Use of Fe3+ ion probe to study the stability of urea-intercalated kaolinite by electron paramagnetic resonance

2007 ◽  
Vol 313 (2) ◽  
pp. 537-541 ◽  
Author(s):  
Cristiane Regina Budziak Fukamachi ◽  
Fernando Wypych ◽  
Antonio Salvio Mangrich
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Resonance ◽  
Ion Probe ◽  
The Stability ◽  
Electron Paramagnetic

Intrinsic Defects in HPSI 6H-SiC: an EPR Study

2008 ◽  
Vol 600-603 ◽  
pp. 381-384 ◽  
Author(s):  
Patrick Carlsson ◽  
Nguyen Tien Son ◽  
Björn Magnusson ◽  
Anne Henry ◽  
Erik Janzén
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Vapor Deposition ◽  
Thermal Activation ◽  
Chemical Vapor ◽  
Paramagnetic Resonance ◽  
Intrinsic Defects ◽  
Annealing Behavior ◽  
Carbon Vacancy ◽  
The Stability ◽  
Electron Paramagnetic

High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects. The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV above the valence band. The thermal activation energies as determined from the temperature dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of the intrinsic defects and the stability of the SI properties were studied up to 1600°C.

The stoichiometry and stability of the NADP complexes with manganese(II) ions as studied by electron paramagnetic resonance

1979 ◽  
Vol 57 (7) ◽  
pp. 995-999
Author(s):  
M. Kirk Green ◽  
George Kotowycz
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Stability Constant ◽  
Metal Ion ◽  
Metal Ion Binding ◽  
Paramagnetic Resonance ◽  
Ion Concentrations ◽  
Ion Binding Sites ◽  
The Stability ◽  
Electron Paramagnetic ◽  
Apparent Stability

Magnetic resonance techniques have been applied to study the stability of the complexes formed between Mn(II) ions and NADP in aqueous solutions at a pH of 7.5 and 20 °C. The electron paramagnetic resonance (epr) data indicate that at low Mn(II) ion concentrations ([Mn(II)] < 1 mM; [NADP] ~ 5 mM), a 1:1 complex is formed with an apparent stability constant K1 = 370 ± 50 M−1 at an ionic strength of 0.22 in the presence of 0.20 M Cl−. At high Mn(II) ion concentrations, a Mn(II)2 –NADP species, with an apparent stability constant K2 = 54 ± 17 M−1, is present in significant amounts. When the epr data are corrected for the presence of the MnCl+ ion, the analysis of the new Scatchard plot yields stability constants for the two sites of K1 = 640 ± 90 M−1 and K2 = 88 ± 13 M−1 respectively. The presence of two metal ion binding sites on the NADP molecule has not been observed previously, and previous workers have always analyzed their data in terms of the 1:1 Mn(II)–NADP complex. An epr temperature study of K1 yields a value of ΔH equal to 1.3 ± 0.2 kcal/mol (1 cal = 4.187 J).

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