bluuebunny/crossref_metadata_2025 huggingface dataset:
Building Stakeholder Confidence by Reducing the Gulf between Experimental Data and Model Predictions in Assessments of Repository Performance
Authors: Hart Kaye P.
Published: April 2011

Confidence in the ability of repository systems to isolate high level wastes from the environment can be strengthened by placing greater reliance on robust designs for the repository system, and by using multiple lines of evidence to demonstrate that parameters, models and predictions developed for the repository are relevant. A particularly useful approach is to demonstrate that models and predictions incorporate processes that have been shown to be important in existing natural systems.
Measures of Geologic Isolation
Authors: Murphy William M.
Published: April 2011

Isolation in a geologic setting has been the generally favored solution to the high-level radioactive waste (HLW) problem since a scientific basis for nuclear waste management began to be formulated over half a century ago. Although general features of suitable settings have been enumerated, quantitative measures of the safety of geologic isolation of HLW are challenging to devise and to implement. Some regulatory measures of isolation for the proposed repository at Yucca Mountain, Nevada, have be devised and revised involving considerations of global releases, groundwater travel time, and time and space scales for isolation. In current Yucca Mountain specific regulations, the measure of long-term safety hinges on probabilistic estimates of radiation doses to the average member of a maximally exposed group of people living about 18 km down the groundwater flow gradient within 10,000 years after permanent closure of the repository. From another perspective, hydrogeochemical studies provide quantitative measures of system openness and the ability of geologic systems to isolate HLW. Hydrogeochemical data that bear on geologic isolation of HLW at Yucca Mountain include precipitation of radionuclides in stable mineralogical products of spent fuel alteration, ages of natural secondary mineralization in the mountain, uranium decay-series isotopic data for system openness, bomb-pulse isotope occurrences, and ambient carbon-14 distributions.
Diffuse reflectance spectroscopy of Pu ions in zirconolite and perovskite
Authors: Vance E. R. , Finnie K. S. , Zhang Y. , Begg B. D.
Published: April 2011

Diffuse reflectance spectroscopy measurements at ambient temperatures have been made over the near infrared-visible range (5000-25000 cm−1) on polycrystalline ceramic zirconolite (CaZrTi2O7) and perovskite (CaTiO3) samples doped with Pu4+. The Pu concentrations were varied between 0.001 and 0.1 formula units. The Pu ions gave rise to a number of unresolved intraconfigurational f-f electronic absorption bands of a few hundred cm−1 bandwidth. Pu ions were targeted to substitute in the Ca sites as either trivalent or tetravalent species and as tetravalent species in the Zr site of zirconolite by the appropriate choice of charge compensation and firing atmosphere. There was approximate agreement of the Kubelka-Munk absorption intensities with Beer's Law for the different Pu4+ substitution schemes, apart from some “new” bands, attributed to impurities, observed in the most dilute zirconolite sample. No clear spectral differences were evident when Pu4+ was targeted to Ca or Zr sites in zirconolite. Samples prepared in reducing atmospheres with a view to producing Pu3+ were strongly absorbing, leading to suppression of Pu transitions.
Zirconolite-Based Ceramic Formulations for Immobilization of Zr-REE-Actinide Fraction of HLW
Authors: Ochkin A.V. , Stefanovsky S.V. , Ptashkin A.G. , Mikhailenko N.S. , Kirjanova O.I.
Published: April 2011

Two ceramics for immobilization of a Zr-REE-actinide fraction of high level waste (HLW) based on zirconolite or/and pyrochlore structures with minor brannerite/lucasite, and fluorite-structured dioxide-based solid solution, were synthesized and characterized. The samples were produced by melting of oxide mixtures at 1500 °C followed by controlled cooling for crystallization. Phase compositions of the samples obtained and waste elements partitioning among co-existing phases were investigated in detail using powder X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy. Cerium enters cerianite-based solid solution, lucasite (if present), and to a lesser extent, pyrochlore and zirconolite. Europium and gadolinium enter predominantly zirconolite and pyrochlore. The highest uranium concentrations were found in a uraninite-based cubic solid solution or pyrochlore and zirconolite.
Investigation of Pu Incorporation into Zircon Single Crystal
Authors: Hanchar John M. , Burakov Boris E. , Zamoryanskaya Maria V. , Garbuzov Vladimir M. , Kitsay Alexander A. , Zirlin Vladimir A.
Published: April 2011

In order to obtain Pu-doped zircon, (Zr,Pu)SiO4, with a maximum Pu content in the form of solid solution, zircon single crystals have been grown using the flux method from starting materials overloaded with Pu. The crystals obtained ranged from 0.2-0.5 to 3.5-4.5 mm in size, are transparent, and characterized by deep pink-brown color. No inclusions of separate Pu phases were observed in the crystals. The distribution of Pu in crystals is zoned and the Pu content varying from approximately 5 to 14 wt.% el. The zircon unit cell parameters calculated from XRD data of bulk powdered sample were: a=6.620(1); c=5.989(2). The results obtained allow us to conclude that the capacity of the zircon structure to incorporate Pu exceeds 10 wt.% el.; however, additional research is required to study the extent of solid solution, (Zr,Pu)SiO4, at higher Pu contents.
REE and TRU Incorporation into Monazite Structure Ceramics
Authors: Rovnyi S. I. , Medvedev G. M. , Aloy A. S. , Koltsova T. I. , Samoylov S. E.
Published: April 2011

One of the high levels of actinide, and in particular Cm, waste streams at the Russian radiochemical Production Association (PA) Mayak was generated during spent fuel reprocessing. Using oxalate precipitation, the rare earth elements (REE) and transuranic elements (TRU) settled out in the form of oxalate residues. Due to in high REE contents in this residue, the mineral-like matrix based on (REE)PO4 solid solution, with monlclinic monazite structure have been proposed to use as a suitable ceramics form for final actinide immobilization. For this purpose the synthetic REE oxalates were first transformed into REE orthophosphates in a thin-film evaporator (TFE). Then the (REE)PO4 powder was compacted both by either hot uniaxial pressing (HUP) or cold uniaxial pressing followed by sintering (CUP). This ceramic with the monazite structure has a high density and exhibits chemical durability by leaching.
Effect of Alpha Decay on Nuclear Borosilicate Glass Properties
Authors: Peuget Sylvain , Jégou Christophe , Broudic Véronique , Roudil Danièle , Deschanels Xavier , Bart Jean-Michel
Published: April 2011

The properties of actinide glasses are studied in the context of high-level waste management programs. Reprocessing high burnup fuels in particular will increase the minor actinide content in the glass package, resulting in higher cumulative alpha decay doses in the glass, and raising the question of the glass matrix behavior and especially its containment properties. The effect of alpha self-irradiation on the glass behavior is evaluated by doping the glass with a short-lived actinide (244Cm) to reach in several years the alpha dose received by the future glass packages over several thousand years. “R7T7” borosilicate glasses were doped with 3 different curium contents (0.04 wt%, 0.4 wt% and 1.2 wt% 244CmO2). The glass homogeneity was characterized by SEM and XRD. Chemical analysis after dissolution of the glass confirmed the chemical composition. The curium content and its distribution in the glass specimens were checked by calorimetry measurements and gamma spectrometry on 243Cm and 245Cm isotopes. The density and mechanical properties of the curium-doped glasses were characterized up to 2 × 1018 α/g, revealing only a slight evolution of the macroscopic behavior of R7T7 glass in this range. The leaching behavior of curium-doped glass was also studied by Soxhlet tests. The results do not show any significant evolution of the initial alteration rate with the alpha dose.
Corrosion mechanisms of low level vitrified radioactive waste in a loamy soil
Authors: Ojovan M.I. , Lee W.E. , Barinov A.S. , Ojovan N.V. , Startceva I.V. , Bacon D.H. , Mcgrail B.P. , Vienna J.D.
Published: April 2011

Field experiments have run for over 14 years to evaluate the behaviour of the same high-sodium content radioactive waste borosilicate glass buried in a loamy soil (glass K-26) and in an open testing area (glass Bs-10). Processing of field data for glass Bs-10 tested in an open area has resulted in a dissolution rate r = 0.42 µm/y and caesium diffusion coefficient D ≍ 1.8 10−20 m2/s at testing temperatures up to 19 oC. Both ion-exchange and hydrolysis control the corrosion of this glass. Processing of field data for K-26 glass revealed an insignificant role of glass dissolution. The caesium diffusion coefficient was estimated as D ≍ (3.4-5.1) 10−21 m2/s. Due to the relatively low storage temperatures (4.5 oC) used the leaching behaviour of glass K-26 is believed to be controlled by ion exchange processes. This mechanism is likely to remain dominant until the decay of 137Cs in the glass is below exemption levels.
Characterization of Chromium(III) Hydroxide Solids and Their Oxidation by Hydrogen Peroxide
Authors: Zhang Zhicheng , Rao Linfeng , Rai Dhanpat , Clark Sue B.
Published: April 2011

Chromium is of great concern in the vitrification of high-level nuclear waste sludges because it forms separate crystallites in the molten glass. Inadequate removal of chromium from sludges could result in the production of an unacceptably large volume of HLW glass. Alkaline oxidative leaching is considered one of the pretreatment strategies to remove chromium before the vitrification.

In this study, Cr(III) hydroxide solids were prepared under different conditions and characterized by EXAFS and IR. The rate of oxidation of the solids by hydrogen peroxide in alkaline solutions was studied by UV absorption spectroscopy. EXAFS and IR experiments indicate that the degree of oligomerization in the Cr(III) hydroxide solids increases with the increase in the concentration of NaOH in solution, the aging temperature and the aging time. The rate of oxidation of the solids follows the same order previously observed for Cr(III) oligomers in solution, i.e., species with higher degree of oligomerization are oxidized more slowly.
Formation Rate and Compositions of the Actinide Hosts with Garnet Structure
Authors: Ioudintseva Tatiana S. , Chae Soo-Chun
Published: April 2011

Garnet phases have been considered as a durable crystalline waste form for hosting actinide. The garnet-structure phases with stoichiometries of Ca2,5Ce0,5Zr2Fe3O12, Ca2CeZrFeFe3O12, and Ca1,5GdCe0,5ZrFeFe3O12 were synthesized through cold pressing and sintering in air and oxygen to determine the optimum parameters for the formation of actinide waste forms. Cerium (Ce) was used as an imitator of plutonium due to its similarity in oxidation state and ionic radii. Gadolinium (Gd) plays a major role as an absorber of neutrons that prevents nuclear chain reaction. It also serves as imitators of the trivalent actinides. Ce-garnet or (Ce,Gd)-garnet is chemically analogous to the garnets with plutonium and/or trivalent actinides. The results of XRD and SEM-EDS examination of the products of experiments reveal that equilibrium state was reached at the temperatures of 1300 °C and 1200 °C for 1 and 5 hours heating, respectively.
Analytical STEM of Borosilicate Glasses Containing Molybdates.
Authors: Short Rick J. , Möbus Günter , Yang Guang , Hand Russell J. , Hyatt Neil , Lee William E.
Published: April 2011

Borosilicate nuclear waste glasses with various amounts of simulated waste elements have been examined by analytical TEM. This preliminary Scanning Transmission Electron Microscopy (STEM) study evaluates the capability of EELS for mapping coordination parameters of the base glass structure, to apply EDX-mapping and HAADF Z-contrast mapping for the characterisation and shape-mapping of common precipitates in nuclear glasses, such as molybdates, and to study irradiation effects.
Solubility of Niobium(V) under Cementitious Conditions: Importance of Ca-niobate
Authors: Talerico Caterina , Ochs Michael , Giffaut Eric
Published: April 2011

The solubility of niobium was investigated for Ca and pH conditions relevant for cementequilibrated solutions. For the pH range considered (9.5-13.2), the dissolved Nb concentration decreases with increasing pH. Overall, experiments lead to Nb concentrations between 2·10-5 M and 2·10-9 M. For all pH values, the dissolved Nb concentration also decreases systematically with increasing Ca concentration. X-ray diffraction measurements of selected experiments confirmed the presence of a solid Ca-Nb-oxide phase, with CaNb4O11·8H2O (hochelagaite) being the most likely composition. On the basis of these findings an empirical regression model for the prediction of Nb solubility data as a function of pH and Ca concentration was derived. This empirical relation is consistent with the presence of a solubility limiting Ca-Nb solid phase and permits to predict aqueous Nb solubility values in cementitious environments over a relatively wide range of conditions. Predicted values are in good agreement with independent experimental results.
Electrochemical Evaluation and Surface Characterization of Josephinite as a Natural Analog for Container Materials
Authors: Pan Yi-Ming , Cragnolino Gustavo A.
Published: April 2011

A sample of josephinite, a rock containing predominantly a Ni-Fe metallic phase, was evaluated as a natural metal analog to increase confidence in the assessment of waste package performance for the potential high-level radioactive waste repository at Yucca Mountain, Nevada. The josephinite sample was characterized electrochemically in simulated groundwater environments using cyclic potentiodynamic polarization and potentiostatic tests. The passive surface layers formed potentiostatically were examined by X-ray photoelectron spectroscopy. These results were compared to those obtained with a synthetic Ni3Fe alloy with a chemical composition similar to that of josephinite. Electrochemical studies showed that josephinite exhibited passivity at a slightly higher pH than did the cast Ni3Fe alloy and was found to be slightly more susceptible to pitting corrosion. The passive films formed on the josephinite and the cast Ni3Fe alloy have a duplex structure consisting of an Fe-rich hydroxide outer layer and a Ni-rich oxide inner layer. Results obtained from this study provide an appropriate characterization of the environmental conditions leading to the passivity and localized corrosion of josephinite. Extended persistence of a stable passive film, however, is essential for the long-term stability of the josephinite sample. The relationship between the passive behavior and the formation of alteration layers needs to be established for assessing the survivability of josephinite.
Influence of Defect Interactions on Diffusion Processes in UO2+x: a Key Issue for Understanding the Behaviour of Spent Nuclear Fuel.
Authors: Petot-Ervas Georgette , Baldinozzi Gianguido , Ruello Pascal , Desgranges Lionel , Chirlesan Georgeta , Petot Claude
Published: April 2011

The transformation of UO2 into U3O8 is of technological and academical interest because of the severe consequences on the spent nuclear fuel management. The structural mechanism responsible for the isothermal transformation of UO2 into U3O8 seems still unclear. Several phases (UO2+x, U4O9, β-U3O7, α-U3O7, U3O8 were reported but their true structures, phase boundaries between their existence domains and matter transport processes are still a matter of debate. Gathering accurate information on the behaviour of uranium oxide is a key issue for understanding the behaviour of spent nuclear fuel. The chemical diffusion coefficient ( ~ D) of UO2+x was determined by electrical conductivity experiments. Measurements were performed in transient state for departure from stoichiometry in the range 0<x<0.17 (10-11<P(O2)<10-8 atm.)and for 973<T<1673 K. We have found that ~ D is a decreasing function of the departure from stoichiometry x. This behaviour was attributed to the presence of singly charged (2:2:2) Willis defects as suggested by equilibrium conductivity measurements. The decrease of Dchim can be explained by transport processes occurring via a dynamic exchange between isolated mobile defects and complex defects frozen in clusters or domains. At higher P(O2), near U4O9, the time to reach an equilibrium electrical conductivity value becomes increasingly long. This suggests the presence either of large defect aggregates or of complex defects arranged into domains. Furthermore, the analysis of the transport processes in non equilibrium conditions has allowed us to show that the results of ~ D are consistent with those of the oxygen diffusion coefficient within the P(O2) and temperature range of stability of the [2:2:2] clusters.
Coprecipitation Experiments Using Simulated Spent Fuel Solutions in the Presence of Metallic Iron in Synthetic Bentonitic-Granitic Water Under Oxidising Conditions
Authors: Quiñones Javier , Huebra Ángel González de la , Esparza Aurora Martínez
Published: April 2011

This paper presents the results obtained from coprecipitation experiments of uranyl solutions in the presence of metallic iron and/or its alteration phases in synthetic bentonitic-granitic composition water. Experiments were done under oxidising conditions at room temperature. The pH range covered was 7.4 – 8.8. Changes in the uranium concentrations and the characterisation of the secondary phases formed in the experiments were done using XRD and SEM-EDS and are presented herein.

Final uranium concentration values were in the range of 2·10−5 – 5·10−4 mol (kg of H2O)−1. In all cases, results from these experiments did not show evidence of a clear effect due to the presence of iron (metallic or previously corroded) on the uranium concentration. These data were similar to those obtained by coprecipitation in similar conditions but in absence of iron material. Boltwoodite was observed [K2(UO2)2(SiO3)2(OH)2·3H2O] in iron surface materials and characterized in all experiments. Based on the experimental data obtained (uranium concentration in solution and bulk solid phase characterisation) we propose the following surface-mediated reaction:

2 K+ + 2 H4SiO4 + 2 UO2+2 + 3 H2O ⇔ K2(UO2)2(SiO3)2(OH)2·3H2O + 6 H+
The Effect of Alpha-Radiolysis on UO2 Dissolution Determined from Batch Experiments with 238Pu-Doped UO2
Authors: Stroes-Gascoyne Simcha , Betteridge James S.
Published: April 2011

Dissolution experiments were performed with 238Pu-doped UO2 containing doping levels of ∼1–100 Ci/kg UO2, in 0.1M perchlorate with or without 0.1M carbonate, at pH 9.5, to investigate the effects of α dose-rate on UO2 dissolution rates and on Geff, the fraction of radiolytically produced H2O2 supporting dissolution. Dissolution rates increased by only about 10 times for a ∼100-fold increase in doping level in both solutions, but increased between 10 and 100 times in 0.1M carbonate, compared to dissolution rates in 0.1M perchlorate. Geff values increased with decreasing doping level, suggesting that the dissolution reaction is limited by the reaction rate between UO2 and H2O2 at high dose rates, but becomes limited by the rate of production of H2O2 at lower dose rates.
Optical properties of transition metal (Mn, Fe and V) doped Zinc Oxide ceramics and thin films
Authors: Awasthi Neha , Bhattacharya P. , Katiyar R.S.
Published: April 2011

Transition metal doped (Mn, Fe and V) ZnO ceramics and their thin films were prepared by pulsed laser deposition on glass substrates. The ceramic targets did not show any additional phase formation from XRD measurement, except for high Fe concentrations. Optical absorption showed sub-band gap absorption for Mn doping. The band gap was shifted by 0.06 eV for V doped ZnO as concentration was increased to 10%. Micro Raman spectra showed some defect induced modes for all the transition metals doped ZnO ceramics. In V doped ZnO ceramics there was two phonon induced resonance Raman scattering with increase in dopant concentrations. Raman spectra for thin films did not show any significant additional modes for Mn and Fe. However V doped ZnO thin films showed an additional mode for concentration ≥5 %.
Optimization of Sample Holder Materials for Sensitive Magnetometry Measurements at Low Temperatures
Authors: Bossi I. , Dilley N.R. , O'Brien J. R. , Spagna S.
Published: April 2011

Magnetization measurements were performed as a function of magnetic field H and temperature T on samples of nine different materials including clear fused quartz, cartridge brass, G-10 glass-reinforced epoxy, acetal homopolymer, glass-filled acetal, phenolic, and other plastics. A small yet distinct amount of ferromagnetic or paramagnetic impurities is observed in all the materials investigated in this study except quartz. In contrast, the magnetic response of quartz is typical of a diamagnet over the temperature range 5 K to 300 K. The volume susceptibility is equal to −4.4×10−7 (cgs) over the whole temperature range.
Stability of Chemically Crosslinked Microtubules
Authors: Boal Andrew K. , Rivera Susan B. , Miller Nicholas E. , Bachand George D. , Bunker Bruce C.
Published: April 2011

Microtubules (MT) are dynamic protein-based polymers with numerous applications in materials science including the active transport of nanomaterials and as templates for biomimetic materials synthesis. Some of these applications require that the dynamic nature of the MT be suppressed, and in this report we will discuss the preparation and stability of chemically crosslinked microtubules (CLMTs). MT reaction with gluteraldehyde results in the formation of protein dimers and higher molecular weight oligimers as observed by gel electrophoresis, confirming the formation of covalent inter-protein linkages. While extensive crosslinking was found to destabilize MTs and inactivate them with regards to kinesin binding, moderate amounts of crosslinking lead to CLMTs that had functional lifetimes of at least twice that of uncrosslinked MTs. Further studies demonstrated that CLMTs exhibited a wider thermal stability window and were far more resistant to metal-ion induced depolymerization than uncrosslinked MTs.
Biomedical Nanoscience: Electrospinning Basic Concepts, Applications, and Classroom Demonstration
Authors: Pawlowski Kristin J. , Barnes Catherine P. , Boland Eugene D. , Wnek Gary E. , Bowlin Gary L.
Published: April 2011

Electrospinning is an old polymer processing technique that has recently been rediscovered. It allows for the easy creation of nano- to micro-fibers that can be collected to form a non-woven structure, which can then be used to fabricate novel structures for various applications including tissue engineering scaffolds, clothing, drug delivery vehicles, and filtration media. Current research in our laboratories is focused on the processing of synthetic and biological polymers to create materials with tailored properties and functions for tissue engineering scaffolds and various other medical applications. This technology is revolutionizing the biomaterials and nanotechnology fields and has prompted us to incorporate its history, basic concepts, and applications into diverse courses such as Biomaterials, Tissue Engineering, Polymers in Medicine, and Senior Design in Chemical and Biomedical Engineering. This Innovation of the Curriculum is timely and crucial for multiple reasons. There is a need for a systematic approach to course structure that ties historical concepts to new materials and processes and, ultimately, to practical applications. Combining this lecture organization with active learning in the forms of open discussions and hands-on experiments/demonstrations will enhance learning outcomes (including retention and critical thinking) at all levels of education. At the undergraduate and graduate levels in the courses mentioned, discussions of electrospinning can create a classroom atmosphere of creative thinking, and an actual demonstration of nanomaterial fabrication can serve as a visual aid to the students. More importantly, this curriculum innovation can be used at the high school level to demonstrate nanotechnology and its applications to medicine, which will aid in sparking the interest of future generations of tissue engineers, biomaterial scientists, nanotechnologists, and scientists and engineers in general.
MatDL.org: The Materials Digital Library and the National Science Digital Library Program
Authors: Bartolo Laura M. , Glotzer Sharon C. , Khan Javed I. , Powell Adam C. , Sadoway Donald R. , Anderson Kenneth M.
Published: April 2011

The National Science Foundation's National Science Digital Library (NSDL) Program is a premier collective portal of authoritative scientific resources supporting education and research. With funding from NSF, the Materials Digital Library (MatDL) is a collaborative project being developed by the National Institute of Standards and Technology's Materials Science and Engineering Laboratory (NIST/MSEL), the Department of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT), the Department of Chemical Engineering and the Department of Materials Science and Engineering at the University of Michigan (U-M), with Kent State University and University of Colorado at Boulder providing the materials science informatics and workflow technology backbone. As part of the NSDL program, MatDL aims to supports the interface of materials science information and its cognate disciplines, with an emphasis on soft matter. Initial content of MatDL begins with resources selected from NIST/MSEL. Students and faculty in three types of materials science and engineering (MSE) courses at MIT and U-M are taking part in a pilot to use and contribute to MatDL utilizing domain-specific authoring tools. Given the central and interdisciplinary role of materials science in science and engineering, two goals of MatDL are to: 1.) expand its founding partnership with additional participants from the MSE community; and 2.) facilitate the flow of digital materials related knowledge from laboratories where the most recent research discoveries are taking place to the classrooms where new scientists are being trained.
Implementation of Paul Revere: Tough as Nails, an Integrated Project-Based Course on Materials Science and History of Technology
Authors: Stolk Jonathan , Martello Robert , Olin Franklin W.
Published: April 2011

Olin College sophomores participate in integrated course blocks that merge technical content with business, arts, humanities, and social science topics, allowing students to work on engineering projects that have broader implications than the purely technical. In this paper, we present Paul Revere: Tough as Nails, a multidisciplinary course block that combines an introductory materials science course with a history of technology course and a large scale project. In Paul Revere, students explore connections between historical and technological materials science developments through examinations of Paul Revere's metallurgical work and analyses of the relevant social, environmental, political, and economic aspects that contribute to ancient and modern technologies. The explicit linkages among technical, non-technical, and hands-on aspects of the course improve learning of traditional topics, help drive interdisciplinary thinking, and lead to a high level of student satisfaction and motivation throughout the semester.
Curricula For A Sustainable Future: A proposal for integrating environmental concepts into our curricula
Authors: Vanasupa Linda , Splitt Frank G.
Published: April 2011

The global scientific community recognizes the critical need for industries to develop and practice manufacturing techniques that minimize harm to our environment. In the National Science Board's report Environmental Science and Engineering for the 21st Century, the National Science Foundation was urged to promote “Environmental research, education, and scientific assessment [as] one of NSF's higher priorities.” Although there are a number of independent efforts to fold environmental issues in existing undergraduate curricula, no dominant method has emerged as a means of including these concepts. One of the difficulties in adjusting our materials science and engineering (MSE) curricula is the problem of how and what to include in an already full curriculum. In this paper, we propose a path for integrating environmental and sustainability concepts within the framework of existing curricula. We will suggest learning outcomes for each year of the MSE curriculum and offer examples.
Electrochemically Fabricated Conducting Polymer Nanoframework Electrode Junctions That Function as Resistive Sensors
Authors: Tseng Hsian-Rong , Wang Jun , Alam Maksudul M.
Published: April 2011

We have demonstrated a template-free, site-specific, and scalable electrochemical method for the fabrication of individually addressable conducting polymer nanoframework electrode junctions in a parallel-oriented array. These conducting polymer nanoframeworks, which are composed of numerous intercrossing conducting polymer nanowires that have uniform diameters ranging from 40 to 150 nm, can be used for the chemical sensing of HCl and NH3 gases and organic vapors and for sensing pH values of aqueous solutions.
Effect of Thickness of Ion Beam Deposited Molybdenum Trioxide Thin Films on Gas Sensing Properties
Authors: Prasad Arun K. , Gouma Pelagia I.
Published: April 2011

This paper documents the study of thickness effects of ion beam deposited molybdenum trioxide thin films on their gas sensing properties. For processing the films, the primary plasma beam source was used to sputter material from the target, while the secondary beam was used as an ion assist source. The deposited material was annealed at 500°C for 8 hours. The microstructural characterization of the films was done using Scanning Electron Microscopy and X-ray diffraction. Sensing tests were performed in the temperature range of 350–500°C under varying and constant concentration levels of ammonia. The recorded data have been qualitatively and quantitatively analyzed and significant trends according to different parameters (thickness, sensing temperature, gas concentration) have been identified. These suggest a relation existing between processing conditions, the microstructure of the material and its response to gases at different concentration, and the optimum working temperature regime.
Sensing behavior of perovskites GdCo1−xCuxO3 prepared by solution and ultrasonic-assisted aerosol methods.
Authors: Michel Carlos R. , López Edgar R. , Chávez Arturo
Published: April 2011

Polycrystalline samples of GdCo1−xCuxO3 (x=0, 0.15, 0.3), were prepared by two different routes: solution and ultrasonic-assisted aerosol decomposition. For both procedures, aqueous solutions containing stoichiometric amounts of Gd(NO3)36H2O, Co(NO3)26H2O and Cu(NO3)22.5H2O were used. In the solution method, the aqueous solutions were heat-dried at 76°C obtaining precursor powders, these were calcined from 80 to 950°C, in air. In the aerosol method, very small droplets were produced by an ultrasonic generator, then a flow of oxygen transported the mist through a tubular furnace, previously heated at 950°C. Solvent evaporation and chemical reaction takes place at that temperature, and the resulting powder was collected by filtration. X-ray powder diffraction was used to identify the formation of target phases. Surface microstructure of powders was analyzed by SEM, and showed that solution method produced sub-micron particles with irregular shape, whereas the aerosol method yield micron-sized hollow spherical particles. In order to determine gas sensitivity vs. temperature, electrical measurements were made in air, O2 and CO2, from room temperature to 650°C. The results showed a semiconductor behavior and a moderate gas sensitivity for samples prepared by solution method. However, unreliable data were registered for samples made by the aerosol route, caused by short connectivity between particles.
Chemical Synthesis, Characterization and Gas-Sensing Properties of Thin Films in the In2O3-SnO2 System
Authors: Epifani Mauro , Díaz Raül , Taurino Antonella , Francioso Luca , Siciliano Pietro , Morante Joan R.
Published: April 2011

Thin films in the SnO2-In2O3 system, with relative concentrations of the two oxides ranging from 2% to 98% (molar percentage of the oxide), were deposited by sol-gel and solution processes. The films for the physical characterizations were deposited onto oxidized silicon substrates, while the films for the gas-sensing tests were deposited onto alumina. The starting solutions were characterized by FTIR spectroscopy, while the films on silicon, heated at various temperatures, were characterized by X-ray diffraction and SEM observations. The interaction between the two systems is particularly evident in the case of the system described by a 50% In2O3-50% SnO2 nominal composition. The crystallization on In2O3 during the film heat-treatment hinders the crystallization of SnO2, thus Sn is dispersed as an n-dopant in the In2O3 lattice, indeed showing a current signal, in the gas-sensing test, two orders of magnitude higher than the pure film. The response of the mixed-oxide based device to NO2 is better than pure In2O3. On the other hand, the response (relative resistance change) of pure SnO2 to low (from 0.1 to 1 ppm) NO2 concentrations ranges from 150 to 300, a result that can be correlated with the nanostructure of the film, which, from SEM and XRD results, seems constituted by very small grains.
Synthesis of Monolayer-Capped GaAs Nanoparticles
Authors: Luo Jin , Wang Lingyan , Han Li , Maye Mathew M. , Wang Jian Q. , Altman Eric I. , Zhong Chuan-Jian
Published: April 2011

This paper reports the preliminary results of an investigation of the synthesis of monolayer-capped GaAs nanoparticles using different surface capping molecules. Our approach focuses on the surface encapsulation using alkanethiolates. The organic shell can effectively block the aggregation during nanoparticle synthesis, providing molecular-level control of the core-shell structure. The results have demonstrated the effect of surface alkanethiolate modification on the interparticle spatial properties and particle sizes, which upon further refinement could lead to the ability in controlling the size of GaAs nanoparticles.
The Development and Evaluation of TiO2 Nanoparticle Films for Conductometric Gas Sensing on MEMS Microhotplate Platforms
Authors: Benkstein Kurt D. , Montgomery Christopher B. , Vaudin Mark D. , Semancik Steve
Published: April 2011

Over the past decade, MEMS microhotplate devices have been developed at the National Institute of Standards and Technology to support semiconductor metal oxide films for use in conductometric gas sensor arrays. In most cases, the materials have been based on compact thin films of SnO2 or TiO2 deposited by single-source precursor chemical vapor deposition. Of particular interest to our group is the enhancement of the sensitivity of the microsensors to trace gas species by inducing nanostructured porosity and large internal surface areas in the films. In this presentation, we discuss the development of nanostructured sensor materials based on porous TiO2 nanoparticle thin films. The preparation and evaluation of pure and Nb-doped TiO2 nanoparticle films are described. The films on the MEMS microhotplate substrates are evaluated as conductometric gas sensors based on the critical performance elements of sensitivity, stability, speed and selectivity. The sensor performance, and specifically the sensitivity, of the novel nanoparticle TiO2 films is compared with that of traditional compact CVD-derived films.
Floating-Gate Ion Sensitive Field-Effect Transistor for Chemical and Biological Sensing
Authors: Zhao Ben , Sai Tsunehiro , Rahman Arifur , Levon Kalle
Published: April 2011

This paper presents the use of Floating-Gate Ion Sensitive Field-Effect Transistor (FGISFET) as a real-time chemical and biological sensor. The structure of FGISFET is similar to that of an electrically erasable programmable read-only memory (EEPROM). The floating-gate of a FGISFET is connected to an exposed metallic structure, which serves as a probe for detecting ionic activities. By applying ion-sensitive chemical and biological materials to the floating gate, its threshold voltage can be modulated in the presence of selective chemical or biological targets. As a demonstration, FGISFETs have been fabricated in 1.2 μm process technology available through MOSIS [1]. Our preliminary measurements confirmed the basic design and operation of FGISFET, and using doped aniline trimer (TANI) as a sensing material, we were able to sense 70ppm of ammonium gas.
Non Volatile Memory Technologies: Floating Gate Concept Evolution
Authors: Clementi Cesare , Bez Roberto
Published: April 2011

The most relevant phenomenon of this last decade in the field of semiconductor memories has been the explosive growth of the Flash memory market, driven by cellular phones and other types of electronic portable equipments (palm top, mobile PC, mp3 audio player, digital camera and so on). Moreover, in the coming years portable systems will ask even more non volatile memories either with high density and very high writing throughput for data storage application, or with fast random access for code execution in place. The strong consolidated know-how (more than ten years of experience), the flexibility and the cost make the floating gate Flash Memory a largely utilized, well-consolidated and mature technology for most of the non-volatile memory application. Today Flash sales represent a considerable amount of the overall semiconductor market.

Nowadays two of the several cell architecture proposed up to now can be considered as industry standard: the common ground NOR Flash that due to its versatility is addressing both the code and data storage segments and the NAND Flash, optimized for the data storage market.

The exploitation of the multilevel approach at each technology node allows the increase of the memory efficiency, about doubling the density at the same chip size, widening the application range and reducing the cost per bit.

In this paper the main issues related to both NOR and NAND Flash memory technology will be summarized, with the aim of describing both the basic functionality of the memory cell and the main cell architecture today consolidated. Both cells are basically a floating-gate MOS transistor, programmed by channel hot electron (NOR) or by Fowler-Nordheim tunneling (NAND) and erased by Fowler-Nordheim tunnel. The main reliability properties, charge retention and endurance, are presented, together with some comments on the basic physical mechanisms responsible for.

A couple of innovative approaches to floating gate cell evolution, namely nanocrystal memory and 3-D cell will be described.

Finally the Flash cell scaling issues will be covered, pointing out the main challenges. The Flash cell scaling has been demonstrated to be really possible and to be able to follow the Moore's law down to the 90 nm technology generations. The technology development and the consolidated know-how are expected to sustain the scaling trend down to the 50 nm technology node and below as forecasted by the ITRS roadmap.
Characterization of MFMIS and MFIS Structures for Non-volatile Memory Applications
Authors: Rahman Mosiur , Kalkur T. S. , Sun Shunming , Gnadinger Fred P. , Dalton David , Kim Daesig , Olariu Viorel , Klingensmith David
Published: April 2011

To eliminate the interface reaction problems between ferroelectric and semiconductor in MFS (metal-ferroelectric-semiconductor) as well as ferroelectric and insulator in MFIS (metal-ferroelectric-insulator-semiconductor) structures, a gate layer sandwich of the MFMIS (metal-ferroelectric-metal-insulator-semiconductor) is proposed. This structure consists of Pt-SBT-Pt-ZrO2-SiO2-Si stacks. In the MFMIS structure the MIS capacitor is separated from the ferroelectric MFM capacitor through a metal as a floating gate. Therefore, the MIS capacitor with SiO2 and ZrO2 as an insulator with excellent interface properties can be used and MFM acts as an ideal ferroelectric capacitor. As MFMIS is a series combination of MFM and MIS capacitors, it behaves as a voltage divider. The gate voltage is divided according to the capacitance ratio of the MIS and MFM structures. Since the fabricated devices have access to the floating gate, characteristics of the MFM and MIS capacitors can be determined independently to compare the characteristics of the MFMIS structure as a single capacitor. The ferroelectric can be programmed in one direction and the field effect due to that can be analyzed. The MFMIS structures showed significant memory window due to the polarization of ferroelectric thin films but the retention time was short. The short retention time was due to the depolarization field being larger than coercive field of the ferroelectric thin film.
Characterization of Electronic Charged States of Silicon Nanocrystals as a Floating Gate in MOS Structures
Authors: Miyazaki Seiichi , Shibaguchi Taku , Ikeda Mitsuhisa
Published: April 2011

We have studied capacitance-voltage (C-V) and displacement current-voltage characteristics of MOS capacitors with Si nanocrystals embedded in the gate oxide as a floating gate in dark and under visible light illumination at room temperature to gain a better understanding of discrete charged states of the Si-dots floating gate. The Si-dots floating gate with a dot density of 2.8×1011cm-2 and an average dot size of 8nm was fabricated on ∼2.8nm-thick thermally-grown SiO2 as a tunnel oxide by the thermal decomposition of SiH4, and covered with 7.5nm-thick control oxide prepared by thermal oxidation of a-Si. C-V characteristics of Al-gate MOS capacitors on p-type and n-type Si(100) show unique hystereses due to the charging and discharging of the Si-dots floating gate with a symmetric pattern reflecting the Fermi level of the substrate, which enable us to rule out the contribution of traps with a specific energy state to the observed hystereses. For each of high-frequency C-V curves measured in dark, a single capacitance peak appears only around a flat-band voltage condition, which is attributed to the quick flat-band voltage shift caused by the collective emission of charges retaining in the Si-dots floating gate as confirmed from the corresponding displacement current peak. Under visible light illumination, another capacitance peak due to collective charge injection to the electrically neutral Si-dots floating gate becomes observable in the inversion condition governing the on-state of MOS FETs. Thus, the optimum bias conditions for dot-floating gate MOSFETs can be predicted from the capacitor characteristics measured under light illumination.
Enhanced Spontaneous Polarization of Dysprosium-substituted Lead Zirconate Titanate Thin Films by a Chemical Solution Deposition Method
Authors: Uchida Hiroshi , Nakaki Hiroshi , Okamoto Shoji , Yokoyama Shintaro , Funakubo Hiroshi , Koda Seiichiro
Published: April 2011

Influences of the B-site substitution using Dy3+ ion on the crystal structure and ferroelectric properties of lead zirconate titanate (PZT) films were investigated. Dy3+-substituted PZT films with nominal chemical compositions of Pb1.00Dyx (Zr0.40Ti0.60)1-(3x/4)O3 (x = 0 ∼ 0.06) were fabricated by a chemical solution deposition (CSD). Polycrystalline PZT films with preferential orientation of (111)PZT were obtained on (111)Pt/TiO2/SiO2/(100)Si substrates, while epitaxially-grown (111)PZT films were fabricated on (111)SrRuO3//(111)Pt//(100)YSZ//(100)Si substrate. Ratio of PZT lattice parameters (c/a), which corresponds to its crystal anisotropy, was enhanced by the Dy3+-substitution with x = 0.02. Spontaneous polarization (Ps) of Dy3+-substituted PZT film (x = 0.02) along polar [001] axis of PZT lattice was estimated from saturation polarization (Psat) value of the epitaxially-grown (111)PZT film on (111)SrRuO3//(111)Pt//(100)YSZ//(100)Si to be 84 μC/cm2 that was significantly larger than that of non-substituted PZT (= 71 μC/cm2). We concluded that the enhancement of Ps value could be achieved by the Dy3+-substitution that promoted the crystal anisotropy of PZT lattice.
Synthesis and Electrical Characterization of a MOS Memory Containing Pt Nanoparticles Deposited at a SiO2/ HfO2 Interface
Authors: Sargentis Ch. , Giannakopoulos K. , Travlos A. , Tsamakis D.
Published: April 2011

MOS memory devices containing semiconductor nanocrystals have drawn considerable attention recently, due to their advantages when compared to the conventional memories. Only little work has been done on memory devices containing metal nanoparticles.

We describe the fabrication of a novel MOS device with embedded Pt nanoparticles in the HfO2 / SiO2 interface of a MOS device. Using as control oxide, a high-k dielectric, our device has a great degree of scalability. The fabricated nanoparticles are very small (about 5 nm) and have high density. High frequency C-V measurements demonstrate that this device operates as a memory device.
Experimental Observation of Non-Volatile Charge Injection and Molecular Redox in Fullerenes C60 and C70 in an EEPROM-Type Device
Authors: Ganguly Udayan , Lee Chungho , Kan Edwin C.
Published: April 2011

Molecular interface with CMOS is an area indispensable to the enhancement of our understanding of the nano-scale world. We report the integration of fullerenes in CMOS gate stack and demonstrate a functional molecular interface by effecting molecular redox operations through non-volatile charge injection in an EEPROM-type device. The gate stack of the MOS capacitor consists of a tunneling thermal oxide. A sub-monolayer of fullerenes is deposited. Then the control oxide is deposited and finally the gate metal is patterned. Charge injection occurs at a specific potential of the fullerene molecules with respect to the conduction band of Si at the Si/SiO2 interface, independent of the concentration of the fullerene sub-monolayer. This strongly indicates molecular redox in solid state that is electrostatically controllable. Such molecular interfaces can be used to enhance the spatial sensitivity of chemical sensors like the CνMOS to be able to interface with macromolecular systems.