共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Dobrovolskiy A.E. Yakshin F.D. Tichelaar E. Louis 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(6):560-567
Si/SiC multilayer systems for XUV reflection optics with a periodicity of 10-20 nm were produced by sequential deposition of Si and implantation of 1 keV ions. Only about 3% of the implanted carbon was transferred into the SiC, with a thin, 0.5-1 nm, buried SiC layer being formed. We investigated the effect of thermal annealing on further completion of the carbide layer. For the annealing we used a vacuum furnace, a rapid thermal annealing system in argon atmosphere, and a scanning e-beam, for different temperatures, heating rates, and annealing durations. Annealing to a temperature as low as 600 °C resulted in the formation of a 4.5 nm smooth, amorphous carbide layer in the carbon-implanted region. However, annealing at a higher temperature, 1000 °C, lead to the formation of a rough poly-crystalline carbide layer. The multilayers were characterized by grazing incidence X-ray reflectometry and cross section TEM. 相似文献
2.
J. Wong-Leung M.S. Janson B.G. Svensson A. Hallén D.J.H. Cockayne 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(8):1367-1372
Silicon carbide offers unique applications as a wide bandgap semiconductor. This paper reviews various aspects of ion implantation in 4H-SiC studied with a view to optimise ion implantation in silicon carbide. Al, P and Si ions with keV energies were used. Channelling effects were studied in both a-axis and c-axis crystals as a function of tilts along major orthogonal planes and off the major orthogonal planes. Major axes such as [0 0 0 1] and the and minor axis like the showed long channelling tails and optimum tilts for minimising channelling are recommended. TEM analyses of the samples showed the formation of (0 0 0 1) prismatic loops and the loops as well,in both a and c-cut crystals. We also note the presence of voids only in P implanted samples implanted with amorphising doses. The competing process between damage accumulation and dynamic annealing was studied by determining the critical temperature for the transition between crystalline and amorphous SiC and an activation energy of 1.3 eV is extracted. 相似文献
3.
Single crystal 〈0 0 0 1〉-oriented 6H-SiC was irradiated with Au2+ ions to fluences of 0.032, 0.058 and 0.105 ions/nm2 at 140 K and was subsequently annealed at various temperatures up to 500 K. The relative disorder on both the Si and C sublattices has been determined simultaneously using in situ D+ ion channeling along the 〈0 0 0 1〉 and 〈〉 axes. A higher level of disorder on both the Si and C sublattices is observed along the 〈〉. There is a preferential C disordering and more C interstitials are aligned with 〈0 0 0 1〉. Room-temperature recovery along 〈〉 occurs, which is associated with the 〈0 0 0 1〉-aligned interstitials that annihilate due to close-pair recombination. Disorder recovery between 400 and 500 K is primarily attributed to annihilation of interstitials that are misaligned with 〈0 0 0 1〉 and to epitaxial crystallization. Effects of stacking order in SiC on disorder accumulation are insignificant; however, noticeable differences of low-temperature recovery in Au2+-irradiated 6H-SiC and 4H-SiC are observed. 相似文献
4.
Diffusion properties for volatile fission products iodine and tellurium, and gaseous product xenon in a solid solution of thoria-2 mol% urania doped with fission products for simulating 2 at.% burnup were obtained by studying the release kinetics of the species from trace-irradiated fuel samples at different temperatures using post-irradiation annealing technique. Bulk diffusion coefficients for Xe, I and Te were evaluated in a well-defined powder sample of particle size in the range of 37-45 μm (25 m2 kg−1 BET surface area) with 97% of theoretical density. Temperature dependences of the apparent diffusion coefficients of Xe, I and Te derived from this study could be expressed in the form of Arrhenius equations for the respective cases as ln (s−1) = −(19,480 ± 3300)/T − 9.3 ± 2.2 and ln (s−1) = −(31,234 ± 3000)/T − 3.7 ± 2.0, (1273 ? T/K ? 1773) and ln (s−1) = −(22,755 ± 1364)/T − 0.003 ± 0.775, 1700 ? T/K ? 1800. For Xe diffusion the activation energy and frequency factor are 189 kJ mol−1 and 0.997 s−1, respectively. For I and Te the activation energy values are 162 and 260 kJ mol−1, respectively. The respective frequency factors for I and Te are 9.1 × 10−5 and 2.5 × 10−2 s−1. On comparison with the reported data in pure urania and thoria matrices a lowering of activation energy for all three species was observed in case of the fission product doped matrix. On the other hand the frequency factor has increased only in the case for diffusion of Xe. This suggests different mechanisms of transport for Xe and volatile fission products I and Te in the fuel matrix. 相似文献
5.
R. Sudha 《Journal of Nuclear Materials》2006,348(3):302-310
The diffusivity of manganese in vacuum annealed and cold worked alloy D9 in presence of sodium was measured by the standard tracer technique. The lattice diffusion coefficient of manganese in vacuum annealed alloy D9 specimens in the temperature range 773-873 K is given by the expression and that in cold worked alloy D9 specimens is given by where R is in J K−1 mol−1. The activation energy for diffusion in cold worked specimens is less than that in vacuum annealed specimens. The activation energy for diffusion of manganese in presence of sodium is almost four times less than that in various austenitic stainless steels reported in the literature. 相似文献
6.
7.
J.D. Comins G.O. Amolo S.H. Connell M.J. Witcomb 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(16):2690-2697
Optical methods can provide important insights into the mechanisms and consequences of ion beam interactions with solids. This is illustrated by four distinctly different systems.X- and Y-cut LiNbO3 crystals implanted with 8 MeV Au3+ ions with a fluence of 1 × 1017 ions/cm2 result in gold nanoparticle formation during high temperature annealing. Optical extinction curves simulated by the Mie theory provide the average nanoparticle sizes. TEM studies are in reasonable agreement and confirm a near-spherical nanoparticle shape but with surface facets. Large temperature differences in the nanoparticle creation in the X- and Y-cut crystals are explained by recrystallisation of the initially amorphised regions so as to recreate the prior crystal structure and to result in anisotropic diffusion of the implanted gold.Defect formation in alkali halides using ion beam irradiation has provided new information. Radiation-hard CsI crystals bombarded with 1 MeV protons at 300 K successfully produce F-type centres and V-centres having the structure as identified by optical absorption and Raman studies. The results are discussed in relation to the formation of interstitial iodine aggregates of various types in alkali iodides. Depth profiling of and aggregates created in RbI bombarded with 13.6 MeV/A argon ions at 300 K is discussed.The recrystallisation of an amorphous silicon layer created in crystalline silicon bombarded with 100 keV carbon ions with a fluence of 5 × 1017 ions/cm2 during subsequent high temperature annealing is studied by Raman and Brillouin light scattering.Irradiation of tin-doped indium oxide (ITO) films with 1 MeV protons with fluences from 1 × 1015 to 250 × 1015 ions/cm−2 induces visible darkening over a broad spectral region that shows three stages of development. This is attributed to the formation of defect clusters by a model of defect growth and also high fluence optical absorption studies. X-ray diffraction studies show evidence of a strained lattice after the proton bombardment and recovery after long period storage. The effects are attributed to the annealing of the defects produced. 相似文献
8.
The diffusion of La, a trivalent cation dopant, actinide surrogate, and high-yield fission product, in CeO2, a UO2 nuclear fuel surrogate, during 1.8 MeV Kr+ ion bombardment over a temperature range from 673 K to 1206 K has been measured with secondary ion mass spectroscopy. The diffusivity under these irradiation conditions has been analyzed with a model based on a combination of sink-limited and recombination-limited kinetics. This analysis yielded a cation vacancy migration energy of ∼ 0.4 eV below ∼800 K, were recombination-limited kinetics dominated the behavior. The thermal diffusivity of La in the same system was measured over a range of 873-1073 K and was characterized by an activation enthalpy of . The measurement of both the migration enthalpy and total activation enthalpy separately allows the vacancy formation enthalpy on the cation sublattice to be determined; ∼ 1 eV. The mixing parameter under energetic heavy-ion bombardment at room temperature was measured as well and found to be ∼4 × 10−5 nm5/eV. 相似文献
9.
Crystallographic measurement of the β to α phase transformation and δ-hydride precipitation in a laser-welded Zircaloy-2 ferrule tube were carried out using an electron backscattering diffraction pattern (EBSP). A basket-weave structure with sub-micron lath width caused by quenching from the β to α phase was observed in the heat-affected and fusion zones, and mainly showed a grain boundary misorientation angle of 60° with an <1 1 0> rotation axis. This result is consistent with the Burgers orientation relationship of {1 1 0}β//(0 0 0 1)α and <1 1 1>β//<1 1 0>α for the β to α phase transformation. The texture of the quenched α′ phase was strongly inherited from the original α phase, having a radial (0 0 0 1) basal pole and axial {1 1 0} textures, even in the fusion zone. The primary hydride habit plane in the welded Zircaloy-2 was (0 0 0 1)α//{1 1 1}δ, matching previously obtained results for recrystallized cladding tubes. In addition to the primary habit plane, secondary habit planes were observed for the other low-index planes {1 0 0} and {1 0 1} in the fusion zone. The heterogeneous accumulation of hydrides in the transition zone between heat-affected and unaffected zones was mainly due to the residual stress distribution in the narrow region. 相似文献
10.
K. Hirata Y. Saitoh K. Yamada K. Narumi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):2930-2932
Emission yields of secondary ions necessary for the identification of poly-tyrosine were compared for incident ion impacts of energetic cluster ions (0.8 MeV , 2.4 MeV , and 4.0 MeV ) and swift heavy monoatomic molybdenum ions (4.0 MeV Mo+ and 14 MeV Mo4+) with similar mass to that of the cluster by time-of-flight secondary ion mass analysis combined with secondary ion electric current measurements. The comparison revealed that (1) secondary ion emission yields per impact increase with increasing incident energy within the energy range examined, (2) the 4.0 MeV impact provides higher emission yields than the impact of the monoatomic Mo ion with the same incident energy (4.0 MeV Mo+), and (3) the 2.4 MeV impact exhibits comparable emission yields to that for the Mo ion impact with higher incident energy (14 MeV Mo4+). Energetic cluster ion impacts effectively produce the characteristic secondary ions for poly-tyrosine, which is advantageous for highly sensitive amino acid detection in proteins using time-of-flight secondary ion mass analysis. 相似文献
11.
In order to elucidate the effect of noble metal clusters in spent nuclear fuel on the kinetics of radiation induced spent fuel dissolution we have used Pd particle doped UO2 pellets. The catalytic effect of Pd particles on the kinetics of radiation induced dissolution of UO2 during γ-irradiation in containing solutions purged with N2 and H2 was studied in this work. Four pellets with Pd concentrations of 0%, 0.1%, 1% and 3% were produced to mimic spent nuclear fuel. The pellets were placed in 10 mM aqueous solutions and γ-irradiated, and the dissolution of was measured spectrophotometrically as a function of time. Under N2 atmosphere, 3% Pd prevent the dissolution of uranium by reduction with the radiolytically produced H2, while the other pellets show a rate of dissolution of around 1.6 × 10−9 mol m−2 s−1. Under H2 atmosphere already 0.1% Pd effectively prevents the dissolution of uranium, while the rate of dissolution for the pellet without Pd is 1.4 × 10−9 mol m−2 s−1. It is also shown in experiments without radiation in aqueous solutions containing H2O2 and O2 that ?-particles catalyze the oxidation of the UO2 matrix by these molecular oxidants, and that the kinetics of the catalyzed reactions is close to diffusion controlled. 相似文献
12.
Gui-jiang Li Cong Li Jian Gao 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(9):1964-1970
An attempt that the precipitation hardening steel 17-4PH was conducted by DC plasma nitriding (DCPN) is made to develop a kind of candidate material for nuclear reactor. Nitriding process performed at temperature ? 400 °C takes effect on creation of the layers composed of S-phase (expanded austenite) and (expanded martensite). Up to the temperature of 420 °C, the S-phase peaks disappear due to the transformation occurrence (S-phase → + CrN). For the samples nitrided at temperature ? 450 °C, no evidence of is found owing to a precipitation () taking place. For the 480 °C/4 h treated sample, it is the surface microhardness that plays the lead role in the wear rate reduction but the surface roughness; while for the 400 °C/4 h treated sample, it is both of the surface roughness and the S-phase formation. Dry sliding wear of the untreated 17-4PH is mainly characterized by strong adhesion, abrasion and oxidation mechanism. Samples nitrided at 400 °C which is dominated by slight abrasion and plastic deformation exhibit the best dry sliding wear resistance compared to the samples nitrided at other temperatures. 相似文献
13.
M. Izerrouken T. Benyahia 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(19):2987-2990
Colour centers formation in Al2O3 by reactor neutrons were investigated by optical measurements (absorption and photoluminescence). The irradiation’s were performed at 40 °C, up to fast neutron (En > 1.2 MeV) fluence of 1.4 × 1018 n cm−2. After irradiation the coloration of the sample increases with the neutron fluence and absorption band at about 203, 255, 300, 357 and 450 nm appear in the UV-visible spectrum. The evolution of each absorption bands as a function of fluence and annealing temperature is presented and discussed. The results indicate that at higher fluence and above 350 °C the F+ center starts to aggregate to F center clusters (F2, F2+ and ). These aggregates disappear completely above 650 °C whereas the F and F+ centers persist even after annealing at 900 °C. It is clear also from the results that the absorption band at 300 nm is due to the contribution of both F2 center and interstitial ions. 相似文献
14.
M. Yedji G. Genard G.G. Ross 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(9):2060-2064
The fabrication of reliable isotopic nitrogen standards is achieved in Si through 14N and 15N ion implantation. 60 keV and ions were implanted at 400 °C up to ∼60% peak atomic concentration, yielding nitrogen-saturated silicon layers as measured using resonant nuclear reaction analysis. No isotopic effect has been observed. The nitrogen standards are validated by measurements of stability under ion irradiation. No significant desorption of nitrogen is observed either under a 4He+ ion fluence of 3.36 × 1016 cm−2 or under a 1H+ ion fluence of 8.60 × 1017 cm−2, giving strong evidence that isotopic nitrogen standards can be achieved. 相似文献
15.
Fang Cheng Qiren Zhang Hailin Qiao Xiuwen Zhou 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(15):2403-2407
The experiments indicate that the perfect KMgF3 crystal has no absorption in the visible range, however the electron irradiation induces a complex absorption spectrum. The absorption spectra can be decomposed by five Gaussian bands peaking at 2.5 eV (488 nm), 3.4 eV (359 nm), 4.2 eV (295 nm), 4.6 eV (270 nm) and 5.2 eV (239 nm), respectively. The purpose of this paper is to seek the origins of the absorption bands. The electronic structures and absorption spectra either for the perfect KMgF3 or for KMgF3: with electrical neutrality have been studied by using density functional theory code CASTEP with the lattice structure optimized. The calculation results predicate that KMgF3: also exhibits five absorption bands caused by the existence of the fluorine ion vacancy and the five absorption bands well coincide with the experimental results. It is believable that the five absorption bands are related to in KMgF3 crystal produced by the electron irradiation. 相似文献
16.
Haiyan Zhang Tingyu Liu Qiren Zhang Xi’en Wang Xiaofeng Guo Min Song Jigang Yin 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(7):1056-1060
The electronic structures, dielectric function and absorption spectra for the perfect BaWO4 (BWO) crystal and the BWO crystal containing barium vacancy () have been studied using density functional theory code CASTEP with the lattice structure optimized. The results indicate that the optical properties of the BWO crystal exhibit anisotropy and its optical symmetry coincide with lattice structure geometry of the BWO crystal. For the BWO crystal containing , there exhibit four absorption bands peaking at 0.71 eV (1751 nm), 1.85 eV (672 nm), 3.43 eV (362 nm) and 3.85 eV (322 nm), respectively. The origins of the 370 nm absorption band should be related to the . 相似文献
17.
Y. Wang M. Qi D.X. Li 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(6):881-885
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. 相似文献
18.
Satoshi Ninomiya Kazuya Ichiki Takaaki Aoki Jiro Matsuo 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(16):2601-2604
We investigated the effects of size and energy of large incident Ar cluster ions on the secondary ion emission of Si. The secondary ions were measured using a double deflection method and a time-of-flight (TOF) technique. The size of the incident Ar cluster ions was between a few hundreds and several tens of thousands of atoms, and the energy up to 60 keV. Under the incidence of keV energy atomic Ar ions, mainly atomic Si ions were detected, whereas Si cluster ions were rarely observed. On the other hand, under the incidence of large Ar cluster ions, the dominant secondary ions were (2 ? n ? 11). It has become clear that the yield ratio of secondary Si cluster ions was determined by the velocity of the incident cluster ions, and this strong dependence of the yield ratio on incident velocity should be related to the mechanisms of secondary ion emission under large Ar cluster ion bombardment. 相似文献
19.
C. Wrede K. Deryckx B.M. Freeman A. García G.C. Harper A.S.C. Palmer D.A. Short D.I. Will 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(23):3482-2729
The preparation of isotopically pure targets of 20Ne, 24Mg, 28Si, 32S, and 36Ar by the implantation of 25-70 keV ions into carbon foils is described. 相似文献
20.
Ivo Zizak Nora Darowski Gerhard Schumacher Walter Assmann 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(6):944-948
Significant changes in texture occur in nanocrystalline Ti, TiN and NiO layers during irradiation with 350 MeV Au ions. The angle between ion beam and layer normal Θ was between 30° and 70°. The major effect is a collective rotation of the nanocrystals. In case of ω layers the texture rotated by more than 70° at an ion fluence . In addition to grain rotation, the layers exhibit a shear motion like that observed previously with amorphous materials. Below about the grain growth is small and grain rotation is reversible, i.e. reversing the sign of Θ and applying the same Φt, the grains roll back into their original orientation. The second observed effect is the alignment of the grains, whose coalescence eventually leads to a mosaic crystal. However, grain rotation is absent or immeasurably small in micro-crystalline titanium. An attempt to understand the processes in nanocrystalline materials in terms of amorphous grain boundaries, as well as the disclination dipole diffusion along the grain boundary was made. 相似文献