Uranium-molybdenum nuclear fuel plates behaviour under heavy ion irradiation: An X-ray diffraction analysis

Heavy ion irradiation has been proposed for discriminating UMo/Al specimens which are good candidates for research reactor fuels. Two UMo/Al dispersed fuels (U-7 wt%Mo/Al and U-10 wt%Mo/Al) have been irradiated with a 80 MeV ¹²⁷I beam up to an ion fluence of 2 × 10¹⁷ cm⁻². Microscopy and mainly X-ray diffraction using large and micrometer sized beams have enabled to characterize the grown interaction layer: UAl₃ appears to be the only produced crystallized phase. The presence of an amorphous additional phase can however not be excluded. These results are in good agreement with characterizations performed on in-pile irradiated fuels and encourage new studies with heavy ion irradiation.     

Recharging processes, radiation induced strain and changes of OH bands under H ion implantation in Ti doped lithium niobate

A systematic analysis of variations in structural and optical characteristics of Z-cut plates of titanium doped congruent lithium niobate single crystals implanted with 120 keV proton beam at various fluences of 10¹⁵, 10¹⁶ and 10¹⁷ protons/cm² is presented. Through, high resolution X-ray diffraction, atomic force microscopy, Fourier transform infrared and UV-visible-NIR analysis of congruent lithium niobate, the correlation of properties before and after implantation are discussed. HRXRD (0 0 6) reflection by Triple Crystal Mode shows that both tensile and compressive strain peak are produced by the high fluence implantation. A distinct tensile peak was observed from implanted region for a fluence of 10¹⁶ protons/cm². AFM micrographs indicate mountain ridges, bumps and protrusions on target surface on implantation. UV-visible-NIR spectra reveal an increase in charge transfer between Ti³⁺/Ti⁴⁺ and ligand oxygen for implantation with 10¹⁵ protons/cm², while spectra for higher fluence implanted samples show complex absorption band in the region from 380-1100 nm. Variations of OH⁻ stretching vibration mode were observed for cLN Pure, cLNT2% virgin, and implanted samples with FTIR spectra. The concentration of OH⁻ ion before and after implantation was calculated from integral absorption intensity. The effect of 120 keV proton implantation induced structural, surface and optical studies were correlated.     

Effect of swift heavy ion irradiation in W/Co multilayer structures

Present study reports effect of swift heavy ion irradiation on structural and magnetic properties of sputtered W/Co multilayer structures (MLS) having bilayer compositions of [W(10 Å)/Co(20 Å)]_5BL and [W(20 Å)/Co(20 Å)]_5BL. These MLS are irradiated by 120 MeV Au⁹⁺ ions up to fluence of 1 × 10¹³ ions/cm². X-ray reflectivity (XRR), wide-angle X-ray diffraction (WAXD), cross-sectional transmission electron microscopy (X-TEM) and magneto optical Kerr effect (MOKE) techniques are used for structural and magnetic characterization of pristine and irradiated MLS. Analysis of XRR data using Parratt’s formalism shows a significant increase in W/Co interface roughness. WAXD and X-TEM studies reveals that intra-layer microstructure of Co-layers in MLS becomes nano-crystalline on irradiation. MOKE study shows slight increase in coercivity at higher fluence, which may be due to increase in surface and interface roughness after recrystallization of Co-layers.     

Ion-beam irradiation effects on reactively sputtered CrN thin films

The present study deals with CrN/Si bilayers irradiated at room temperature (RT) with 120 keV Ar ions. The CrN layers were deposited by d.c. reactive sputtering on Si(1 0 0) wafers, at different nitrogen partial pressures (2 × 10⁻⁴, 3.5 × 10⁻⁴ and 5 × 10⁻⁴ mbar), to a total thickness of 240-280 nm. The substrates were held at room temperature (RT) or 150 °C during deposition. After deposition the CrN/Si bilayers were irradiated up to fluences of 1 × 10¹⁵ and 1 × 10¹⁶ ions/cm². Structural characterization was performed with Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and grazing angle X-ray diffraction (XRD). For the highest nitrogen pressure (5 × 10⁻⁴ mbar) a pure stoichiometric CrN phase was achieved. The results showed that Ar ion irradiation resulted in the variation of the lattice constants, micro-strain and mean grain size of the CrN layers. The observed microstructural changes are due to the formation of the high density damage region in the CrN thin film structure.     

10 MeV Au ion irradiation effects in an MgO-HfO2 ceramic-ceramic (CERCER) composite

Room temperature ion irradiation damage studies were performed on a ceramic composite intended to emulate a dispersion nuclear fuel. The composite is composed of 90-mole% MgO and 10-mole% HfO₂. The as-synthesized composite was found to consist of Mg₂Hf₅O₁₂ (and some residual HfO₂) particles embedded in an MgO matrix. X-ray diffraction revealed that nearly all of the initial HfO₂ reacted with some MgO to form Mg₂Hf₅O₁₂. Ion irradiations were performed using 10 MeV Au³⁺ ions at room temperature over a fluence range of 5 × 10¹⁶-5 × 10²⁰ Au/m². Irradiated samples were characterized using both grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM), the latter using both selected-area electron diffraction (SAED) and micro-diffraction (μD) on samples prepared in cross-sectional geometry. Both GIXRD and TEM electron diffraction measurements on a specimen irradiated to a fluence of 5 × 10²⁰ Au/cm², revealed that the initial rhombohedral Mg₂Hf₅O₁₂ phase was transformed into a cubic-Mg₂Hf₅O₁₂ phase. Finally, it is important to note that at the highest ion fluence used in this investigation (5 × 10²⁰ Au/m²), both the MgO matrix and the Mg₂Hf₅O₁₂ second phase remained crystalline.     

Optical and structural properties of ZnO thin films; effects of high energy electron irradiation and annealing

High energy electron irradiation (HEEI) effects on the as-grown and annealed ZnO thin films grown by electrochemical deposition were investigated. Both samples were exposed to the sequential electron irradiations of 6, 12 and 15 MeV energies at a fluence of 1 × 10¹² e⁻/cm². The results of X-ray diffraction suggest that a highly strong crystallographic structure can be produced by annealing process. Photoluminescence (PL) studies show that the EI produces violet emission which results from the zinc interstitial. Recombination lifetime (RL) values of the both films reveal that the high quality crystals are obtained. The decreasing trends of RL values with increasing electron energy have been explained by the formation of crystal defects due to the HEEI.     

Oxygen ion irradiation effect on corrosion behavior of titanium in nitric acid medium

The corrosion assessment and surface layer properties after O⁵⁺ ion irradiation of commercially pure titanium (CP-Ti) has been studied in 11.5 N HNO₃. CP-Ti specimen was irradiated at different fluences of 1 × 10¹³, 1 × 10¹⁴ and 1 × 10¹⁵ ions/cm² below 313 K, using 116 MeV O⁵⁺ ions source. The corrosion resistance and surface layer were evaluated by using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and glancing-angle X-ray diffraction (GXRD) methods. The potentiodynamic anodic polarization results of CP-Ti revealed that increased in ion fluence (1 × 10¹³-1 × 10¹⁵ ions/cm²) resulted in increased passive current density due to higher anodic dissolution. SEM micrographs and GXRD analysis corroborated these results showing irradiation damage after corrosion test and modified oxide layer by O⁵⁺ ion irradiation was observed. The EIS studies revealed that the stability and passive film resistance varied depending on the fluence of ion irradiation. The GXRD patterns of O⁵⁺ ion irradiated CP-Ti revealed the oxides formed are mostly TiO₂, Ti₂O₃ and TiO. In this paper, the effects of O⁵⁺ ion irradiation on material integrity and corrosion behavior of CP-Ti in nitric acid are described.     

Effect of swift heavy ion irradiation on hydrothermally synthesized hydroxyapatite ceramics

The effect of swift heavy ion irradiation on hydroxyapatite (HAp) ceramic - a bone mineral was investigated. The irradiation experiment was conducted using oxygen ions at energy of 100 MeV with three different fluences of 10¹², 10¹³, 10¹⁴ ions/cm². The irradiated samples were characterized by glancing angle X-ray diffraction (GXRD), atomic force microscopy (AFM), dynamic light scattering (DLS), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). GXRD confirmed incomplete amorphisation of HAp with increase in fluence. There was considerable reduction in particle size on irradiation leading to nanosized HAp (upto 53 nm). PL studies showed emission in the visible wavelength region. The irradiated samples exhibited better bioactivity than the pristine HAp.     

Swift heavy ion induced structural modifications in zircon and scheelite phases of ThGeO4

Structural modifications in the zircon and scheelite phases of ThGeO₄ induced by swift heavy ions (93 MeV Ni⁷⁺) at different fluences as well as pressure quenching effects are reported. X-ray diffraction and Raman measurements at room temperature on the irradiated zircon phase of ThGeO₄ indicate the occurrence of stresses that lead to a reduction of the cell volume up to 2% followed by its transformation to a mixture of nano-crystalline and amorphous scheelite phases. Irradiation of the zircon phase at liquid nitrogen temperature induces amorphization at a lower fluence (7.5 × 10¹⁶ ions/m²), as compared to that at room temperature (6 × 10¹⁷ ions/m²). Scheelite type ThGeO₄ irradiated at room temperature undergoes complete amorphization at a lower fluence of 7.5 × 10¹⁶ ions/m² without any volume reduction. The track radii deduced from X-ray diffraction measurements on room temperature irradiated zircon, scheelite and low temperature irradiated zircon phases of ThGeO₄ are, 3.9, 3.5 and 4.5 nm, respectively. X-ray structural investigations on the zircon phase of ThGeO₄ recovered after pressurization to about 3.5 and 9 GPa at ambient temperature show the coexistence of zircon and disordered scheelite phases with a larger fraction of scheelite phase occurring at 9 GPa. On the other hand, the scheelite phase quenched from 9 GPa shows crystalline scheelite phase pattern.     

Radiation damage effects in candidate titanates for Pu disposition: Zirconolite

Results from studies of radiation-induced damage from the alpha decay of ²³⁸Pu on the density and crystal structure of a nominally phase-pure zirconolite and two other zirconolite-bearing ceramics are discussed. Macro and micro swelling were found to be temperature independent, whereas the density determined with He gas pycnometry was temperature dependent. Approximately 2.6 × 10¹⁸ α/g were needed to render the specimens X-ray amorphous- more to saturate the swelling. Unlike pyrochlore-based ceramics, we did not observe any phase changes associated with storage temperature and damage ingrowth. The forward dissolution rate at a pH value of 2 for material containing essentially all zirconolite is 1.7(4) × 10⁻³ g/(m² d) with very little pH dependence and no dependence on the amount of radiation-induced damage. Even after the radiation-induced swelling saturated, the specimens remained physically intact with no evidence for microcracking. Thus, the material remains physically a viable material for the disposition of surplus weapons-grade Pu.     

Synchrotron X-ray induced damage in polymer (PS) thin films

Thin polystyrene (PS) films (M_w = 234,000) are spin coated on silicon substrates with a Chromium (Cr) layer as a sandwiched metallic layer that produces photoelectrons (by synchrotron X-rays). Earlier studies on synchrotron radiation damage in PS films, without metallic layer, have shown a decrease in interfacial roughness and a slight increase in thickness, at temperatures below T_g [A.G. Richter, R. Guico, K. Shull, J. Wang, Macromolecules 39 (2006) 1545]. Similar trend is observed in the presence of a thin layer of Cr film (∼2.5 nm). For the sample with a thick Cr layer the opposite effect was observed for X-ray radiation damage. For the 50 nm thick Cr film system thickness of the polystyrene film decreased by ≈4.4% which amount to a loss of about 0.021 nm³ per incident photon in the fluence range studied (6.8 × 10⁹ photons mm⁻² to 1 × 10¹⁴ photons mm⁻²). Interfacial roughness also increased from about 1.0 nm to 2.1 nm in the process. These effects are explained by invoking the presence of more number of X-ray induced photoelectrons and secondary electrons for 50 nm thick Cr film case compared to 2.5 nm thin film case.     

Effects of O swift heavy ion irradiation on indium oxide thin films

Indium oxide thin films deposited by spray pyrolysis were irradiated by 100 MeV O⁷⁺ ions with different fluences of 5 × 10¹¹, 1 × 10¹² and 1 × 10¹³ ions/cm². X-ray diffraction analysis confirmed the structure of indium oxide with cubic bixbyite. The strongest (2 2 2) orientation observed from the as-deposited films was shifted to (4 0 0) after irradiation. Furthermore, the intensity of the (4 0 0) orientation was decreased with increasing fluence together with an increase in (2 2 2) intensity. Films irradiated with maximum fluence exhibited an amorphous component. The mobility of the as-deposited indium oxide films was decreased from ∼78.9 to 43.0 cm²/V s, following irradiation. Films irradiated with a fluence of 5 × 10¹¹ ions/cm² showed a better combination of electrical properties, with a resistivity of 4.57 × 10⁻³ Ω cm, carrier concentration of 2.2 × 10¹⁹ cm⁻³ and mobility of 61.0 cm²/V s. The average transmittance obtained from the as-deposited films decreased from ∼81% to 72%, when irradiated with a fluence of 5 × 10¹¹ ions/cm². The surface microstructures confirmed that the irregularly shaped grains seen on the surface of the as-deposited films is modified as “radish-like” morphology when irradiated with a fluence of 5 × 10¹¹ ions/cm².     

Tailoring optical and electrical properties of MgO thin films by 1.5 MeV H implantation to fluences

Thin films of magnesia (MgO) with (1 0 0) dominant orientations were implanted with 1.5 MeV H⁺ ions at room temperature to various fluences of 10¹³, 10¹⁴ and 10¹⁵ ions/cm². X-ray analysis unambiguously showed crystallinity even after a peak damage fluence of 10¹⁵ ions/cm². Rutherford backscattering spectrometry combined with ion channeling (RBS/C) was used to analyze radiation damages and defect distributions. Optical absorption band observed at 5.7 eV in implanted films was assigned to the anion vacancies and the defect was completely disappeared on annealing at 450 °C. Number of F-type defects estimated was 9.42 × 10¹⁵ cm⁻² for the film implanted with 10¹⁵ ions/cm². DC electrical conductivity of 4.02 × 10⁻⁴ S cm⁻¹ was observed in the implanted region which was three orders higher than the as-deposited films. In unison, film surface was modified as a result of the formation of aggregates caused by the atomic mixing of native matrix atoms (Mg and O) and precipitated hydrogen.     

Surface morphology and deuterium retention in tungsten oxide layers exposed to low-energy, high flux D plasma

Surface morphology and deuterium retention in tungsten oxide layers (WO_3−z, z ? 0.25) grown on polycrystalline and recrystallized W substrates have been examined after exposure to a low-energy (38 eV/D), high flux (10²² D/m² s) D plasma to an ion fluence of 10²⁶ D/m² at various temperatures (up to ∼700 K). Characterization methods used were scanning electron microscopy, X-ray diffraction, Rutherford backscattering spectroscopy, and the D(³He,p)⁴He nuclear reaction analysis. During exposure to the D plasma at temperatures of 340-615 K, a partial reduction of the tungsten oxide takes place in the near-surface layer up to 0.3 μm in depth. Even at around room temperature, deuterium atoms diffuse several micrometers into the tungsten oxide. The high D concentration of about 0.1 D/W observed in the first micrometers below the surface at temperatures below 500 K can be related mainly to D atoms chemically bonded to O atoms. As the exposure temperature increases, the D concentration decreases, reaching about 2 × 10⁻⁴ D/W at 615 K. At plasma exposure temperatures of about 700 K, the oxide layer shrinks and loses a large fraction of oxygen.     

Flux dependent MeV ion induced modification of nano-Ag/Si system

Thin films of Ag (1.5 nm thick) are grown on Si (1 1 1) substrates using evaporation method in high vacuum condition and due to non-wetting nature of silver, isolated islands of mean size ≈12.0 nm have been formed on the surface. Au²⁺ (1.5 MeV) ions have been used to irradiate the above systems at various fluences (5 × 10¹³-1 × 10¹⁵ cm⁻²) at an impact angle of 5° and at a flux of 6.3 × 10¹² cm⁻² s⁻¹ (corresponding to a beam current density of 2.0 μA cm⁻² for Au²⁺ ions). Ion beam induced embedding is observed to begin at a fluence of 1 × 10¹⁴ cm⁻² for this high flux whereas low flux irradiations (current density ≈ 0.02 μA cm⁻²) of Au²⁺ ions under similar irradiation conditions did not yield embedding (impact angle 5°). High resolution transmission electron microscopy measurement showed no mixing in the form of silicide formation. These results are compared with high flux modifications in Au/Si system.     

Structural changes in chlorine implanted poly(vinyl alcohol) films

Poly(vinyl alcohol) (PVA) films were implanted with chlorine ions in the fluence range of 10¹³-10¹⁶ ions/cm² on to PVA films of thickness 40 μm. FTIR spectroscopic study was carried out to see the structural changes. It was found that oxidation and carbonization progressively occurs in the film as a function of total fluence. The structural change occurs in the form of scission of C-C, C-OH and C-H bonds. SEM studies were carried out which revealed the surface defects in the form of cracks and etching. ESCA studies established that Cl⁺ ions get deposited on the surface. Changes in the crystallinity were observed from the X-ray diffraction studies. The implanted chlorine ions enhanced the electrical conductivity by the order of 10⁺² S/cm.     

Ion beam induced modifications in electron beam evaporated aluminum oxide thin films

Al₂O₃ thin films find wide applications in optoelectronics, sensors, tribology etc. In the present work, Al₂O₃ films prepared by electron beam evaporation technique are irradiated with 100 MeV swift Si⁷⁺ ions for the fluence in the range 1 × 10¹² to 1 × 10¹³ ions cm⁻² and the structural properties are studied by glancing angle X-ray diffraction. It shows a single diffraction peak at 38.2° which indicates the γ-phase of Al₂O₃. Further, it is observed that as the fluence increases up to 1 × 10¹³ ions cm⁻² the diffraction peak intensity decreases indicating amorphization. Surface morphology studies by atomic force microscopy show mean surface roughness of 34.73 nm and it decreases with increase in ion fluence. A strong photoluminescence (PL) emission with peak at 442 nm along with shoulder at 420 nm is observed when the samples are excited with 326 nm light. The PL emission is found to increase with increase in ion fluence and the results are discussed in detail.     

Electronic excitations induced modifications of structural and optical properties of ZnO-porous silicon nanocomposites

The influence of swift heavy ion (SHI) irradiation on structural and photoluminescence (PL) properties of ZnO nanocrystallites deposited into porous silicon (PS) templates by the sol-gel process was studied. The ZnO/PS nanocomposites were irradiated using 120 MeV Au ions at different fluences varying from 1 × 10¹² to 1 × 10¹³ ions/cm². The intensity of the X-ray diffraction peaks is suppressed at the high fluence, without evolution of any new peak. The PL emission from PS around 700 nm is found to decrease with increase in ion fluence, while the PL emission from deep level defects of ZnO nanocrystallites is increased with ion fluence. At the highest fluence, the observation of drastic increase in PL emission due to donor/acceptor defects in the region 400-600 nm and suppressions of XRD peaks could be attributed to the defects induced structural modifications of ZnO nanocrystallites.     

Lattice expansion and evolution of damage buildup in Be-implanted InAs

The lattice expansion in InAs single crystal, due to ion-implantation by 80 keV Be ions with the implantation fluencies ranging from 1 × 10¹² to 2 × 10¹⁶ cm⁻², has been investigated by using high resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM), and Rutherford backscattering spectrometry/channeling (RBS/C). In order to clarify the evolution of damage buildup, the nonlinear maximum perpendicular strain ε_m as a function of the Be fluence was obtained and analyzed. The curve of ε_m vs. Be fluence is subdivided into five regions, each having a different damage accumulation behavior. The involved probable mechanisms of microstructural variation in InAs due to Be implantation of different fluencies are analyzed in detail.     

Kr ion irradiation study of the depleted-uranium alloys

Fuel development for the reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium nuclear fuels that can be employed to replace existing high enrichment uranium fuels currently used in some research reactors throughout the world. For dispersion type fuels, radiation stability of the fuel-cladding interaction product has a strong impact on fuel performance. Three depleted-uranium alloys are cast for the radiation stability studies of the fuel-cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Al, Si)₃, (U, Mo)(Al, Si)₃, UMo₂Al₂₀, U₆Mo₄Al₄₃ and UAl₄. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200 °C to ion doses up to 2.5 × 10¹⁹ ions/m² (∼10 dpa) with an Kr ion flux of 10¹⁶ ions/m²/s (∼4.0 × 10⁻³ dpa/s). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.