Effects of Mg-ion implantation in α-Al2O3 and α-Al2O3:Mg crystals: Electrical conductivity and electronic structure changes

Undoped and Mg-doped α-Al₂O₃ single crystals were implanted with Mg ions, with an energy of 90 keV and a fluence of 10¹⁷ ions/cm². DC electrical measurements using the four-point probe method, between 295 and 428 K, were used to characterize the electrical conductivity of the implanted area. Measurements in this temperature range indicate that the electrical conductivity after implantation is thermally activated with an activation energy of about 0.03 eV both in undoped and in reduced Mg-doped α-Al₂O₃ crystals, whereas the activation energy in oxidized Mg-doped α-Al₂O₃ crystals remains close to that before implantation. The I-V characteristics of the latter samples reveal a blocking behavior of the electrical contacts on the implanted area in contrast to the ohmic contacts observed in α-Al₂O₃ single crystals with the c-axis perpendicular to the broad face, where the Mg ions were implanted. We conclude that the enhancement in conductivity observed in the implanted regions is related to the intrinsic defects created by the implantation, rather than to the implanted Mg ions. The relationship between the oxygen vacancy concentrations at different stages of etching and the changes in the electronic structure, the chemical bonding, and the Al³⁺(2p)/O²⁻(1s) and Mg²⁺(1s)/O²⁻(1s) relative intensities was studied by X-ray Photoemission Spectroscopy.     

Morphology and interface structure of α-Fe2O3 islands grown on sapphire by ion-implantation and annealing

The morphology and interface structure of α-Fe₂O₃ islands grown on α-Al₂O₃ single crystals (sapphire) by Fe-ion-implantation and annealing in an oxidizing atmosphere have been studied using transmission electron microscopy. The α-Fe₂O₃ islands have the orientation relationship of and with sapphire. The typical outline of α-Fe₂O₃ islands consists of two (0 0 0 1) and six planes. The interfaces between α-Fe₂O₃ islands and sapphire are semicoherent, that is coherent regions separated by misfit dislocations at the interfaces. When imaged along the direction, the projected Burgers vector is determined to be . When imaged along the direction, the projected Burgers vector is determined to be . These misfit dislocations form a network structure at the interface to accommodate the mismatch between the lattices of the α-Fe₂O₃ and the α-Al₂O₃.     

Photon yield for ultraviolet and visible emission from CF4 excited with α-particles

Carbon tetrafluoride (CF₄) photon yield, defined as the number of photons emitted per 1 MeV of energy deposited in the gas is reported for the ultraviolet (220-500 nm) and visible (500-800 nm) emission in the pressure range from 0.5 to 5 bar. An Am-241 α-source was used for gas excitation. Emission spectra (corrected for the response of the detection system) are given in the range from 200 to 800 nm. The visible emission, which is weak at 0.5 bar, strongly increases with gas pressure and dominates the emission spectrum at 5 bar.     

K-shell ionization cross sections of Cl and Lα, Lβ X-ray production cross sections of Ba by 6-30 keV electron impact

The absolute K-shell ionization cross sections of Cl and L_α, L_β X-ray production cross sections of Ba by 6-30 keV electron impact have been measured. The target was prepared by evaporating the thin film of compound BaCl₂ to the thick pure carbon substrate. The effects of multiple scattering of electrons penetrating the target films, electrons reflected from the thick pure carbon substrates and Bremsstrahlung photons produced when incident electrons impacted on the targets are corrected by using Monte Carlo method. For Ba L-shell X-ray characteristic peaks, the spectra were fitted by using spectrum-fitting program ALLFIT to extract more accurately the L_α and L_β peak counts. The experimental results, reported here for the first time in the energy region of 6-30 keV, were compared with some theoretical results developed recently.     

Effects of γ-ray irradiation on the C-V and G/ω-V characteristics of Al/SiO2/p-Si (MIS) structures

The effect of the ⁶⁰C_o (γ-ray) exposure on the electrical characteristics of Al/SiO₂/p-Si (MIS) structures has been investigated using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. The MIS structures were stressed with a bias of 0 V during ⁶⁰C_oγ-sources irradiation with the total dose range from 0 to 25 kGy. The C-V and G/ω-V characteristics were measured at 500 kHz and room temperature before and after ⁶⁰C_oγ-ray irradiation. The results indicated that γ-irradiation caused an increase in the barrier height Φ_B, interface states N_ss and depletion layer width W_D obtained from reverse bias C-V measurements. The series resistance R_s profile for various radiation doses was obtained from forward and reverse bias C-V and G/ω-V measurements. Both C-V and G/ω-V characteristics indicate that the total dose radiation hardness of MIS structures may be limited by the decisive properties of the SiO₂/Si interface to radiation-induced damage. After γ-irradiation, the decrease in capacitance of MIS structure results in the increase in the semiconductor depletion width.     

Investigation of the level spectra of nuclei in the northeast region of doubly magic 40Ca with intruder orbit g9∕2

This study utilizes large-scale shell model calculations with the extended pairing and multipole–multipole force model(EPQQM) to investigate low-lying states in the nuclei of ⁴²Ca,⁴²Sc,and ^42-44Ti.The model space in this study includes the fp shell as well as the intruder g_9∕2 orbit,which accurately reproduces the positive parity levels observed in the aforementioned nuclei and predicts high energy states with negative parity coupled with the intruder ...     

Effect of Gd on neutron absorption properties and electrochemical corrosion behavior of Zr–Gd alloy in boiling concentrated HNO3

A Zr–Gd alloy with neutron poisoning properties and resistance to boiling concentrated HNO3 corrosion was developed based on a corrosion-resistant Zr-702 alloy to meet the demand for neutron shielding in the closed-loop treatment of spent fuel and the nuclear chemical industry. In this study, 1 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 9 wt.% Zr–Gd alloys were designed and fabricated with Zr-702 as the control element. The electrochemical behavior of the Zr–Gd alloys in boiling concentrated HNO3 was inv...     

In situ X-ray diffraction study of the δ to α′ isothermal martensitic transformation kinetics in a Pu-Ga alloy

The sequence of phase formation and the isothermal kinetics of the δ to α′ phase transformation in a Pu-1.9 at.% Ga alloy are investigated with in situ X-ray diffraction at the Advanced Photon Source. It has been proposed that the formation of a γ′ intermediate phase may be responsible for the unusual double-C curve kinetics reported for this isothermal martensitic transformation. While a γ′ intermediate phase was not observed at either −120 °C or −155 °C, an unexplained shoulder on the δ (1 1 1) peak was detected at −155 °C. The isothermal kinetics of the δ → α′ transformation appear to fit a Johnson-Mehl-Avrami-Kolmogorov equation, but the exponent is not described by existing JMAK theory. The double-C curve kinetics of the δ to α′ transformation remain unresolved in plutonium science, and understanding this behavior is key to predicting phase stability in aging Pu-Ga alloys.     

Nucleation and growth of self-interstitial atom clusters in β-SiC during irradiation: Kinetic Monte-Carlo modeling

In order to clarify formation kinetics of self-interstitial atoms (SIA) clusters in cubic silicon carbide (β-SiC) during irradiation, the nucleation and growth process of SIA-clusters have been investigated by a kinetic Monte-Carlo (KMC) simulation technique. It has been found from the KMC simulations that the formation kinetics of SIA-clusters in β-SiC during irradiation is classified into the following two types, depending on temperature. At relatively high temperatures, the thermal stability of an SIA-cluster is crucial for the nucleation and growth of the cluster, in which the composition of the cluster is almost stoichiometric. In contrast, at relatively low temperatures where the cluster thermal stability is no longer crucial, even an SIA-cluster far from stoichiometric composition is formed.     

Comparison of hydrogen isotope retention and irradiation damage behaviors in tungsten and SS-316 with simultaneous C+–D2+ implantation

Behaviors of hydrogen isotope retention and damages in tungsten and SS-316 with simultaneous C⁺–D₂⁺ implantation were compared to those with only D₂⁺ implantation using X-ray photoelectron spectroscopy (XPS), Thermal desorption spectroscopy (TDS), glow discharge-optical emission spectroscopy (GD-OES) and Transmission electron microscopy (TEM).The total D retention for SS-316 with only D₂⁺ implantation was about 45% as large as that for tungsten. The D retention for simultaneous C⁺–D₂⁺ implanted tungsten and SS-316 clearly increased as a factor of 1.7, which is almost the same among these samples. The density of dislocation loops was enhanced by the simultaneous C⁺–D₂⁺ implantation, indicating the D trapping site would be produced by C⁺ implantation. As for the D desorption temperature, small shift toward lower temperature side was found for SS-316 compared to tungsten, indicating the D trapping energy by dislocation loops and grain boundary for SS-316 is lower than that for tungsten.     

Synchrotron radiation X-ray fluorescence analysis of Fe,Zn and Cu in mice brain associated with Parkinson’s disease

The contents and distributions of metal elements in the brain are closely related to neurodegenerative diseases.In this study, we examined Fe, Cu and Zn contents in the brain section associated with Parkinson‘s disease(PD)using synchrotron radiation X-ray fluorescence(SRXRF). PD mouse model induced by 1-methyl-4-phenyl-1,2,3,6-terahydropyridine(MPTP) was used for the elemental analysis(e.g., Fe, Cu and Zn) in the substantia nigra pars compacta(SNpc) region of mice brain tissue samples. We found that mice in the MPTP group had higher contents of Fe, Cu and Zn in the SNpc than the control group. After treating the PD mice with rapamycin, the contents of Fe, Cu and Zn were reduced, the dopamine neurons and motor function were rescued correspondingly. The results prompted that the SRXRF provided an ideal method for tracing and analyzing the metal elements in the brain section to assess the pathological changes of PD model and the therapeutic effect of drugs.     

Study on the corrosion behavior of 316H stainless steel in molten NaCl–KCl–MgCl2 salts with and without purification

The corrosion behavior of 316H stainless steel (SS) in the impure and purified Na Cl–KCl–Mg Cl₂ salt was investigated at700°C.Results indicate that the main deleterious impurity induced corrosion in the impure salt was the absorbed moisture,present in the form of Mg Cl₂·6H₂O.316H SS occurred severe intergranular corrosion with a corrosion depth of 130μm for1000 h in the impure Na Cl–KCl–Mg Cl₂ salt.In contrast,the purification treatment of molten chlor...     

Molecular dynamics evaluation of the impact of Ga, He, and vacancy concentration on the mechanical properties of Ga-stabilized δ-Pu

The effects of self-irradiation on the mechanical properties of Ga-stabilized δ-Pu are investigated by means of classical molecular dynamics simulations using a modified embedded-atom method interatomic potential. The impact that variations in the concentration of Ga, He, and vacancies have on the elastic properties (Young’s modulus, Poisson’s ratio, shear modulus, and bulk modulus) of Ga-stabilized δ-Pu is determined through CMD simulation. The effect that variations in these concentrations have on plastic flow is assessed at strain rates of 10⁷-10¹⁰ s⁻¹. Comparison is made to experimental data.     

Electroluminescence from metal-oxide-silicon tunneling diode with ion-beam-synthesized β-FeSi2 precipitates embedded in the active region

A metal-oxide-silicon (MOS) tunneling light-emitting diode is fabricated with ion-beam-synthesized β-FeSi₂ precipitates embedded in the active region. Fe ions were implanted into p⁻-100 silicon substrate at cryogenic temperature (∼−120 °C), followed by rapid thermal oxidation (RTO). Under constant voltage biased in accumulation and at temperatures down to 80 K, electroluminescence (EL) with wavelength peaking at ∼1.5 μm is observed at a current density of about 2.0 A/cm². Light output increases linearly with current density. Temperature dependence of the EL shows that the luminescence is due to interband recombination in the crystalline precipitates. The strain in these isolated precipitates may contribute to the luminescence properties of β-FeSi₂ in silicon.     

The Influence of Triaxiality Parameter γ on the Chiral Doublet Bands with (πg9/2)～（-1）(νh11/2)～2 Configuration

The chiral doublet bands with three-quasiparticle configuration (πg 9/2) 1 (νh 11/2) 2 are studied by the fully quantal triaxial particle rotor model.The energy spectra and B(M1)/B(E2) ratios of the doublet bands with different triaxiality parameter γ are systemati-cally analyzed.It is found that γ is a sensitive parameter for the properties of these doublet bands.     

L1 and L2 sub-shell fluorescence yields for elements with 64 ? Z ? 70

The L₁ and L₂ sub-shell fluorescence yields have been deduced for elements with 64 ? Z ? 70 from the L_k(k = l, α, β_1,4, β_3,6, β_2,15,9,10,7, γ_1,5 and γ_2,3,4) X-ray production cross sections measured at 22.6 keV incident photon energy using a spectrometer involving a disc type radioisotope of Cd¹⁰⁹ as a photon source and a Peltier cooled X-ray detector. The incident photon intensity, detector efficiency and geometrical factor have been determined from the K X-ray yields emitted from elemental targets with 20 ? Z ? 42 in the same geometrical setup and from knowledge of the K shell cross sections. The present deduced ω₁(exp) values, for elements with 64 ? Z ? 70, are found to be in good agreement with those tabulated by Campbell (J.L. Campbell, Atom. Data Nucl. Data Tables 95 (2009) 115), where as these are, on an average, higher by 19% and 24% than those based on the Dirac-Hartree-Slater model (S. Puri et al., X-ray Spectrometry 22 (1993) 358) and the semi-empirical values compiled by Krause (M.O. Krause, J. Phys. Chem. Ref. Data 8 (1979) 307), respectively. The present deduced ω₂(exp) values are found to be in good agreement with those based on the Dirac-Hartree-Slater model and are higher by up to ∼13% than the semi-empirical values for the elements under investigation.     

Rossi-α and Feynmann Y functions for non-Poissonian pulsed sources of neutrons in the stochastic pulsing method: Application to subcriticality monitoring in ADS and comparison with the results of Poissonian pulsed neutron sources

In this paper, analytical expressions for the Rossi-α and the Feynmann Y functions are deduced for the case of Poissonian and non-Poissonian neutron sources when the stochastic pulsing method is used. These analytical expressions are used to fit the experimental data and to obtain the prompt neutron time constant. Also we perform in this paper a comparison of the results obtained for the Rossi-α and Feynmann Y functions with Poissonian and non-Poissonian neutron sources, and we study how much change the shape of these functions when the fission probability decreases and the capture probability increases due to the depletion with time of the fuel, and the increase of the fission products. Some comparisons with experimental data and with the results of other authors have been performed. Another important question analyzed in this paper and that it is interesting from an academic point of view is that the average number of detected counts induced by one single neutron injected in the system at an arbitrary time t′, should obey in point kinetics theory an adjoint equation in the time domain. Also the cross-factorial moment of the number of counts induced by one neutron in two counting intervals should obey also an adjoint equation in the time domain with a source term that depends on the first moments. These results are a consequence of more general results that have been obtained using stochastic transport theory for the one particle probability generating function or Kernel generating function.     

Yield of H2O2in Gas-Liquid Phase with Pulsed DBD简

Electric discharge in water can generate a large number of oxidants such as ozone, hydrogen peroxide and hydroxyl radicals. In this paper, a non-thermal plasma processing system was established by means of pulsed dielectric barrier discharge in gas-liquid phase. The electrodes of discharge reactor were staggered. The yield of H2O2 was enhanced after discharge. The effects of discharge time, discharge voltage, frequency, initial pH value, and feed gas were investigated. The concentration of hydrogen peroxide and ozone was measured after discharge. The experimental results were fully analyzed. The chemical reaction equations in water were given as much as possible. At last, the water containing Rhodamine B was tested in this system. The degradation rate came to 94.22% in 30 min.     

Proton and neutron alignments of the k^ π=5/2^- band in ^79Kr

An experimental study of high-spin states in ^79Kr has been performed at the GASP array using the reaction ^55Mn(^20Si, αpn),Nine new states along with 10 new gamma ray transitions were found in the k^ π=5/2^- band in ^79Kr Three band crossings,associated with the allignments of a πg9/2 pair and a πg9/2 pair and also a high-j 5h11/2 intrude orbital,were observed at rotational frequency h=0.50,0.65 and 0.90 MeV,respectively ,A cranked shell model analysis has been made to interpret the experimental results.     

Experimental stopping powers of Al,Mg, F and O ions in ZrO2 in the 0.1–0.6 MeV/u energy range

The study of the stopping and range of heavy ions (Z > 3) in matter isdsc cfddc of both fundamental and practical interest as heavy ions find increasing usage in a wide range of ion beam based techniques. While semi-empirical formulations like the widely used SRIM code can predict the stopping powers of hydrogen and helium in many elemental and compound targets over a wide range of energies quite well, their predictive accuracy for heavy ions is not as good. This is mainly due to the lack of heavy ion experimental stopping power data on which such codes are based. We present results of measurements performed using a Time of Flight–Energy spectrometer to determine the stopping powers of O, F, Mg and Al ions in the oxide ceramic ZrO₂ within the 0.1–0.6 MeV/u energy range. Possible SRIM correction (or correlation) factors for F, Mg and Al ions were extracted from quantitative comparisons of experimental and predicted stopping power values.