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1

The Evidence of Quasi-Free Positronium State in GiPS-AMOC Spectra of Glycerol

100%

Zvezhinskiy D., Butterling M., Wagner A., Krause-Rehberg R., Stepanov S.

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vol. 125

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issue 3

821-824

EN

We present the results of processing of age-momentum correlation spectra that were measured for glycerol by the gamma-induced positron spectroscopy facility. Our research has shown that the shape of experimental s(t) curve cannot be explained without introduction of the intermediate state of positronium (Ps), called quasi-free Ps. This state yields the wide Doppler line near zero lifetimes. We discuss the possible properties of this intermediate Ps state from the viewpoint of developed model. The amount of annihilation events produced by quasi-free Ps is estimated to be less than 5% of total annihilations. In the proposed model, quasi-free Ps serves as a precursor for trapped Ps of para- and ortho-states.

2

Compensation Models in Chlorine Doped CdTe Based on Positron Annihilation and Photoluminescence Spectroscopy

73%

Stadler W., Hofmann D. M., Meyer B. K., Krause-Rehberg R., Polity A., Abgarjan T., Salk M., Benz K. W., Azoulay M.

Acta Physica Polonica A

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1995

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vol. 88

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issue 5

921-924

EN

In this investigation positron annihilation, photoluminescence and electron paramagnetic resonance techniques are employed to gain insight in the compensation of CdTe doped with the halogen Cl. We will demonstrate that the high resistivity of CdTe:Cl cannot be explained by the interaction between the shallow effective mass type donor Cl on Te site and the doping induced shallow acceptor complex, a Cd vacancy paired off with a nearest-neighbour Cl atom (A centre). From electron paramagnetic resonance investigations we conclude that the mid gap trap, often detected by electrical methods in CdTe, is not the isolated Cd vacancy.

3

Multicomponent (Ti-Zr-Hf-V-Nb)N Nanostructure Coatings Fabrication, High Hardness and Wear Resistance

73%

Pogrebnjak A., Beresnev V., Kolesnikov D., Bondar O., Takeda Y., Oyoshi K., Kaverin M., Sobol O., Krause-Rehberg R., Karwat C.

Acta Physica Polonica A

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2013

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vol. 123

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issue 5

816-818

EN

First results in the field of synthesis and research of the multicomponent (Ti-Zr-Hf-V-Nb)N nanostructured coatings are presented in the paper. Influence of processes of spinodal segregation and mass-transfer on single-layered or multilayered crystal boundary (second phase) forming were explored. Superhard nanostructured coatings were investigated before and after annealing at the temperature 600°C using unique methods (slow positron beam, proton microbeam particle induced X-ray emission-μ, Rutherford backscattering-analysis, scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction analysis was performed using DRON-4 and nanoindentor). Diffraction spectra were taken point-by-point, with a scanning step 2Θp=0.05 to 0.1°. We detected that positron trapping by defects was observed on the nanograins boundaries and interfaces (vacancies and nanopores which are the part of triple and larger grain's boundary junction). The 3D distribution maps of elements obtained by the proton microbeam (particle induced X-ray emission-μ) together with the results obtained by slow positron microbeam gave us comprehensive information about physical basis of the processes, connected with diffusion and spinodal segregation in superhard coatings.

4

Influence of Deposition Parameters and Thermal Annealing on the Structure and Properties of Nitride Coatings (TiHfZrVNb)N

73%

Pogrebnjak A., Abadias G., Chartier P., Bondar O., Yakuschenko I., Takeda Y., Krause-Rehberg R., Kolesnikov D., Beresnev V., Partyka J.

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vol. 125

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issue 6

1296-1299

EN

Results of structure, phase composition, physical and mechanical properties and tribological properties investigations of nitride high-entropy coatings (TiZrHfVNb)N are presented in the paper. Proton microbeam (μ-PIXE), X-ray diffraction method, including method of X-ray strains measurements, energy dispersive X-ray spectroscopy and scanning electron microscopy analysis, microhardness testing and nanoindentation were used. Thermal annealing (t=600°C) influence on defect profiles, structure and element distribution in the coatings was investigated. It was found that thermal treatment of coatings leads to changing of defect profiles and to element redistribution. Also we can say that it influences less on grain size changing. Investigated (TiZrHfVNb)N coatings demonstrate high values of hardness and excellent wear resistance.

5

The Temperature and Pressure Dependence of the Free Volume in Fluoroelastomers from PALS and PVT Experiments

73%

Dlubek G., Sen Gupta A., Wawryszczuk J., Kilburn D., Pionteck J., Krause-Rehberg R., Goworek T., Alam M., Kaspar H., Lochhaas K.

Acta Physica Polonica A

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2005

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vol. 107

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issue 4

685-689

EN

Positron lifetime and pressure-volume-temperature experiments were performed as function of T (100-485 K) and P (10^{-5} Pa-500 MPa) on a fluoroelastomer. From positron annihilation lifetime spectroscopy, analyzed with LT9.0 assuming a dispersion in the e^+ (τ_2) and o-Ps (τ_3) lifetime, the mean, 〈v_h〉, and the width (standard deviation), σ_h, of the hole size distribution were calculated. The pressure-volume-temperature data were analyzed using the Simha-Somcynsky hole-lattice theory to estimate the specific hole free volume V_f. From a comparison of V_f with 〈v_h〉 the specific hole number, N'_h, is estimated. The data from thermal expansion and pressure experiments show complete agreement when taking into account the compressibility of the occupied volume.

Refine search results

The Evidence of Quasi-Free Positronium State in GiPS-AMOC Spectra of Glycerol

Compensation Models in Chlorine Doped CdTe Based on Positron Annihilation and Photoluminescence Spectroscopy

Multicomponent (Ti-Zr-Hf-V-Nb)N Nanostructure Coatings Fabrication, High Hardness and Wear Resistance

Influence of Deposition Parameters and Thermal Annealing on the Structure and Properties of Nitride Coatings (TiHfZrVNb)N

The Temperature and Pressure Dependence of the Free Volume in Fluoroelastomers from PALS and PVT Experiments