The effect of catalyst and heat treatment on the properties of carbon-metal composites

摘要

Carbon gel and carbon-nickel-palladium doped gels (C-Ni-Pd) were prepared by carbonising resorcinol-formaldehyde (RF) hydrogel and resorcinol-formaldehyde-nickel-palladium (RF-Ni-Pd) hydrogels at 900 A degrees C in a nitrogen atmosphere. RF and RF-Ni-Pd hydrogels were synthesized through sol-gel polycondensation followed by ambient drying. The aim of this study was the determination of the effect of heat treatment in air at 450 A degrees C on the properties of C-Ni-Pd gels prepared using different Pd salts. In the present work, Ni was added as acetate whereas Pd was added as acetate (CA-Ni-Pd) and as chloride (CB-Ni-Pd). Samples were examined by scanning electron microscopy and X-ray diffraction. Surface area was characterized by N-2 adsorption at -195.5 A degrees C. Thermogravimetric analysis was carried out in order to determine the thermal characteristics of carbon gel and nickel-palladium composites in air atmosphere. CA-Ni-Pd composite had a higher activity and two-phase reaction compared to the CB-Ni-Pd composite. Further improvement of the electrolyte diffusion into the particles of nickel and palladium was obtained by oxidative thermal treatment. During this process a structural modification of the material took place, consequently leading to changes in the electrochemical properties of the composites.