| | 1 | Author
| J. M. Ramallo-López, F. G. Requejo, A. G. Bibiloni, M. Rentería, L. Gutierrez, E. E. Miró | Requires cookie* | | | Title
| Combined TDPAC and EXAFS Study of InPt/FER Catalysts  | | | | Abstract
| Time Differential Perturbed Angular Correlation (TDPAC) experiments using 111 In as probe were performed in order to determine the nature of In-sites in In-ferrierite (In/FER), before and after the incorporation of Pt through the hyperfine interaction between the nuclear quadrupole moment of the probe's nucleus and the extranuclear electric field gradient (EFG). Extended X-ray Absorption Fine Structure (EXAFS) measurements were performed to measure the absorbance above the Pt's L m absorption edge in the transmission mode in order to determine the local environment of Pt atoms in Pt/FER and InPt/FER catalysts. TDPAC spectra of 111 In in In/FER and InPt/FER taken at 500°C in air indicated that there are no changes in the indium surroundings after the incorporation of Pt. Three sites were found for indium in both samples. Two of them correspond to the two sites of indium in ln 2 0 3 and the third one is attributed to In in exchange sites of the zeolites. Their population, quadrupole frequencies and asymmetry parameters didn't change with the incorporation of Pt. EXAFS experiments showed similar near neighborhood Pt-0 distances and Pt coordination number in Pt/FER and InPt/FER samples. There is no evidence of the presence of any In-Pt bimetallic entity in InPt/FER catalyst. | | | |
Reference
| Z. Naturforsch. 55a, 327—330 (2000); received August 26 1999 | | | |
Published
| 2000 | | | |
Keywords
| Hyperfine Interactions, TDPAC, EXAFS, Catalysis, Ferrierite | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0327.pdf | | | | Identifier
| ZNA-2000-55a-0327 | | | | Volume
| 55 | |
| 2 | Author
| P. Wodniecki, B. Wodniecka, M. Marszalek, A. Z. Hrynkiewicz | Requires cookie* | | | Title
| PAC Studies of Ag-Hf Intermetallic Compounds | | | | Abstract
| The hyperfine quadrupole interaction of 181 Ta and 111 Cd probes in HfAg and HfiAg com-pounds was studied at 24 to 1100 K with the time -differential perturbed angular correlation (TDPAC) technique. The EFGs measured in HfAg on 181 Ta and m Cd are 1.388(5)x 10 18 VcnT 2 and 0.340(5)x 10 lx Vcm -2 , respectively. For both probe atoms a linear decrease of the EFG with temperature was observed with slopes 1.1 l(2)x 10 -4 KT 1 and 1.73(5)x 10~ 4 KT 1 for 181 Ta and "'Cd, respectively. In Hf 2 Ag, 0.469(2)x 10 18 VcnT 2 was determined on 181 Ta nuclei and 0.428(5)x 10 18 Vcm -2 on '"Cd. Also a linear EFG temperature dependence with the large slope of 2.39(6)x 10 -4 K" 1 was observed for "'Cd probes in Hf 2 Ag, while the EFG measured on l8l Ta nuclei in this compound exhibits a very weak temperature variation which can be fitted neither with a linear T nor a T ?/2 dependence. In all cases the electronic contributions to the EFG are very small indicating that these transition element systems do not obey the universal correlation between the electronic and the ionic EFG observed in numerous other systems not belonging to the transition metal series. | | | |
Reference
| Z. Naturforsch. 51a, 437—441 (1996); received November 20 1995 | | | |
Published
| 1996 | | | |
Keywords
| Hyperfine interactions, perturbed angular correlations, electric field gradient, inter-metallic compounds, Ag-Hf system | | | |
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| default:Reihe_A/51/ZNA-1996-51a-0437.pdf | | | | Identifier
| ZNA-1996-51a-0437 | | | | Volume
| 51 | |
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