bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crichtonite Structure Type (Am21O38 and A2M19O36) as a Host Phase in Crystalline Waste Form Ceramics
Authors: Gong W. L. , Ewing R. C. , Wang L. M. , Xie H. S. 
Published: April 2011

AbstractPrevious studies of ceramic crystalline waste forms, e.g. Synroc, tailored ceramics, and supercalcine, have concentrated on phases which are major constituents in the formulations: zirconolite, pyrochlore, hollandite, perovskite and zircon. These phases usually occur as members of multi-phase assemblages which are required for the incorporation of the wide variety of radionuclide elements present in the waste and the non-radioactive components added during reprocessing and pretreatment. The crichtonite structure (AM21O38 and A2M19O36), based on crystallo-chemical considerations and natural compositional analogues, may effectively incorporate both fission products and actinides. The naturally occurring crichtonite structure types include Sr (crichtonite), Ca and REE (loveringite), Na (landauite), REE and U (davidite), K (mathiasite), Ba (lindsleyite), and Pb (senaite), which are classified based on the dominant, large cations occupying the A-site. The crystal structure contains three types of sites of distinct size, from very large, M0, intermediate (M1, M3, M4, and M5), to small (M2). Numerous coupled substitutions within these cation sites allow for charge balance. Synthesis experiments were completed on the Ba-, Sr-, Ca-, and K-member compositions at 3 GPa and 1,150 °C. Low pressure synthesis should be possible, as natural minerals mostly occur in low-P systems. Reaction products were characterized by powder x-ray diffraction, scanning electron microscopy and electron microprobe analysis. In addition to the crichtonite phases, rutile, spinel, perovskite and armalcolite were identified as well. The Crichtonite structure type is estimated to accommodate waste loading of up to 30 wt. % PW-4B waste.
Comparison of Ceramic Waste forms Produced by hot Uniaxial Pressing and by Cold Pressing and Sintering
Authors: Oversby V. M. , Vance E.R. 
Published: April 2011

AbstractSynroc C waste form specimens prepared using the Australian-developed technology are uniaxially pressed in stainless steel bellows at 1200°C and 20MPa. This produces a material with high chemical and physical durability and with the radioactivity enclosed inside both the waste form and the bellows. An alternative method of producing the ceramic product is to use cold pressing of pellets followed by reactive sintering to provide densification and mineralization. Depending on the scale of waste form preparation required and on the activity level and nature of the waste streams, the cold press and sinter method may have advantages. To evaluate the effects of production method on waste form characteristics, especially resistance to dissolution or leaching of waste elements, we have prepared two simulated waste samples for evaluation. Both samples were prepared from liquid precursor materials (alkoxides, nitrates, and colloidal silica) and then doped with waste elements. The precursor material in each case corresponded to a basic phase assemblage of 60% zirconolite, 15% nepheline, 10% spinel, 10% perovskite, and 5% rutile. One sample was doped with 25% by weight of U; the other with 10% by weight each of U and Gd. Each sample was calcined at 750°C for 1 hr. in a 3.5% H2 in N2 atmosphere. Then one portion of each sample was hot pressed at temperatures ranging from 1120 to 1250°C and 20MPa pressure in steel bellows. A separate portion of each sample was formed into pellets, cold pressed, and sintered in various atmospheres at 1200°C to produce final products about 2/3 cm in diameter. Samples were then examined to determine density of the product, grain sizes of the phases, phase assemblage, and the location of the U and Gd in the final phases. Density data indicate that sintering gives good results provided that the samples are held at 200°C for long enough to allow trapped gases to escape.
Synthetic Melted Rock-Type Wasteforms
Authors: Sobolev Igor A , Stefanovsky Sergey V , Lifanov Fyodor A 
Published: April 2011

AbstractGlass-ceramic materials based on sphene, pyroxenes, apatite as well as various SYNROC formulations have been produced through melting in a laboratory electrically-heated furnace and inductive-heated melter (“cold crucible”). Materials prepared were investigated by X-ray diffraction analysis, electron-probe microanalysis, infra-red and EPR spectroscopies. Basic properties such as leach rates of radionuclides, density and compressive strength have been determined. Melted SYNROC-B and C phase compositions produced by induction melting are similar to hot-pressed SYNROC.
pH Dependence of the Aqueous Dissolution Rates of Perovskite and Zirconolite at 90°C
Authors: McGlinn Peter J , Hart K. P. , Loi E. H. , Vance E. R. 
Published: April 2011

AbstractPerovskite and zirconolite are two of the major phases of the Synroc titanate mineral assemblage. Their aqueous durability under a range of pH conditions at 90°C has been examined. Solution analysis, electron microscopy and X-ray diffraction have been used to investigate the dissolution behaviour of these phases, and a perovskite phase doped with Nd, Sr and Al, using buffered solutions at pH levels of 2.1, 3.7, 6.1, 7.9 and 12.9. After 43 days of leaching, Ca and Ti extractions from perovskite and zirconolite show only a weak pH-dependence.SEM investigation of the samples leached at pH 2.1, 6.1 and 12.9 showed that a titanaceous surface layer formed on the perovskite specimens. XRD analysis of the perovskite samples showed that anatase formed on the leached surface at acidic and neutral pHs, but not under alkaline conditions, and that minor amounts of rutile also formed. In the leached perovskite specimens doped with Nd, Sr and Al, no rutile was found by XRD and anatase was only detected in the sample leached at pH 2.1. There were no detectable changes in the leached zirconolite samples examined by SEM and XRD.
Surface Alteration of Sintered Product of Strontium Aluminum Silicate Under Hydrothermal Conditions
Authors: Mimura H. , Koyama A. , Akiba K. 
Published: April 2011

AbstractThe surface alteration of strontium aluminum silicate has been studied under hydrothermal conditions in connection with the leachability of Sr from solidified radioactive wastes. Samples exposed to a 3 M NaCl solution at 300°C produced a precipitated layer of analcime (NaAISi2O6) with high crystallinity. The normalized leach rates for Sr in 3 M NaCl and 3 M KC1 solutions were found to be less than 10-3 g/cm2.d, yielding high resistance to leaching in these solutions.On exposure to the CaCl2 solution at 300°C, anorthite (CaAl2Si2O8) was formed on the surface, indicating the replacement of Sr with Ca through isomorphous substitution. In the case of MgCl2 solution, a thick precipitated layer of clinochlore (Mg5Al(Si3Al)O10(OH)8) built up on the outermost surface. This layer serves to depress the migration of Sr, resulting in the deposition of SrCl2 salts in the altered layer.
Macro and Micro Observations on Mortar Alteration Mechanism Under the Various Solution Conditions
Authors: Fujiwara A. , Tashiro S. , Takemura T. , Sakogaichi K. , Yokomoto S. , Katsuyama K. 
Published: April 2011

AbstractAccelerated aging tests have been conducted to evaluate the long-term durability of cementitious material against aggressive ions. In tests, cementitious specimens were immersed in the solutions containing concentrated aggressive ions at high temperature and it promoted diffusion of the ions in the specimen. This method would be suitable for the evaluation on the aging as the alteration of the specimen would be expected to resemble the natural behavior. This paper presents a classification of alteration mechanism in the immersion tests using MgCl2 and Na2SO4 solution. This classification was done by relating the changes of compressive strength to microscopic and mineralogical changes.
Influence of Aggressive Liquid Environment on the Physico-Chemical and Mechanical Characteristics of Mortar-Radwaste Mixture Form
Authors: Perić Aleksandar D , Plećaš Ilija B , Pavlović Radojko S 
Published: April 2011

AbstractMortar was used as a matrix material in an immobilization process of radioactive waste material, 137CsCl solution, where the final product had a water-to-cement ratio of 0.36. Solidified orthocylinder shaped samples, H=4.5 cm, with the exposed surface area completely open to contact leachant medium, were used in prospecting physico-chemical and mechanical characteristics of mortar-radwaste mixture forms. After curing period of 28 days in an atmosphere of defined parameters, samples were introduced to leaching in the specific leachant media. Leachants were chosen up to their aggressive influence on matrix material deterioration and decomposition: distilled water, chloride and sulphate solutions. Experiments were performed for 730 days and the 137Cs cumulative leached fraction for each leachant was calculated. Leach-rate steady-state values were obtained after approximately 290 days. The same trend in obtaining saturation value was noticed in an investigations of pH value and Ca2+ concentration in the three groups of leachants, due to a Ca2+ depletion from the matrix structure. Mortar-radwaste mixture samples were withdrawn from the leaching experiments and investigated on their mechanical strength. Mechanical strength characteristics adopted a decreasing trend for the samples treated in leachants longer than 100 days, which continued in the two years period of experimental duration.
The Use of Surface Analytical Techniques to Measure the Loadings of Uranium and Plutonium Sorbed Simultaneously from Solution onto Rocks
Authors: Berry J A , Bishop H E , Cowper M M , Fozard P R , McMillan J W 
Published: April 2011

AbstractSmall polished blocks of granite, diorite and dolerite were immersed in solutions containing uranium and plutonium at equal initial concentration. The samples were analysed by the advanced surface analytical techniques of secondary ion mass spectrometry (SIMS) and nuclear microprobe analysis. The results show that both actinides sorb onto the same minerals in the three rocks. However, SIMS data show that significantly more uranium was sorbed than plutonium.
Influence of Microbial Activity on Technetium Behaviour in Soil Under Waterlogged Condition
Authors: Tagami K. , Uchida S. 
Published: April 2011

AbstractThe behaviour of Tc in soil depends upon its chemical forms. Under aerobic conditions, Tc is present as pertechnetate Tc+7(TcO4–), which has a high geochemical mobility and bioavailability. However, the form changes through a combination of factors such as redox conditions and microbial activity in soils. The anaerobic condition can be supplied in waterlogged rice paddy soil, which is common to Japan and other Southeast Asian countries.In this study, we focused on the influence of microbial activity on Tc behaviour in soil under the waterlogged condition. The microbial activity is expected to be controlled by addition of glucose and the activity causes a change in the soil redox condition. Air-dried soil with increasing glucose contents and sterile soil were used to compare the effect of microbial activity. The soils were waterlogged with99Tc solution. Although the concentrations of99Tc in the surface and bottom solutions of air-dried soils decreased over time with increasing glucose concentration, those of sterile soils were almost constant during the experiment. From these results, it was assumed that the activity of microorganisms influenced Tc adsorption onto the soil.
Sorption Behavior of Uranium(VI) on a Biotite Mineral
Authors: Idemitsu K. , Obata K. , Furuya H. , Inagaki Y. 
Published: April 2011

AbstractBiotite has the most important role for the sorption of radionuclides in granitic rocks. Experiments on the sorption of uranium (VI) on biotite were conducted to understand the fundamental controls on uranium sorption on biotite mineral, including the effects of pH and uranium concentration in solution. Biotite powder (mesh 32 – 60) were washed with 1N HC1 for a week and were rinsed twice with deionized water for a week. This HC1 treatment was necessary to avoid the effects by other minerals. The agreement between surface adsorption coefficient, Ka, of both biotites with and without HC1 treatment was within one order of magnitude. The peak Ka value was in the range of 0.1 to 0.01 cm3/cm2 around pH 6. A comparison of aqueous uranium speciations and sorption results indicates that neutral uranyl hydroxide could be an important species sorbed on the biotite.Sequential desorption experiments with KC1 and HC1 solutions were also carried out after sorption experiments to investigate sorption forms of uranium. Approximately 20 % of uranium in solution were sorbed on the biotite as an exchangeable ion. The fraction of exchangeable uranium had a little dependence on pH. The other uranium could not be extracted even by 6N HC1 solution. It is possible that most of the uranium could be precipitated as U(IV) via Fe(II) reduction on the biotite surface.
Influence of Humic Acid on Sorption of Neptunium(V) onto Soil
Authors: Sakamoto Y. , Nagao S. , Ohnuki T. , Senoo M. , Ohashi A. , Sato S. , Ohashi H. 
Published: April 2011

AbstractThe pH dependence of the stability constant of Np(V)-humate and the sorption of Np(V) onto soil was studied to clarify the influence of dissolved organic carbon on the migration behavior of Np(V) in soil layer. The stability constant of Np(V)-humate was expressed by logβ1=(0.35 ±0.03)pH+0.04±0.01 in the pH region from 5.3 to 8.7, and the intrinsic stability constant by logβ*1=3.66±0.05.The sorption of Np(V) increased with pH up to pH 7, and tended to reach maximum, about 95%, at pH 9 in the absence of humic acid. In the presence of humic acid more than 140mg/l, the sorption of Np(V) was lower than that in the absence of humic acid above pH 7, while any influence of humic acid on the sorption of Np(V) onto soil was not observed below pH 7. The sorption behavior of Np(V) onto soil was explained by reversible sorption of NpO2+and sorption of NpO2CO3- and/or NpO2OH. Further, the influence of the size distribution of Np(V) on the sorption onto soil was examined and discussed.
Formation of Silicon on Insulator (Soi) With Separation by Plasma Implantation of Oxygen (Spimox)
Authors: Liu J.B. , Iyer S.S.K. , Min J. , Chu P. , Gronsky R. , Hu C. , Cheung N.W. 
Published: April 2011

AbstractBuried oxide layers in Si were fabricated using non-mass analyzed plasma immersion ion implantation (PHI). We call this process of making separation by implantation of oxygen (SIMOX) with implantation by PIII as separation by plasma implantation of oxygen (SPIMOX). The implantation was carried out by applying a large negative bias to a Si wafer immersed in an oxygen plasma and a nominal dose of 2 × 1017 cm”2 of oxygen was obtained in less than three minutes. Cross section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) were used to characterize the wafers. Three distinct modes of microstructure development were observed after post implantation annealing. With a low oxygen dose (< 1 × 1017 cm”2 ), isolated silicon dioxide precipitates did not grow large enough to form a continuous oxide layer. With a high oxygen dose ( > 3 × 1017 cm”2 ), however, a single buried oxide layer was observed. By optimizing the concentration ratio of 0+ and 02+ in the plasma and the implant dose, a double oxide layer (Si/oxide/Si/oxide/Si) structure, was produced in a single implantation step.
Erbium Doping of Silicon and Silicon Carbide Using Ion Beam Induced Epitaxial Crystallization
Authors: Boucaud P. , Julien F.-H. , Lourtioz J.-M. , Bernas H. , Clerc C. , Chaumont J. , Bodnar S. , Regolini J.-L. , Lin X. W. 
Published: April 2011

AbstractErbium doping of silicon and silicon carbide using implantation followed by ion beam induced epitaxial crystallization (IBIEC) is investigated. The implanted concentration of Er was 1.4 at% in both cases. In Si(100), Rutherford backscattering/channeling revealed that about 40% of the Er atoms evolved upon rapid thermal annealing from an undetermined position (room temperature) to an interstitial tetrahedral position (650°C) and finally to a substitutional position (950°C). The remaining Er atoms were presumably trapped in the small precipitates visible in high resolution transmission electron microscopy. The photoluminescence at 1.54 μπι of Er3+ is enhanced with annealing and persists up to room temperature after a 950 °C 1 min anneal. The high concentration of optically active Er atoms is illustrated by the lack of saturation of the photoluminescence at high pumping excitation intensity. Erbium was also implanted into cubic silicon carbide films prepared by chemical vapor deposition on Si at 900 °C. Both solid phase epitaxy (SPE) and IBIEC were performed. After a 950°C anneal, the low temperature photoluminescence at 1.54 μιη after IBIEC was five times higher in SiC than in silicon. The difference in photoluminescence linewidth between IBIEC (broad lines) and SPE (sharp lines) is explained in terms of interactions between optically active erbium atoms.
Characterization of Si Implantation and Annealing of InP by Raman Spectroscopy
Authors: Artus L. , Cusco R. , Martin J.M. , Gonzalez-Diaz G. 
Published: April 2011

AbstractRaman scattering was used to assess the lattice damage caused by Si+implantation in InP, as well as the lattice recovery achieved after rapid thermal annealing (RTA). Semi-insulating InP was implanted with Si+with doses in the range of 1012to 5xl014cm”2. Raman scattering measurements show a progressive intensity reduction of the characteristic first- and second-order InP Raman peaks and an enhancement of the disorder activated modes with increasing dose. The onset of amorphization was found to be at about 1014cm”2. RTA of the implanted samples at 875 °C for 10s results in a very good recovery of the InP lattice even for the highest dose, as confirmed by Raman scattering measurements.
Atom Penetration from A Thin Film into the Substrates During Sputtering by Polyenergetic Ar+ Ion Beam with Mean Energy of 9.4 keV
Authors: Kalin B.A. , Gladkov V.P. , Volkov N.V. , Sabo S.E. 
Published: April 2011

AbstractPenetration of alien atoms (Be, Ni) into Be, Al, Zr, Si and diamond was investigated under Ar+ ion bombardment of samples having thermally evaporated films of 30-50 nm. Sputtering was carried out using a wide energy spectrum beam of Ar+ ions of 9.4 keV to dose D=lxl0 -10 ion/cm2. Implanted atom distribution in the targets was measured by Rutherford backscattering spectrometry (RBS) of tT and He+ ions with energy of 1.6 MeV as well as secondary ion mass-spectrometry (SIMS).During the bombardment, the penetration depth of Ar atoms increases with dose linearly. This depth is more than 3...20 times deeper than the projected range of bombarding ions and recoil atoms. This is a “deep action” effect.The analysis shows that the experimental data for foreign atoms penetration depth are similar to the data calculated for atom migration through the interstitial site in a field of internal (lateral) compressive stresses created in the near-surface layer of the substrate as a result of implantation. Under these experimental conditions atom ratio r/rm (r¡ - radius of dopant, rm - radius target of substrate) can play a principal determining role.
Study of Titanium Nitrides Synthesized by High Dose Ion Implantation
Authors: Guemmaz M. , Mosser A. , Raiser D. , Grob J.J. , Cornet A. , Paletto S. 
Published: April 2011

AbstractPolycrystalline titanium samples were implanted with N+ ions at high fluences and at several energies. The aim was to obtain 4000 Â thick nitrided layers of constant nominal concentration equal to 20% ,30%, and 40%.The results obtained by RBS showed a flat nitrogen distribution with depth and the measured concentrations were respectively 20%,31% and 38%.X-ray grazing incidence diffraction indicated that, at 20%, a nitrogen solid solution is formed in the a-Ti matrix. At 31% the nitrogen solid solution is present besides a 5-TiN phase and at 38% only the 5-TiN phase remains.From nanoindentation measurements, we derived the depth-related hardness and Young's modulus of the implanted samples. These values were compared to those found on titanium nitride layers obtained with other coating techniques.
Implantation of Metal Ions into High Speed Steel for Improved Tribology
Authors: Ruck D.M. , Hirvonen J.-P. , Yan S. , Lappalainen R. , Torrfi P. 
Published: April 2011

AbstractHigh speed steel with a martensitic microstructure is widely used in tool industry, but often the usage is limited by severe abrasive and corrosive wear. Metal ion implantation is a promising method to improve the tribological behaviour of this steel, as was shown in several publications. In this paper we discuss the application V and Cr implanted high speed steel, both of these elements are alloying constituents of the steel matrix. Combined with implantation of carbon is also carried out.The tribological tests were performed with a pin-on-disc machine under dry sliding conditions. The obtained tribological results are discussed in relation to the microstructures of the nonimplanted and implanted samples.
Effects of Implantation Temperature on the Structure, Composition and Oxidation Resistance of Sic
Authors: Yang Zunde , Du Honghua , Libera Matthew , Singer Irwin L. 
Published: April 2011

Abstractɑ-SiC crystals were implanted with aluminum to a high dose at room temperature or 800°C. Studies by transmission electron microscopy showed that SiC was amorphized by room temperature implantation but remained crystalline at 800°C. Crystalline aluminum carbide was formed and aluminum redistribution took place in SiC implanted at 800°C. Implanted and unimplanted crystals were oxidized in 1 atm flowing oxygen at 1300°C. Amorphization led to accelerated oxidation of SiC. The oxidation resistance of SiC implanted at 800°C was comparable to that of pure SiC. The oxidation layers formed on SiC implanted at both temperatures consisted of silica embedded with mullite precipitates. The phase formation during implantation and oxidation is consistent with thermodynamic predictions.
Effect of Oxygen Implantation on the Electrochemical Properties of Palladium
Authors: Fujihana Takanobu , Ueshima Masato , Takahashi Katsuo , Iwaki Masaya 
Published: April 2011

AbstractThe electrochemical properties of O+-implanted Pd measured by cyclic voltammetry in a 0.25 mol dm-3 H2SO4 solution were investigated in relation to their composition and structure. Implantation of 16O+ was performed with doses between 1O17 and 1O18 ions cm-2 at 150 keV, and at nearly room temperature. SIMS, ERD combined with RBS, and XRD were used to analyze the composition depth profile and structure of O+-implanted Pd surface layers. The H atoms were accumulated with a gaussian distribution and carbon materials containing the solid solution of PdCx (x=0.13-0.15) were also formed in the near surface layers during O+-implantation. The distribution of implanted oxygen changed from gaussian to trapezoidal as the dose increased, accompanied by the crystal growth of Pd(OH)2, and simultaneously, the amount of accumulated H atoms increased. The voltammetric measurements revealed that with an increase in the dose, the hydrogen absorption was suppressed at the early stage of sweep cycles, and at the final stage, the redox reaction of both hydrogen and Pd was activated. From these results, we propose that the carbon materials containing the PdCx formed during O+-implantation suppress the hydrogen absorption, and the metallic Pd like a Pd-black formed by the reduction of Pd(OH)2 during voltammetric measurements causes the electrochemical activation of O+-implanted Pd.