Temat: 78.70.-g - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Magnetron Sputtered SnO$\text{}_{x}$ Films on Tin Probed by Slow Positron Implantation Spectroscopy
Autorzy:: Nancheva, N.
Docheva, P.
Anwand, W.
Brauer, G.
Coleman, P. G.
Tematy:: 78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2008107.pdf Link otwiera się w nowym oknie
Opis:: SnO$\text{}_{x}$ films grown on tin substrates via d.c. magnetron sputtering at different bias were studied by slow positron implantation spectroscopy. The change of substrate bias from -40 V to -140 V and its influence on the films is shown and discussed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Positron Implantation Profile in Kapton
Autorzy:: Dryzek, J.
Dryzek, E.
Tematy:: 78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2047124.pdf Link otwiera się w nowym oknie
Opis:: The discussion presented in the paper focuses on processes accompanying positron implantation in condensed matter. They finally constitute the positron implantation profile which generally does not exhibit the exponential behavior as it is concluded from the Monte Carlo simulation made using the EGSnrc 4.0 code. The simulation was performed for the kapton and two commonly used positron sources $\text{}^{22}$Na and $\text{}^{68}$Ge/g$\text{}^{68}$Ga. New formula for the implantation profile was proposed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Chemical Effects on the K$\text{}_{β}$/K$\text{}_{α}$ Intensity Ratios in First-Row Transition Element Compounds
Autorzy:: Küçükönder, A.
Büyükkasap, E.
Yilmaz, R.
Şahin, Y.
Tematy:: 78.70.-g
82.80.-d; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1994736.pdf Link otwiera się w nowym oknie
Opis:: Chemical Effects on the K$\text{}_{β}$/K$\text{}_{α}$ X-ray Intensity Ratios for Some First-row Transition Element Compounds Were Studied Experimentally and Calculated. the Vacancies in the K Shell Were Created by 59.5 keV γ rays from an $\text{}^{241}$Am Radioactive Source and Characteristic X-ray Radiation from Sample Was Measured by Using Si(li) and Ge(li) Detectors. the Calculations Were Carried Out Using Brunner's Model. the Calculated Relative K$\text{}_{β}$/K$\text{}_{α}$ X-ray Intensity Ratios Are in Good Agreement with the Present and the Previously Published Experimental Data.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: The Temperature and Pressure Dependence of the Free Volume in Fluoroelastomers from PALS and PVT Experiments
Autorzy:: Dlubek, G.
Sen Gupta, A.
Wawryszczuk, J.
Kilburn, D.
Pionteck, J.
Krause-Rehberg, R.
Goworek, T.
Alam, M. A.
Kaspar, H.
Lochhaas, K. H.
Tematy:: 61.41.+e
78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2042202.pdf Link otwiera się w nowym oknie
Opis:: Positron lifetime and pressure-volume-temperature experiments were performed as function of T (100-485 K) and P (10$\text{}^{-5}$ Pa-500 MPa) on a fluoroelastomer. From positron annihilation lifetime spectroscopy, analyzed with LT9.0 assuming a dispersion in the e$\text{}^{+}$ (τ$\text{}_{2}$) and o-Ps (τ$\text{}_{3}$) lifetime, the mean, 〈v$\text{}_{h}$〉, and the width (standard deviation), σ$\text{}_{h}$, 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$\text{}_{f}$. From a comparison of V$\text{}_{f}$ with 〈v$\text{}_{h}$〉 the specific hole number, N'$\text{}_{h}$, is estimated. The data from thermal expansion and pressure experiments show complete agreement when taking into account the compressibility of the occupied volume.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: A Simplified Method for the Estimation of Hole Free Volume Fraction from the Specific Volume
Autorzy:: Dlubek, G.
Pionteck, J.
Tematy:: 61.41.+e
78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1812487.pdf Link otwiera się w nowym oknie
Opis:: A brief introduction in the equation of state of the Simha-Somcynsky hole theory is presented. This theory allows to calculate the volume fraction h of free volume holes from pressure-volume-temperature experiments. These holes are detected by ortho-positronium and from the value of h and the mean ortho-positronium hole size the hole density may be calculated. We discuss a simplified method to estimate h which makes use of the relation V* = 1.52 $V_W$ between the scaling volume V* of the Simha-Somcynsky hole theory equation of state and the van der Waals volume $V_W$. Moreover, we present a new simplified method for the estimation of h which starts with the Schottky (Arrhenius) equation for the concentration of thermal vacancies and makes use of a linear relation between the scaling temperature T* and the hole formation enthalpy $H_h$, $H_h$(kJ/mol)=6.54×$10^{-4}$T*(K).
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 6.

Tytuł:: Partial Probabilities of X-Ray Bremsstrahlung Transitions
Autorzy:: Nietubyć, R.
Sobczak, E.
S̆imůnek, A.
Vackár̆, J.
S̆ipr, O.
Tematy:: 79.20.Kz
78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1963394.pdf Link otwiera się w nowym oknie
Opis:: High-energy electrons bombarding a solid produce X-ray bremsstrahlung radiation, which is one of few elementary processes occurring during electron-solid interactions. Photon emission results from electron transition to an unoccupied electron state above the Fermi level. In this work matrix elements of X-ray bremsstrahlung transitions were calculated for solids containing elements from N (Z=7) to Pd (Z=46) and photon energies 1487 eV and 5415 eV. It was found that in the case of light elements the X-ray bremsstrahlung transitions to s-type final states dominate over all other symmetries. It was also shown that X-ray bremsstrahlung transition probabilities increase with decreasing photon energy and increasing atomic number Z. Dependence of X-ray bremsstrahlung transition probabilities on the electron final state energy is also presented in this work.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 7.

Tytuł:: Relations Between Hole Volume and Macroscopic Volume in Various Polymers
Autorzy:: Dlubek, G.
Alam, M. A.
Saarinen, K.
Stejny, J.
Fretwell, H. M.
Tematy:: 61.41.+e
65.70.+y
78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2007964.pdf Link otwiera się w nowym oknie
Opis:: Different definitions of the free volumes are discussed and related to the total specific volume and to the local free (hole) volume. Positron lifetime measurements are reported for polyethylene, polytetrafluoroethylene, and CR39-copolymers. Two long-lived components appear in polyethylene and polytetrafluoroethylene, which were attributed to o-Ps annihilations in crystalline regions and in holes of the amorphous phase. From a relation between the coefficients of the thermal expansion of macroscopic and hole volume, the fractional hole volume h and from this the number of holes, N, is estimated. Values of T$\text{}_{g}$=195 K, h$\text{}_{g}$=4.5% (polyethylene) and 5.7% (polytetrafluoroethylene) and N$\text{}_{g}$=0.73 nm$\text{}^{-3}$ (polyethylene) and 0.36 nm$\text{}^{-3}$ (polytetrafluoroethylene) were obtained. In semicrystalline polymers these values agree with estimates obtained from the densities of the crystalline and amorphous phases. The effect of cross-linking on the free-volume properties of CR39-copolymer networks was studied. The comparison of the hole volume with the specific volume allowed us to estimate the number density of holes to ≈1 nm$\text{}^{-3}$.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 8.

Tytuł:: Environmental Gamma Dose Evaluation During Explosive Materials Analysis by PGNAA Technique Using MCNPX Code
Autorzy:: Nasrabadi, M.
Omidi, S.
Tematy:: 87.52.-g
61.80.-x
78.70.-g; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1401224.pdf Link otwiera się w nowym oknie
Opis:: Increased use of radiation in medicine, industry, and laboratories, requires safe conditions to be provided for its optimal use. One of the cases in which people are exposed to radiation, is during the detection of explosive materials by PGNAA method. Therefore, external dosimetry is necessary for workplaces where the method is used. In this study, Monte Carlo simulation program, MCNPX has been used to simulate gamma dose in the environment during the detection of explosive materials by PGNAA method. The simulated results were validated practically. The results indicate a good agreement between the simulated and measured data. The study demonstrated that MCNPX code can be used effectively for simulating gamma dose in various environments.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 9.

Tytuł:: Electron Beam Induced Modification of Polymer-Like Carbon Coatings
Autorzy:: Plaipaitė-Nalivaiko, R.
Adlienė, D.
Adlys, G.
Tematy:: 78.70.-g
78.66.-w
78.30.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1400455.pdf Link otwiera się w nowym oknie
Opis:: Carbon coatings can possess diamond-like, polymer-like, graphite-like or other properties depending on deposition methods and technological parameters. Structural changes in the polymer-like carbon coatings irradiated by high energy electrons are discussed in the present paper. The polymer-like carbon coatings have been synthesized from $C_2H_2$ gas in the radio frequency dual-plasma reactor using various deposition parameters. Plasma enhancement chemical vapor deposition deposited experimental polymer-like carbon samples were irradiated with high energy electrons in the medical linear accelerator. The investigations of carbon coatings have been carried out using the Fourier-transform infrared, Raman and UV-VIS spectroscopies. Modification of the polymer-like carbon coatings is discussed in relation with radiation induced formation of free radicals and unsaturated bonds along with possible cross-linking processes.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Electrical Resistivity and Positron Lifetime Studies of Precipitation Effects in Al-Cu Alloy
Autorzy:: Αda, P.
Cieslar, M.
Vostrý, P.
Bečvář, F.
Νovotný, I.
Procházka, I.
Tematy:: 61.72.-y
78.70.-g
81.40.-z; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1933483.pdf Link otwiera się w nowym oknie
Opis:: Decomposition of the supersaturated solid solution of 2 at.% Cu in Al was investigated by means of electrical resistivity and high-resolution positron lifetime measurements. The phase composition of this alloy was determined by transmission electron microscopy. Electrical resistivity measurements were performed by a classical four-point method. Positron lifetime spectra were measured by means of a spectrometer consisting of two BaF$\text{}_{2}$ detectors and a standard fast-slow coincidence system. The specimens were first exposed to the solution heat treatment at 783 K for 19 hours with a subsequent quenching. Then the specimens were isochronally annealed in the temperature range 293 ÷ 573 K. Annealing responses of electrical resistivity and positron annihilation were studied. Resistivity measurements as well as transmission electron microscopy observations confirmed the well-known decomposition sequence of the Al-Cu alloy. The decomposition of the alloy was manifested by the decrease in the intensity of positron lifetime component τ$\text{}_{2}$ = (207 ±2 ) ps correlated with simultaneous appearance and increase in the intensity of τ$\text{}_{3}$ = (180 ± 5) ps component. Component τ$\text{}_{2}$ originates from positron annihilation in vacancies trapped at the Guinier-Preston zones while τ$\text{}_{3}$ comes from annihilation of the positrons localized in the misfit dislocations at coherent precipitates of the Al$\text{}_{2}$Cu phase. The shortest observed component τ$\text{}_{1}$ apparently belongs to annihilation of untrapped positrons.
Dostawca treści:: Biblioteka Nauki

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