LOCAL STRUCTURE CHARACTERIZATION OF GADOLINIUM DOPED AMORPHOUS AND CRYSTALLINE ALUMINA

2001 ◽  
Vol 15 (12n13) ◽  
pp. 375-384 ◽  
Author(s):  
S. SIMON
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Local Structure ◽  
Sol Gel ◽  
Structure Characterization ◽  
Epr Spectra ◽  
Paramagnetic Resonance ◽  
Amorphous Alumina ◽  
Electron Paramagnetic ◽  
Crystalline Alumina

The evolution of local structure during the transition from amorphous to crystalline states of gadolinium doped alumina is characterized by electron paramagnetic resonance (EPR). The EPR spectra of samples belonging to the (1 - x) Al 2 O 3x Gd 2 O 3 system, where x = 0.002, 0.01, 0.05 and 0.1, show that the gadolinium ions are relatively uniformly distributed in amorphous alumina granules prepared by sol–gel methods. First, gadolinium doped α-alumina appears on the surface of the γ-alumina granules where there are low coordinated (N < 6) gadolinium species. The transition from γ- to α-alumina is postponed by the presence of high coordinated gadolinium (N < 6) ions inside of γ-alumina granules.

Characterization of titanium dopants in sodium alanate by electron paramagnetic resonance spectroscopy

2005 ◽  
Vol 20 (12) ◽  
pp. 3265-3269 ◽  
Author(s):  
Meredith T. Kuba ◽  
Sandra S. Eaton ◽  
Christine Morales ◽  
Craig M. Jensen
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Epr Spectra ◽  
Minor Amount ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Dehydrogenation Kinetics ◽  
Electron Paramagnetic ◽  
Kinetics Of

Electron paramagnetic resonance (EPR) spectra were obtained for samples of Ti-doped NaAlH4 subjected to different numbers of cycles of dehydrogenation/re-hydrogenation. Ti is observed to evolve from its initial Ti(III) state through a series of Ti(0) species during the first 5 cycles. Although the conversion of Ti(III) to Ti(0) occurs much more readily for TiCl3-doped samples than those prepared with TiF3, in both cases the evolution of Ti follows the same sequence that involves 3 distinguishable Ti(0) species and ends in the predominance of the same single Ti(0) species. The spectrum of a sample of NaAlH4 containing 2 mol% of cubic Al3Ti is distinctly different than any of those observed for the Ti(0) species that arise during the hydrogen cycling of the hydride. The major changes in the nature of the predominant Ti species have little if any effect on the dehydrogenation kinetics, which strongly suggests that the profoundly enhanced hydrogen cycling kinetics of Ti-doped NaAlH4 are due to a Ti species present in only a relatively minor amount.

scholarly journals Magnetic characterization of microcrystalline Na3Ln0.99–xEr0.01Crx(PO4)2 orthophosphates synthesized by Pechini method (Ln = La, Gd)

2018 ◽  
Vol 35 (4) ◽  
pp. 733-745 ◽  
Author(s):  
S.M. Kaczmarek ◽  
G. Leniec ◽  
H. Fuks ◽  
T. Skibiński ◽  
A. Pelczarska ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Magnetic Susceptibility ◽  
Low Temperature ◽  
Pechini Method ◽  
Epr Spectra ◽  
Magnetic Characterization ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Co Doped

Abstract Na3Ln(PO4)2 orthophosphates (Ln = La, Gd) doped with Er3+ and co-doped with Cr3+ ions were synthesized by Pechini method and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Low temperature EPR spectra were detected and analyzed in terms of temperature dependence and the structure of the obtained materials. They show that erbium and chromium ions substitute Ln3+ and also Na+ ions or Na+ channels forming complex EPR spectra. Both kinds of ions reveal ferromagnetic type of interaction which shows some anomaly at the temperature between 10 K and 15 K. Magnetic susceptibility reveals a weak antiferromagnetic kind of interaction dominating in the whole temperature range, from 3.5 to 300 K.

Electron Paramagnetic Resonance of Radicals Formed during Milling

1960 ◽  
Vol 33 (2) ◽  
pp. 462-468 ◽  
Author(s):  
S. E. Bresler ◽  
S. N. Zhurkov ◽  
E. N. Kazbekov ◽  
E. M. Saminskiĭ ◽  
E. E. Tomashevskiĭ
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Gamma Rays ◽  
Epr Spectra ◽  
Mechanical Degradation ◽  
Present Communication ◽  
Surface Layers ◽  
Paramagnetic Resonance ◽  
Mechanical Destruction ◽  
Electron Paramagnetic

Abstract It is well known that during the mechanical degradation of polymers there takes place scission of molecular chains and the formation of macroradicals. It is of considerable interest to study the electron paramagnetic resonance (EPR) spectra of the macroradicals produced by milling, and to compare them with the spectra of the macroradicals formed in the process of polymerization, and also during the irradiation of polymers by gamma rays and neutrons. We may endeavor to compare the amount of macroradicals formed with the extent of mechanical destruction (for instance with the area of the new interface which is formed). In addition, as was found by experience, the macroradicals formed by mechanical scission are good models for the investigation of reactivity since practically all of them are in the newly formed surface layers and are therefore very accessible to various chemical influences. They enter easily into reaction with various agents present in the medium since in this process diffusion from the surface is found in practice not to be a predominating factor. In the present communication we give the first EPR results obtained on mechanically degraded polymers.

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