to 2.5. Electrode performance was improved, with increases in both the temperature for alloying and the Al/Ni ratio of the substrates. However, the higher the temperature used for alloying, the lower were the effects of the Al/Ni ratio. The activated Raney nickel was prepared from an alloy whose components were NiAl{sub 3} and/or Ni{sub 2}Al{sub 3}. It was also shown that a good polarization performance resulted from the increase in activated nickel grains, which were observed by scanning electron microscopy, and in increase in the Brunauer, Emmett, and Teller (BET) surface area of the electrode-catalyst. The broad peaks observed in x-ray diffraction of Raney nickel catalysts implied crystal distortions, which should be closely related to an increase in the BET surface area.

Spectroscopic study on plate- and sponge-type Raney nickel electrodes for fuel cells

Sponge-Type Raney Nickel Catalysts Were Used As Anodes In Liquid Fuel Cells Utilizing Methanol Or Hydrazine. Raney Nickel Electrodes Were Prepared From Substrates Of Spongy Nickel Plates Coated With Aluminium By Use Of A Plasma Flame Gun. Electrode Performance In Both Methanol And Hydrazine Fuel Cells Was Improved With Increases In Both The Alloying And The Electrolyte Temperature. Good Polarization Characteristics Resulted From An Increase In Activated Nickel Grains, Which Were Observed By Sem, And From An Increase In Bet Surface Area Of The Electrode. The Broad Peaks Observed In X-Ray Diffraction Of Raney Nickel Implied Crystal Distortion, Which Should Be Related To An Increase In Surface Area. Surface Chemical Specification And Distribution Of Aluminium And Nickel In The Plate-Type Raney Nickel Catalyst Based On Xps, Shows That The Catalyst Surface Is Covered With Ni2O3 And/Or Ni(Oh)2 Within 200 A Of The Surface, While L2O3 And/Or Al(Oh)3 Are Distributed Evenly In The Vertical Direction Over About 1200 A. The Xanes Spectrum From The Ni K-Edge Of The Raney Nickel Did Not Change Much From That Of Nickel Metal. The Exafs Function, However, Diminished More Quickly, And From This, The Coordination Number Of Nickel In Raney Nickel Catalysts Was Estimated To Be 6, Compared With 12 For Ordinary Nickel. This Indicates That The Other Six Nickel Atoms Shift From The Original Sites. Exafs Studies As Well As Xrd, Indicate That The Crystal Structure Of The Activated Nickel Contains A Great Number Of Crystal Defects. Epr Measurements Indicate The G-Values Of The Active Raney Nickel Catalyst And The Catalyst When Deactivated By Electrochemical Removal Of Hydrogen To Be 2.07 And 2.22 Respectively. The Change Of G-Value Is Attributed Not To The Lattice Defects But To The Adsorption Of Hydrogen.

Hydrothermal synthesis of calcium silicate briquettes from waste silica and lime, and their properties. Effects of alkali on hydrothermal synthesis and properties.

Waste silica with 5.6μm mean particle diameter was mixed with lime and autoclaved in alkaline solutions at 180°C for several hours under saturated vapor pressure. The observation under a scanning electron microscope (SEM), DTA and X-ray analysis were performed to determine the microstructure, phase component and crystallinity of the reaction products.The additions of sodium and potassium hydroxides accelerated the hydrothermal reaction. On the contrary, lithium hydroxide served as an inhibitor, because of the formation of Li2SiO3 on the surface of silica. Glauconite (mica group), an impurity in waste silica, retarded the crystal growth of calcium silicate hydrate, because of the formation of analcite (zeolite group) by sodium hydroxide.The use of low concentration of NaOH or KOH resulted not only in a considerable reduction in autoclaving time, but also in increasing the bending strength of calcium silicate hydrate briquettes. The addition of 1 wt% potassium titanate whisker (K2O·6TiO2) into the waste silica and lime caused the bending strength of briquettes to increase by about 40%.