bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solubility of Niobium(V) under Cementitious Conditions: Importance of Ca-niobate
Authors: Talerico Caterina , Ochs Michael , Giffaut Eric 
Published: April 2011

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThis 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

AbstractDissolution 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

AbstractTransition 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

AbstractMagnetization 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

AbstractMicrotubules (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

AbstractElectrospinning 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

AbstractThe 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

AbstractOlin 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

AbstractThe 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

ABSTRACTWe 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

ABSTRACTThis 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

ABSTRACTPolycrystalline 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

ABSTRACTThin 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

ABSTRACTThis 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

ABSTRACTOver 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.