| A surface study of two unsupported nickel catalytic systems, Raney nickel and Urushibara nickel, was carried out by the use of electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX).; The surfaces of freshly polished Ni/Al (Raney nickel) alloys: Ni(,3)Al, NiAl, Ni(,2)Al(,3) and NiAl(,3) + eutectic were first studied to investigate the effect of the bulk composition on the surface. In all cases, aluminum was observed to segregate to the surface, the degree of segregation increased with the bulk concentraion of Al. The segregation can be predicted from the solid-liquid phase diagram of the Ni/Al system. The lack of quantitative agreement between theory and experiment is attributed to formation of intermetallic compounds and oxidation effects. NaOH preferentially leached the NiAl(,3) + eutectic and Ni(,2)Al(,3).; Mo promoted commercial Raney nickel alloys were analyzed by ESCA and AES before and after NaOH leaching. The results of the molybdenum doped alloys indicated that the oxide thickness decreases with increasing bulk concentration of Mo. The variation in concentration of surface species of the activated catalysts correlated with previous hydrogenation activity studies. It was determined longer times and higher temperatures of NaOH leaching exposed greater amounts of nickel on the Raney catalysts.; Modeled Urushibara precipitated nickel was analyzed by ESCA, AES, SEM and EDX. Two different reducing agents were used to precipitate the nickel, Zn and Al. The results showed the precipitated nickel is sandwiched between the metal reducing agent (Zn or Al) and an oxide coating of Zn or Al. High temperature preparation (100(DEGREES)C) afforded a thinner oxide protective layer and a more uniform precipitated nickel of smaller crystallite size.; Decomposition of Cu compounds in x-ray photoelectron spectrometers was addressed. Thermal radiative heating from the x-ray gun was found as the primary source of sample decomposition. Analysis of the variation of Cu LMM Auger intensities as a function of chemical state was also presented. |
