bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sorption-Reagent Method in Liquid Radioactive Waste Management
Authors: Avramenko Valentin A. , Zheleznov Veniamin V. , Kaplun Elena V. , Marinin Dmitri V. , Sokolnitskaya Tatiana A. , Yukhkam and Anna A. 
Published: April 2011

ABSTRACTMethods of liquid radioactive waste (LRW) decontamination from radionuclides including their co-precipitation at specific conditions or adsorption on selective sorption materials are well known and extensively used in LRW management technologies. At the same time, it was shown in a number of papers that some forms of organic and inorganic ionexchangers react with solutions containing specific components that results in formation of virtually insoluble precipitates inside the sorbent matrix or on its surface. Here in some cases the sorbent selectivity to some radionuclides increases substantially.The sorption-reagent materials synthesized for decontamination purposes are the most highly selective in regard to such difficult to remove radionuclides as strontium-90 and cobalt-60. It was shown by comparative analysis of radionuclide removal efficiency by traditional selective sorbents and developed sorption-reagent materials that the latter have the highest distribution coefficients in systems too complex for “pure” sorption/ion-exchange decontamination. For example, the sorption-reagent materials have strontium distribution coefficients several dozens higher than those of commercially available sodium titanates and silicotitanates.The mechanism of radionuclide sorption on sorption-reagent materials of different types was studied. It was shown that this is a multi-stage process and the course of different stages of chemical reactions and sorption is determined by the parameters of medium from which radionuclides are sorbed. It was also shown that these materials application in liquid radioactive waste management enables one to develop simple technological setups combining the advantages of sorption and precipitation methods.One of the main fields of the sorption-reagent materials application can be decontamination of high-salinity radioactive waste formed whether as a result of ionexchanger filters regeneration in LRW management systems or in reverse osmosis installations. Use of sorption-reagent materials for high-salinity waste management enables one to reduce several ten-fold or even hundred-fold the volume of solid radioactive waste (SRW) to be sent for final disposal and, therefore, to decrease the cost of LRW management. The approach consisting in combined application of reverse-osmosis and sorption-reagent methods for LRW decontamination is suggested.
General Approach Used in the Performance Assessment for the Waste Isolation Pilot Plant
Authors: Rechard Rob P. 
Published: April 2011

ABSTRACTThis paper discusses the technical approach and rationale of the performance assessments (PAs) conducted for the Waste Isolation Pilot Plant that contributed to the success of the certification in 1998. The PAs were iterated: there were four preliminary PAs between 1989 and 1992 and the certification PA in 1996. Although many changes occurred between the 1992 PA and 1996 PA, the preliminary iterations provided a strong foundation on quality assurance, parameter and model databases, documentation, and peer review. The seven general steps of a PA are used to provide a brief overview of their history. The paper then delves into the rationale used for the most computationally intense step of a PA, the consequence evaluation. For this evaluation, Sandia National Laboratories mostly used detailed models when evaluating the probabilistic performance of the repository under the stylized conditions specified by the U.S. Environmental Protection Agency (EPA). A computational tool, CAMCON, was specifically tailored for this approach. Many advantages were gained by using detailed models directly in the PA, rather than using simplified results of these models. One important advantage was that models and parameters remained fairly unbiased (i.e., the analysis had only a few major conservative assumptions rather than many, unquantified conservatisms). This approach allowed Sandia to faithfully provide a “reasonable expectation” of repository performance, as specified by the EPA.
Radioelement transport in the Bangombé nuclear reactor zone (Gabon) – Evidence from U and Sm isotopes
Authors: R. Bros , G. Kamei , T. Ohnuki 
Published: April 2011

ABSTRACTAs a natural analogue study of relevance to the safety margin of radioactive waste repository conditions, mineralogical and isotopic studies were carried out to assess the effects of the alteration of the Bangombé natural nuclear reaction zone. Mobilization and retention of reactor products were identified around the reactor. The high temperature alteration associated with the heat released during nuclear reactions lead to the partial dissolution of uraninite and the sorption of released U mostly by Al-chlorite. This was followed by the precipitation of secondary U-phases such as Zr-bearing uraninite and U-Ti oxides. The recent (<1 Ma) low temperature alteration lead to further dissolution of reactor core uraninite and mobilization of U and fissiogenic REE. Migrations took place laterally through hydraulically conductive fractures within sandstones and vertically through compacted shales, likely by diffusion-type process. Adsorption onto clays and Fe-oxides is the dominant mechanism of retention as inferred by the results of selective extraction experiments. The amounts released appear to be low compared with the quantities initially produced in the core and the transfers may have been limited within several meters around the reactor.
Synthesis of Cobalt Nanoparticles, Nanorods and Nanowires assisted by Oleic Acid and Oleylamine based Mixtures.
Authors: Dumestre F. , Amiens C. , Chaudret B. , Fromen M. C. , Casanove M. J. , Renaud P. , Zurcher P. 
Published: April 2011

ABSTRACTIn this paper we report on the synthesis in solution of cobalt nanoparticles, nanorods and nanowires achieved through the decomposition of an organometallic precursor Co(η3-C8H13)(η4-C8H12) and stabilized by carboxylic acid / amine based mixtures. Through decomposition of the precursor in the presence of a 1/1 mixture of oleylamine / oleic acid during 3 hours, the formation of 3 nm spherical nanoparticles is observed while hcp-cobalt nanorods are obtained if the reaction is pursued for 48 hours. Increasing the amount of oleic acid to 2 equivalents with respect to the amine results in the formation of hcp-cobalt nanowires, micrometers in length and 6 nm mean diameter‥ By using amines with various chain lengths we have observed a modification of the aspect ratio of the cobalt nanorods1. For example, the decomposition of Co(η3-C8H13)(η4-C8H12) in the presence of octadecyl-, hexadecyl-, dodecyl- and octylamine in association with oleic acid allows to selectively produce nanorods of varying aspect ratio.Physical characterization using TEM and HRTEM, shows that the nanoparticles, nanorods and nanowires are all hcp single crystals. The magnetic properties reveal a saturation magnetization similar to that of bulk and a ferromagnetic behavior at room temperature for the nanorods and nanowires while the 3 nm nanoparticles remain super-paramagnetic.
Production Of CoPt Alloy Grains Within Protein Templates
Authors: Warne Barnaby , Mayes Eric L. 
Published: April 2011

ABSTRACTThe spherical protein ferritin can be used as a generic reaction vessel for the production of a variety of materials, such as iron and manganese oxides. Here, its use for the aqueous production of nanoparticles of equiatomically alloyed CoPt is demonstrated. These have been considered for ultrahigh density magnetic recording as well as permanent magnetic materials. This monodisperse protein strictly regulates the maximum diameter of nanocrystals synthesized within its 8 nm diameter cavity. As a consequence of its external uniformity, it decouples the formation of highly regular self-patterned films from any size distribution associated with the synthesized material. Further, its 2 nm-thick protein coating discourages sintering of particles at temperatures required for the transformation to theL10phase required for magnetic recording applications.
Capacitance-Voltage Characterization of Pulsed Plasma Polymerized Allylamine Dielectrics
Authors: Xu Yifan , Berger Paul , Cho Jai , Timmons Richard B. 
Published: April 2011

ABSTRACTPolyallylamine films, deposited on Si wafers by radio frequency (RF) pulsed plasma polymerization (PPP), were employed as insulating layers of metal-insulator-semiconductor (MIS) capacitors. The insulating polymer films were deposited at substrate temperatures of 25°C and 100°C. Multiple frequency capacitance-voltage (C-V) measurements indicated that an in-situ heat treatment during film deposition increased the insulator dielectric constant. The dielectric constant, calculated from the C-V data, rose from 3.03 for samples with no heat treatment to 3.55 for samples with an in-situ heat treatment. For both sample sets, the I-V data demonstrate a low leakage current value (<20fA) up to 100V with an area of 0.0307 mm2, resulting in a current density of <0.65 pA/mm2. Hysteresis in the C-V curves with differing sweep directions was more pronounced for in-situ heat-treated samples indicative of positive mobile ions.
Hyper-Rayleigh Scattering and Fluorescence of CdS-ZnS Nanoparticle Composites
Authors: Zhang Yu , Wang Xin , Ma Ming , Fu Degang , Zhang Haiqian , Gu Ning , Liu Juzheng , Lu Zuhong , Ma Yi , Xu Ling , Xu Jun , Chen Kunji 
Published: April 2011

ABSTRACTHyper-Rayleigh scattering (HRS) or incoherent second-order light scattering technique has been used to investigate the second-order optical nonlinearities of nanoparticles and seems sensitive to nanoparticle aggregation. In the present work, CdS and ZnS nanoparticle colloids are prepared by the method of colloidal chemistry. From absorption spectra their average diameters are determined to be 5.0 nm for CdS and 2.5 nm for ZnS. Composite CdS-ZnS colloids are obtained by mixing the two colloids at different concentration ratio. The formation of the composites is confirmed by fluorescence measurement. The reduction of emission intensity of the ZnS colloid at 428 nm is observed with increasing CdS concentration, due to fluorescence quenching of the ZnS colloid after forming CdS-ZnS composites. The apparent combining constant of the two nanoparticles is determined to be 8.1×104 mol−1.L by fitting the relative fluorescence intensity of F0/F vs. the added CdS concentration. Upon 1064 nm laser pulse excitation, HRS signal is determined at frequency-doubling wavelength (532 nm) using photomultiplier tube (PMT). HRS experiments show that the composite CdS-ZnS colloids exhibit stronger HRS signal than both CdS and ZnS colloids, and a maximum of HRS signal appears at concentration ratio of [CdS]/[ZnS]=1. This is attributed to that the composite CdS-ZnS nanoparticles have lower symmetry which contributes substantially to the second-order optical nonlinearity of nanoparticles in the electric dipole approximation.
Occurrence of ‘Accidental’ inn Quantum Dots in Indium Gallium Nitride/Gallium Nitride Heterostructures
Authors: O'Donnell K. P. , Martin R. W. , White M. E. , Pereira S. , Mosselmans J. F. W. , Tobin M. J. , Grandjean N. , Damilano B. 
Published: April 2011

ABSTRACTNakamura and co-workers were first to report the observation of spontaneously formed In-rich clusters in InGaN quantum wells (QW), using transmission electron microscopy (TEM) [1,2]. Some of the present authors have argued that the exceptional optical efficiency of nitride devices is due to the presence of nearly pure InN QD which form accidentally during crystal growth [3]. Pure InN QD with very small radius would emit light in the required spectral region, under the opposing effects of intrinsic electric fields and quantum confinement [4]. We have recently used extended X-ray absorption fine stucture to examine nanostructure [5]of molecular beam epitaxial (MBE) quantum boxes (QB), and photoluminescence excitation spectroscopy to examine their optical properties [6]. As revealed by AFM, QB are densely packed mesoscopic structures, 10–40 nm wide and 2–3 nm high. Our analysis of the QB EXAFS shows that the filling factor is of order 1%: each QB therefore contains a single QD. The optical evidence suggests that InN dots may be cubic. In contrast, TEM shows that QD in thick epilayers are sparsely distributed [7]. We re-examine recent TEM data on QW in the light of these results.
1.6 μm Emission from InAs Quantum Dots grown on a GaAs Substrate using an AlGaAsSb Metamorphic Buffer
Authors: Balakrishnan G. , Birudavolu S. , Dawson L. R. , Huffaker D. L. , Xu Huifang , Jiang Yingbing 
Published: April 2011

ABSTRACTWe report 1.6 μm emission from InAs QDs (QDs) grown on a GaAs substrate. The ensemble is grown on a graded digital alloy (DA), which increases the matrix lattice constant from 5.65 Å to 5.77 Å. The reduced lattice mismatch between the InAs and matrix material produces larger QDs and thereby allows longer wavelength emission compared to standard growth techniques. The resulting QD density ranges from 2×1010 to 8×1010/cm2 with QD dimensions of 5nm x 30nm measured using atomic force microscopy (AFM). According to x-ray diffraction (XRD) data and transmission electron microscopy (TEM), the metamorphic buffer is unstrained with low defect density.
Self Assembled PbSe Quantum Dots with Almost Equal Sizes Grown by MBE on PbTe/Si(111)
Authors: Alchalabi Karim , Zimin Dmitri , Zogg Hans 
Published: April 2011

ABSTRACTWe report on PbSe QDs grown on a few μm thick PbTe(111) layers on Si(111). The QDs form as pyramids with three (100) side faces and (111) base. Their sizes are almost equal, the standard deviation of their heights can be as low as 2–3%. This seems to be the narrowest distribution ever observed for self assembled QDs. Similar QDs of PbSe have first been described by Pinczolits et al. (Appl. Phys. Lett. 73, 250, 1998). These authors used cleaved BaF2 as a substrate, they observed two types of dots with somewhat wider size distributions. The results are compared and explained on the basis of nucleation and growth theories.
Spectroscopic Ellipsometry Studies of Nanocrystalline Silicon in Thin-Film Silicon Dioxide
Authors: Jellison Gerald E. , Jaiswal Supriya , Rouleau Christopher M. , Simpson John T. , White Clark W. , Owen C. 
Published: April 2011

ABSTRACTNanocrystalline silicon (n-Si) is formed in a silicon dioxide thin-film matrix by ion implantation followed by thermal annealing in forming gas at 1100 °C for 1 hour. The ion implantation is performed using multiple implants with different implantation energies and doses to create a quasi-flat concentration of silicon atoms throughout the silicon dioxide film. These samples are then analyzed using spectroscopic ellipsometry to characterize their linear optical properties. Implantations with small doses (5 × 1020 Si atoms/cm3) increase the refractive index by a small amount (δn∼0.006 at 600nm), while implantations with moderate dose (5 × 1021 Si atoms/cm3) have a larger increase in refractive index and exhibit optical absorption above ∼1.9 eV (650 nm).
Control of Silicon Quantum Dots nucleation and growth by CVD
Authors: Mazen F. , Baron T. , Hartmann J. M. , Semeria M. N. , Brémond G. 
Published: April 2011

ABSTRACTTo be successfully integrated in nano-electronics devices, silicon quantum dots (Si-QDs) density, density uniformity, size and size dispersion must be controlled with a great precision. Nanometric size Si-QDs can be deposited on insulators by SiH4 CVD. Their formation includes two steps : nucleation and growth. We study the experimental parameters which influence each step in order to improve the control of the Si-QDs morphology.We show that the nucleation step is governed by the reactivity of the substrate with the Si precursors. On SiO2, OH groups are identified as nucleation sites. By controlling the OH density on the SiO2 surface, we can monitor the Si-QDs density on more than one decade for the same process conditions. Moreover, Si-QDs density as high as 1.5 1012 /cm2 can be obtained. On the contrary, the growth step depends on process conditions. By modifying the gas phase composition, i.e by using SiH2Cl2 as Si precursor, we can grow the nuclei already formed during the nucleation step without formation of new Si-QDs. We discuss the advantages of this process to improve the control of the Si-QDs size and limit the size dispersion.
Anomalous X-Ray Scattering On Self-Assembled Islands: Direct Evaluation Of Composition Profile, Strain Relaxation, And Elastic Energy
Authors: Malachias A. , Magalhães-Paniago R. , Medeiros-Ribeiro G. , Kycia S. , Kamins T.I. , Stan R. 
Published: April 2011

ABSTRACTThe growth of Ge on Si(001) produces a wealth of morphologies of nanocrystals. After the deposition of a two-dimensional Ge film 3.5 monolayers thick, islands are formed, and several shape transitions can be observed depending on the growth temperature, rate and deposited thickness. In this work we combine atomic force microscopy and two different types of measurements of anomalous x-ray scattering to determine this elastic energy both in pyramid and dome shaped islands. By comparing pyramids and domes data, we have observed both an increase of lattice parameter and enhancement of interdiffusion for the domes. These results show that there is a drastic decrease of the elastic energy stored per atom upon this particular shape transition.
Sol-Gel derived Bi4-xNdxTi3O12 Thin Films and Their Characterization
Authors: Melgarejo R.E. , Tomar M.S. , Hidalgo A. , Katiyar R.S. 
Published: April 2011

ABSTRACTNd substituted bismuth titanate Bi4-xNdxTi3O12 were synthesized by sol-gel process and thin films were deposited on Pt substrate (Pt/TiO2/SiO2/Si) by spin coating. Thin films, characterized by X-ray diffraction and Raman spectroscopy, shows complete solid solution up to the composition x < 1. Initial results indicate that the ferroelectric polarization increases with increasing Nd content in the film with 2Pr = 50μC/cm2 for x = 0.46, which may have application in non-volatile ferroelectric memory devices.
The Effect of Hydrogen Incorporation on the Performance of Nanocrystalline Silicon Thin Film Transistors Fabricated by Microwave ECR Plasma CVD
Authors: Teng Lihong , Anderson Wayne A. 
Published: April 2011

ABSTRACTNanocrystalline silicon (nc-Si:H) TFT's with the active layers deposited by microwave ECR-CVD were fabricated and characterized using hydrogen dilution as a variable during the Si film deposition. The bottom-gated TFT's were fabricated on SiO2, glass and polyimide substrates at a temperature of 200–400°C with the introduction of 4–12 mTorr H2. The correlation between the H2 dilution and the TFT characteristics was studied and the experimental results were correlated with some theoretical considerations. The TFT on a glass substrate deposited at 400°C with 10 mTorr H2 showed a field effect mobility of 13.3 cm2/V-s and an ON/OFF current ratio of 4.9×106 with the OFF-state leakage current of 3.7×10−11 A. We found that, for the same Si film deposition conditions, the TFT's fabricated on polyimide foil have comparable characteristics to the TFT's on glass substrates.
Nano-Scale Morphology and Electron Spectrum of Defect States in Low-k SiOCH Films
Authors: Ligatchev V. , Wong Rusli T.K.S. , Liu B. , Ostrikov K. 
Published: April 2011

ABSTRACTResults of experimental investigations on the relationship between nanoscale morphology of carbon doped hydrogenated silicon-oxide (SiOCH) low-k films and their electron spectrum of defect states are presented. The SiOCH films have been deposited using trimethylsilane (3MS) - oxygen mixture in a 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) system at variable RF power densities (from 1.3 to 2.6 W/cm2) and gas pressures of 3, 4, and 5 Torr. The atomic structure of the SiOCH films is a mixture of amorphous-nanocrystalline SiO2-like and SiC-like phases. Results of the FTIR spectroscopy and atomic force microscopy suggest that the volume fraction of the SiC-like phase increases from ∼0.2 to 0.4 with RF power. The average size of the nanoscale surface morphology elements of the SiO2-like matrix can be controlled by the RF power density and source gas flow rates.Electron density of the defect states N(E) of the SiOCH films has been investigated with the DLTS technique in the energy range up to 0.6 eV from the bottom of the conduction band. Distinct N(E) peaks at 0.25 - 0.35 eV and 0.42 - 0.52 eV below the conduction band bottom have been observed. The first N(E) peak is identified as originated from E1-like centers in the SiC-like phase. The volume density of the defects can vary from 1011 - 1017 cm-3 depending on specific conditions of the PECVD process.
The effect of chemical treatment on porous silicon: the role of alcohol
Authors: Ohmukai Masato , Honda Mei , Kodama Yumiko , Tsunekuni Hiroshi , Tsutsumi Yasuo 
Published: April 2011

ABSTRACTWe investigated the effect of the chemical etching on light-emitting porous silicon. It is well known that the treatment with the mixture of HF acid and ethanol noticeably enhances photoluminescent efficiency but the mechanism is not clarified yet. We found that ethanol plays a key role to oxidize silicon hydride species that dissolves with the aid of HF acid. In addition, the chemical treatment with methanol or propanol instead of ethanol gave the same result.
Effects of Amorphous Carbon Films on the Performance of Porous Silicon Electroluminescence
Authors: Gelloz Bernard , Koshida Nobuyoshi 
Published: April 2011

ABSTRACTEfficient electroluminescence (EL) is obtained at low operating voltages (<3 V) from n+-type silicon- electrochemically oxidized thin nanocrystalline porous silicon (PS)-amorphous carbon-Indium tin oxide (ITO) junctions. The effects of a few nanometer thick amorphous carbon film between PS and ITO on the EL characteristics have been investigated. The carbon film enhances the stability. The EL efficiency is improved due to a reduction of current density and an increase in EL intensity. In addition, the reproducibility from device to device is very much improved by the carbon film. The enhancement in stability should originate from the capping of PS by the carbon film and the high chemical stability of carbon and Si-C bonds, which should prevent PS oxidation. The carbon film acts as an efficient buffer layer between PS and ITO, resulting in enhanced mechanical, electrical and chemical stability of the top contact and providing high reproducibility. The thin carbon film has only positive effects on all the EL characteristics. This is a very important step towards application.
The Pile-Ups Of Aluminum And Boron In The Sige(C)
Authors: Li Hong-Jyh , Onsongo David , Kirichenko Taras A. , Kohliand Puneet , Banerjee Sanjay K. 
Published: April 2011

ABSTRACTDopants diffusion, activation and pile-up due to rapid thermal annealing of implanted Al and B in a thin (∼200Å) Si cap layer on top of Si1-x-yGexCy layer were studied. Experimental results show that both the lattice strain and differential diffusion flux can cause atomic pile-up at the interface and the evidences of those effects were shown independently to each other in this paper. In addition, the pile-up can be extended from the interface to the surface by incorporating C in the underlying layer where B diffusion is much less than in the cap Si. Material analysis shows that both B atomic and activated concentrations in the Si cap layer are increased by 50 %, which suggests that the dopant activation can be increased and junction depth can be decreased at the same time using the inserted Si1-x-yGexCy diffusion blocking layer.