Wyniki wyszukiwania - Biblioteka Nauki

Ten serwis zostanie wyłączony 2025-02-11.

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 4

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Characterisation of amorphous state of REE2Fe2+Be2Si2O10 by spectroscopic methods.

100%

Malczewski D. , Skrzypek D. , Molak A.

Archives of Materials Science

2004

tom Vol. 25, nr 4

561-571

This paper presents 57Fe Moessbauer spectroscopy, electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), X-ray diffraction (XRD), gamma-ray spectroscopy and dielectric permitivity spectroscopy studies of fully metamict gadolinite REE2Fe2+Be2Si2O10 from Ytterby (Sweden). X-ray and electron diffraction patterns of the sample show complete lack of long range order (LRO). 57Fe Moessbauer spectroscopy of the sample revealed only Fe3+ ions definitely located in octahedral coordinations, similar to thye crystalline structure of gadolinite. The EPR resonance spectrum is complete and its features corespond to Gd3+ and Mn2+ centers. The Gd3+ centers show low-symmetry of local crystal field and may be characterized by distribution of spin-Hamiltonian parameters such as: g-factor and fine-structure parameters. The temperature dependence of utensity proves that a fraction of gadolinium ions interact by superexchange type mechanism and reveals that these exchange interactions are of the antiferromagnetic type Mn2+ centers and the character of Mn2+ EPR spectra indicate that this spectra are atributed to isolated manganium ions. The AC conductivity exhibits thermally activated behavior above 420 K whereas the dielectric constant shows a step-like anomaly near 230 K.

The Characterization of Modified Higher Aliphatic Alcohols-Synthesis Catalysts by EPR and XPS Methods

100%

Skrzypek D. , Krupa K. , Winiarski A. , Szymanska B.

2005

tom Vol. 79 / nr 1

145-153

Aseries of copper-zinc catalysts for aliphatic alcohols synthesis with a varying amount of additives was prepared by thermal decomposition of metal citrates. The results of catalytic experiments, made in a laboratory high-pressure reactor, showed a good stability and almost constant activity and selectivity during 4 months. In this paper the catalyst before (A) and after (B) reaction is characterized by EPR and X-ray photoelectron spectroscopies. For catalystAthe copper species were identified as isolated Cu2+ ions in a dynamic Jahn-Teller configuration. For the sample B the EPR spectrum is complex and its features are corresponding to: clustered Cu2+ species with dipole-dipole interaction; Fe3+ ions in rhombically distorted symmetry; O2- centres.

The Synthesis and Spectroscopic Study of Novel Binuclear Chromium(III) Complex with Pipemidic Acid

88%

Skrzypek D. , Kovala-Demertzi D. , Szymanska-Niewiadomska B. , Kourkoumelis N. , Staninska M.

2009

tom Vol. 83, nr 3

363-371

The interaction of Cr(III) with pipemidic acid, Hpipem, afforded the complex [Cr(pipem)(HO)2(H2O)]2 Cr2O3. The new complex has been characterized by elemental analysis, infrared, XRD and EPR spectroscopy. The EPR spectra of the complex have been recorded down to T = 3 K. The temperature dependence of EPR spectrum demonstrates that spectrum originates from septet transitions at a room temperature and from quintet state for lower temperatures for exchange coupled chromium pairs. The dimer characterizes antiferromagnetic interaction with J = -32 cm-1. The monoanion, pipem, exhibits obligation through the carbonyl and carboxylatooxygen atoms. Six-coordinate dimer distorted octahedral configuration has been proposed for [Cr(pipem)(HO)2(H2O)]2.

Seasonal variation in the chemical composition and morphology of aerosol particles in the centre of Katowice, Poland

75%

Wawros A. , Talik E. , Zelechower M. , Pastuszka J. S. , Skrzypek D. , Ujma Z.

Polish Journal of Environmental Studies

2003

tom 12

nr 5

PM-2.5 and PM-10 samples were collected in the centre of Katowice, Poland during February to May 2001. They were analyzed by gravimetry, X-ray photoelectron spectroscopy and scanning electron microscopy combined with an energy dispersive spectrometer and electron paramagnetic resonance. The combination of these methods allows us to analyze elemental composition, size and morphology of more than three hundred individual atmospheric particles. The composition of the aerosol particles is strongly influenced by meteorological conditions such as wind speed and direction. Mineral elements mainly existed in large-size particles. The anthropogenic pollution elements, however, are contained in corpuscles (< 2 ^m). In comparison with the situation in the wintertime, the number of particles rich in some heavy metals in springtime was found to be lower. The EPR spectra are complex and their features correspond to: I type: Cu2+ centra in a low-symmetry host site, II type: radical species in the soot, which appears as the paramagnetic pyrolyzed product.