Synchrotron radiation glancing incidence X-ray diffraction: a tool for structural investigations of ion implanted glasses

The availability of very intense and highly collimated synchrotron radiation beams coupled with the glancing incidence geometry makes possible to study ion implanted glasses with X-ray diffraction. We maximize the contribution to the scattering of the metal-rich (clusters) layer by working at the critical angle for total external reflection at the implanted layer-substrate interface. By using the refracted beam as a probe the diffraction profile of the metallic clusters in very diluted samples (a single implant in the 10¹⁶ at/cm² range) can be extracted. We report some results on SiO₂ glasses implanted with Cu and Ni. We used a very intense monochromatic 10(h) × 24(v) μm² beam from an undulator source. The data were collected by using an imaging plate (IP) system with integration times in the order of minutes. From the azimuthal integration of the images the clusters diffraction pattern can be extracted enabling crystalline phases identification, the retrieval of the lattice parameters and in some cases the determination of the clusters sizes.     

Helium irradiation of Ni-(Zr or Nb) metallic glasses: Blistering,flaking and bubble formation

NiZr and NiNb are potential metallic glasses for nuclear applications. We have studied blistering, flaking and bubble formation in Ni₆₄Zr₃₆, Ni₃₃Zr₆₇ and Ni₆₀Nb₄₀ glasses under helium ion bombardment at room temperature. The effect of projectile energy (50–150 keV), total dose (0.01–10 × 10¹⁸ ions/cm²), dose rate (10–100 μA/cm²) and thermal crystallization on critical dose for blistering and/or flaking, average blister diameter and development of surface topography was examined. The surface damage effects in metallic glasses were in general similar to those for crystalline materials with the notable exception that the critical dose values are higher by about 50–100% for metallic glasses. TEM investigations revealed irradiation induced partial crystallization of Ni₃₃Zr₆₇ glass. Metallic glasses Ni₆₄Zr₃₆ and Ni₆₀Nb₄₀ were stable under helium irradiation and have also shown very high resistance against blistering and/or flaking. The possible mechanisms of helium trapping in metallic glasses are also discussed.     

The effect of lattice and grain boundary diffusion on the redistribution of Xe in metallic nuclear fuels: Implications for the use of ion implantation to study fission-gas-bubble nucleation mechanisms

A multi-atom gas bubble-nucleation mechanism has been proposed as part of a predictive fission-gas release model for metallic nuclear fuels. Validation of this mechanism requires experimental measurement of fission-gas bubble-size distributions at well-controlled gas concentrations and temperatures. There are advantages to carrying out such a study using ion implantation as the source of gas atoms compared with neutron irradiations. In spite of previous successes using ion implantation to study fission-gas behavior in oxide fuels, there is significant uncertainty about the efficacy of using ion beams for metallic fuel studies. To address the question of the applicability of ion beams in experiments designed to study fission-gas behavior in metallic fuels, we developed and applied an exact model for the redistribution of implanted ions under annealing conditions. The conclusion is that, given the assumptions, the results from implantations at 1 MeV or less may be overwhelmed by the surface effects at all relevant temperatures. Implanting at 10 or 80 MeV can significantly diminish the influence of the surfaces and the steep concentration gradients. At 80 MeV, the location of the peak concentration profile remains stable with annealing time. Thus, it appears that ion implantation can be an appropriate tool to study the size distribution of Xe bubbles in metallic fuels. Of the conditions investigated, the best for the study are to implant at 80 MeV and carry out anneals at 773 K, 873 K, and 973 K for times less than 10,000 s.     

Environment and oxidation state of molybdenum in simulated high level nuclear waste glass compositions

Alkali borosilicate glasses containing between 20 and 35 wt% of a simulated high level nuclear waste stream with varying Li₂O contents were melted under neutral (air) and reducing (nitrogen/hydrogen) conditions. XRD analysis of the as-cast glasses showed a tendency for the products to remain amorphous when melted under neutral conditions and for metallic silver to develop in the reduced melts. EXAFS analysis revealed (MoO₄)²⁻ tetrahedra in all glasses regardless of the sparge applied during melting. The glasses were heat treated to simulate an interruption to the cooling system used to prevent heat build-up in the vitrified product store. Powellite-type molybdate phases were found to develop in the heat treated samples and formed at lower waste loadings in glasses sparged with a reducing gas. A reduction in the quantity of Li₂O lead to a reduction in the quantity of powellite-type molybdate phases. EDS showed the primary molybdate phase to be high in Sr and rare earth elements and TEM indicated that the presence of silver metal encouraged molybdate formation.     

Effects of ion irradiation in metallic glasses

Application of metallic glasses as structural materials has been limited by their poor ductility. To overcome brittle failure, nanocrystals are intentionally introduced to stabilize the glasses. In this study, we report on the application of ion irradiation to induce nanocrystalization in a Cu₅₀Zr₄₅Ti₅ (CZT) alloy. Transmission electron microcopy, microindentation and nanoindentation have been used to characterize the CZT alloy irradiated with 140 keV He ions at room temperature. Hardness enhancement was observed near the projected range of the He ions, coinciding with the formation of nanocrystals. Such microstructural changes, however, were not observed in the near surface region, where the electronic stopping process is dominant.     

Magnetic behavior of Ni+ implanted silica

Ni⁺ has been implanted in amorphous silica layers and silica glasses at two dose levels (10¹⁶ and 10¹⁷ Ni⁺ cm⁻²) and two different energies (30 and 160 keV). Superparamagnetic and ferromagnetic behaviors were observed with a SQUID magnetometer at RT and 5 K, respectively. Using Langevin’s theory, the size of the metallic nanoparticles were deduced to ranges between 2 and 6.5 nm in good agreement of HRTEM observations. The E′ type center and the neutral oxygen vacancy (NOV) defects were observed by UV–Vis absorption. Finally, in samples annealed at 600°C under Ar or Ar + H₂ atmospheres two different phenomena were observed: the reduction of Ni²⁺ to Ni⁰ and the elimination of defects introduced by implantation.     

聚乙烯醇基可剥离膜去除不锈钢表面放射性污染的研究

针对放射性热室去污难点，以聚乙烯醇（PVA）作为成膜基材，添加改性淀粉等成分制备可剥离膜涂料，通过改变成膜环境温度及模拟污染液pH值和初始浓度，研究了可剥离膜的稳定性及其对ASUS304钢板表面污染物的施工适宜性和去污性能。结果表明，聚乙烯醇基可剥离膜涂料具有良好的施工性和可剥性，对金属表面单一铀污染物和混合污染物（含钴、锶、铀）的去污率均大于90%。在工装配合下对热室进行去污，取得了极佳的效果，表明本文所研制可剥离膜涂料可用于热室或核设施金属表面的放射性污染去污。     

惯性约束聚变靶材料掺杂技术综述

文章概要综述了惯性约束聚变掺杂靶材料的制备方法，内容包括聚苯乙烯掺卤素和过渡金属元素，玻璃与塑料掺簇粒子，以及塑料涂层掺高Ｚ金属等。简述了掺杂材料的分析测试手段及其在ＩＣＦ中的应用。     

Study by PIXE method of trace elements transferred from prostheses to soft tissues and organs

Some metallic prostheses inserted in human hip undergo physico-chemical modification, a few years after their implantation. Tissues surrounding these prostheses are damaged by metallic element transfer. Surgeons in Clermont-Ferrand Hospital (France) recover tissues of abnormal coloration that were in contact with metallic implants. PIXE technique (particles induced X-ray emission) with a 400 μm proton beam and 3 MeV of energy is an efficient technique to analyze these tissues and to detect elements, which are transferred from prosthesis to tissues. PIXE analyses were carried at the CERI-CNRS Laboratory. We have applied this method to determine qualitatively and quantitatively trace elements migration from metallic implants to surrounding tissues and organs, like kidney, spleen, liver, lymphatic gland and lung.     

陶瓷真空室研制及其阻抗的研究

介绍了电子储存环注入凸轨击磁铁及春真空室常采用的几种技术方案。合肥电子储存环新凸轨注入系统选择了铁氧体磁铁内置陶瓷真空室的方式。为了同时满足脉冲磁场穿透性能及束流耦合阻抗的要求，陶瓷真空室的内壁须镀１层金属薄膜。     

Facies of ion bombarded surfaces

Observations made in the optical examination of a variety of brittle materials subjected to bombardment by 140 keV protons, deuterons, and helium ions are summarized. Among the materials studied were commercial glasses, carbides, oxides, silicon nitride, titanium boride, and carbon. In most cases, when swelling occurred, it was by the introduction of porosity. The radiation blistering appeared to take place by fracturing in the porous layer under surface stress rather than by plastic deformation under the gas pressure of segregated implanted gas.     

X-ray absorption studies of bismuth valence and local environments in borosilicate waste glasses

X-ray absorption spectra (XAS) were collected and analyzed to characterize bismuth (Bi) environments in borosilicate glass formulations developed for the immobilization of high level nuclear wastes (HLW), from the bismuth phosphate process. Therefore, the structural role of Bi in these glasses is of interest; in addition in the present study, more particular interest in Bi originated from unusual foaming that was observed during melt cooling, where it was initially suspected that Bi³⁺ reduction to Bi⁰ may generate oxygen that caused the foaming. Observations from scanning electron microscopy of some HLW glass samples indicated a Bi-phosphate association. Bi L_III XAS of 13 Bi-containing waste glass formulations of various compositions were measured that exhibited varying degrees of melt foaming. The Bi XAS are similar for all glasses investigated, and indicate Bi³⁺O₃ nearest-neighbor environments with Bi–O distances near 2.13 Å. This environment is similar to the most localized Bi coordination characteristics in the crystalline Bi-silicates, eulytite (Bi₄Si₃O₁₂) and bismutoferrite (BiFe₂Si₂O₈OH). However, the Bi-environments in the glasses are distinctly different from the Bi-site in crystalline BiPO₄; therefore, XAS indicates no evidence of Bi-phosphate domains in the glasses measured. No XAS evidence was observed in any of the glasses investigated for Bi clustering, such as metallic Bi, or Bi–O–Bi bonding. Since the local Bi environments look similar for all glasses investigated, Bi XAS data and analyses show no association of the melt foaming problems with changes of Bi environments in the corresponding glass. The foaming may be dependent on chromate or phosphate behavior in the glass structure.     

EXAFS study on Ag-doped silicate glasses irradiated with low-mass ions

We present an EXAFS study on Ag-doped soda-lime glass waveguides obtained by ion-exchange and treated by low-mass ion-irradiation to promote the formation of metallic clusters. For differently prepared samples we have determined the Ag local order before and after the treatment. In the as-exchanged glasses Ag is coordinated with O at a distance significantly shorter than the Na---O bond length in the unexchanged glass. In irradiated samples we found the formation of metal aggregates. Structural parameters of clusters in high-temperature irradiated sample are compatible with a compressed fcc structure while in room-temperature irradiated specimen a more complicated structure comes out.     

Pitting and EPR studies of ion implanted plain and sensitized 304 stainless steel

30 keV N₂⁺, Ti⁺ and N₂⁺ followed by Ti⁺ ions were implanted at room temperature on plain and sensitized 304 stainless steel (304 SS) foils. The ion fluences ranged from 1 × 10¹⁷ ions/cm² to 5 × 10¹⁷ ions/cm². Pitting studies in quiescent non-dearated 3.5 wt.% NaCl electrolyte and Electrolytic Potentiokinetic Reactivation (EPR) studies in a standard electrolyte of KSCN + H₂SO₄ were carried out on plain, sensitized and implanted plain, and sensitized 304 SS foils. In general, the localized corrosion behaviour deteriorated on implantation in plain 304 SS irrespective of the nature of the implant species and their fluences employed in this work. However, the localized corrosion behaviour of implanted sensitized 304 SS showed an improvement. The benefits accrued was dependent on the nature of the implant species and their fluences. An attempt has been made to explain why the implant species interact differently, with the consequent difference in the localized corrosion behaviour, when the stainless steel substrate is in the sensitized state.     

Swelling and stacking fault formation in helium implanted SiC

Effects of annealing on surface swelling in helium implanted 4H-SiC were studied for different implant conditions. The significant increase of surface swelling observed upon high temperature annealing of samples implanted under severe implant conditions (high temperature and fluence) is observed to be concomitant with the growth of cavities and the formation of other extended defects in the highly damaged zone. Frank loops resulting from the drift of interstitials only form in the highly damaged zone. These loops promote the formation of Shockley partial dislocations leading to stacking fault pile-up. For less severe conditions of implantation, low temperature and fluence, the formation of dislocations is avoided upon post-annealing, and the recovery of swelling progressively occurs. Under intermediate conditions of implantation, the compensation between elastic recovery of the implantation-induced strain and the limited formation of cavities and interstitial-type clusters result in a constant swelling.     

Blistering,flaking and bubble formation in metal-metalloid metallic glasses bombarded with helium ions

The blistering and flaking behaviour of metallic glasses Fe₈₀B₂₀, Fe₄₀Ni₄₀B₂₀, Fe₄₀Ni₄₀P₁₄B₆ and Fe₄₀Ni₃₈Mo₄B₁₈ under helium ion bombardment at room temperature has been investigated. A trend of continuous layer-by-layer surface erosion of metallic glasses due to repetitive exfoliation was observed. Results as a function of projectile energy (50 keV ? E ? 150 keV) and helium current density (10–100 μ/cm₂) showed that the critical dose and the blister size dependence on these parameters is similar to crystalline solids. However, unlike in crystalline materials, cold work of Fe₄₀Ni₄₀P₁₄B₆ to 30% thickness reduction did not seem to affect the surface erosion behaviour. A comparative study of the same alloy Fe₄₀Ni₄₀P₁₄B₆ in amorphous and thermally crystallized forms showed about 50% higher resistance against blistering for the former. Microstructural investigations revealed helium bubble formation as a precursor stage to blistering but irradiation-induced partial crystallization was not observed for these metallic glasses.     

Swelling of refractory materials and silicate glasses on proton,deuteron, and helium ion bombardment

Small areas of polished plates were bombarded with 140 keV ions at room temperature, and the heights of steps formed at the edges of the bombarded areas were measured interferometrically. The refractory materials swelled because of porosity caused by the implanted gas. Vitreous silica and Pyrex did not. All the other glasses swelled when bombarded with protons or deuterons, but only dense barium crown swelled appreciably under helium ion bombardment.     

Plasma processing: a novel method to reduce the transient enhanced diffusion of boron implanted in silicon

In this paper a novel method is presented, based on the use of plasma processing, to suppress the transient enhanced diffusion of boron implanted in silicon. We found for silicon samples processed with plasma and subsequently boron implanted that the anomalous diffusion of the dopant atoms at the beginning of the annealing process is almost completely suppressed. This phenomenon is interpreted in terms of capture of the ion beam generated interstitials by the dislocations induced by the plasma processing. At room temperature the dislocations are observed to grow in size after the boron implant, attesting their efficiency as trapping centres for interstitials. Moreover, varying the plasma process conditions we can establish a general relation between the presence of the trapping centres induced by the plasma processing and the suppression of the transient diffusion.     

Patterned metallic coating of a ceramic chamber in storage ringbump magnets

To permit the pulsed field of a bump magnet to penetrate the vacuum chamber of a particle storage ring, a section of ceramic chamber is used. A thin metal coating on the inner surface is usually employed to prevent the static charge build-up on the surface of the ceramic chamber, as well as to reduce the coupling impedance. The metal coating, however, can lead to heating of the chamber walls due to eddy current. To avoid such an unwanted effect, a patterned coating is employed. In this paper, we discuss the electrical power and the field distortion due to the eddy current and the effect of various patterned metallic coatings on the motion of a circulating beam. The results are applied to the storage ring of the Pohang Light Source     

Electronic energy-density effects in ion tracks of metals

High resolution Auger-electron spectroscopy has been applied to the interaction of swift heavy ions with atomically clean metallic solids. Spectra have been taken for fast projectile electrons and for charge-state equilibrated ions at normal incidence on microcrystalline beryllium samples, Al(1 0 0) single crystals and several metallic glasses (Al₈₇La₇Ni₅Zr₁, Ni₇₈B₁₄Si₈, Co₆₆Si₁₆B₁₂Fe₄Mo₂). From the energy shift and from the Auger-line width we have extracted ion-track potentials and also electron temperatures inside ion tracks. A first determination of the angular distribution of multiple-ionization lines is presented as well.