bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of the Weathering Properties of Minerals Based on the Ion-Ion Interaction Potential
Authors: Raicevic Slavica , Wright Judith V. , Vujic Jasmina , Conca James L. 
Published: April 2011

AbstractSelection of solid matrix for immobilization of nuclear waste and of geological sites for its disposal represents a complex and consuming task. Previously, we demonstrated that the ion-ion interaction potential (IIIP), representing the main term of the cohesive energy, can be used for estimation of stability of solid matrix/impurity systems. Here we demonstrated a strong correlation between the weathering properties of minerals and their IIIP. Based on these results we proposed a simple theoretical criterion which can be used for assessment of the long term stability of solid matrix for immobilization of radioactive and toxic metals. This criterion was applied in analysis of stability of autunites and some possible practical consequences of results obtained for immobilization of uranium by apatite are discussed.
Neptunium(V) Incorporation/Sorption with Uranium(VI) Alteration Products
Authors: Friese J. I. , Douglas M. , Buck E. C. , Clark S. B. , Hanson B. D. 
Published: April 2011

AbstractAn initial uranium phase that has been observed to form during the corrosion of spent nuclear fuel is the uranium oxy-hydroxide metaschoepite. It has been proposed that neptunium(V) solubility can be limited by its association with this uranium phase. Metaschoepite has been synthesized in the presence of neptunium(V) over the pH range modeled in the proposed Yucca Mountain geologic repository. Uranium (VI) phases were synthesized by varying pH and neptunium concentrations. Results of neptunium association with the uranium alteration phases are presented and the relationship to dissolved neptunium concentrations discussed.
A Radiochemical Analyses of Metastudtite and Leachates from Spent Fuel
Authors: McNamara Bruce , Hanson Brady , Buck Edgar , Soderquist Chuck 
Published: April 2011

AbstractWe have characterized considerable amounts of the two known uranyl peroxide phases that formed under static immersion conditions on commercial spent nuclear fuel (CSNF) samples. Milligrams of corroded fuel aggregates were observed at the air-water interface in each sample. The bulk fuel and the interfacial solids were examined by SEM, EDX, and XRD and were found to contain studtite and metastudtite, respectively. The reason for the partitioning of the two phases is not clear at this time. The unique occurrence of the floating phase prompted a radiochemical analysis of these solids. The analysis indicated that 90Sr, 137Cs, 99Tc, and to a lesser extent of 238,239Pu and 237Np, had partitioned with the air-water interface aggregates. The concentration of 241Am in the interfacial solids was two orders of magnitude lower than the inventory in the fuel prior to contact with water. The radiochemical analyses of two fuel leachate samples are compared to reported leaching data of a similar fuel which did not result in the formation of studtite.
Finite Element Analysis of Elastic and Plastic Deformation during Growth of Si1−xGex/Si Heterostructures
Authors: Karoui F. Sahtout , Karoui A. , Rozgonyi G. 
Published: April 2011

AbstractThe elastic and plastic stress distribution in strained Si1−xGex heterostructure (x=0.2 and x=0.5), was investigated during the growth process using a nonlinear transient finite element modeling. The material plastic behavior is described by the von Mises yield criteria coupled with isotropic work hardening conditions. The calculated stress distribution during growth of the SiGe cap layer shows that the von Mises stress fluctuates strongly within the layers and at the interfaces. The surface of constant composition Si1−xGex layer is found under compressive stress in both cases. Within that layer the normal stress in the growth direction remains compressive for x=0.2, while it changes from compressive to tensile for x=0.5. In the graded layer the stress goes from tensile to compressive for x=0.5 and in the opposite way for x=0.2. High plastic deformation is observed in the layers, with the maximum von Mises plastic stress being higher for x=0.5 and localized in the SiGe graded region. The plastic strain vanishes monotonically up to 8 μ deep into the Si bulk substrate, in agreement with TEM images that revealed dislocation loops penetrating into the substrate. The time dependent analysis shows that elastic and plastic deformation appear almost instantaneously in the sublayers, while in the Si substrate it is delayed up to 300 s.
A New MSE Curriculum
Authors: Roylance David 
Published: April 2011

AbstractThe MSE Department at MIT has developed a new undergraduate curriculum, and has imple- mented it for Sophomores in the 2003-2004 academic year. The Junior and Senior year curricula will be implemented as the current Sophomores advance. In addition to major core topic addi- tions such as biomaterials and computational modeling, the new curriculum features a novel mixing of laboratory and lecture hours. This permits students to experience hands-on applications of materials in the laboratory immediately after covering the associated theory in lecture. The curriculum was developed in consultation with both students and our external community (Visiting Committee, ABET, alumni), and it required construction of substantial new laboratory facilities. It also required a novel approach to scheduling, in which some loss of flexibility was accepted to gain coherence and relevance of topics.
A Way to Get Students Interested in Materials Science: Research Presentations for the K-12 Group
Authors: Martínez-Miranda L. J. 
Published: April 2011

AbstractThe GK-12 program involves students doing a masters or a Ph.D. in science and engineering working with a science teacher to develop demonstrations and laboratories which will bring the excitement of science into the schools. They work for an entire semester with the same group in school. We expect that the teachers will be able to carry on these demonstrations after the GK-12 students have left. Another aspect we want to bring to the students is the excitement of doing research in the field, and that what they are learning may be helpful in doing this research. As part of their work, we ask the GK-12 participants to prepare a research presentation for their schools. They have to present it in language that the students will understand, and with the material that the students have learned. In doing this, the students learn how to explain their research in much better terms and the K-12 students are exposed to real research and new approaches that nonetheless are based in the lessons they are learning.
Nanotechnology Summer Undergraduate Research Intern Program: Comprehensive Introduction to Life as a Researcher
Authors: Melloch M.R. , Lax J. 
Published: April 2011

AbstractWe have implemented a summer undergraduate research intern (SURI) program, the purpose of which is to give the undergraduates as real a picture as possible of what it is like to be a research scientist and what will be encountered in graduate school. Our first SURI class, the summer of 2003, consisted of a diverse group of 18 students from 9 different universities. Each student joined an ongoing cross-disciplinary research project team comprised of faculty and graduate students who have been working on research projects throughout the year. Coordinated with the students' research project was a technical writing/presentation course. The SURIs also participated in professional development activities, short courses, and a molecular conduction workshop. The culmination of the students' research and the technical writing/presentation course was a one-day conference at the end of their program in which all the SURIs presented the results of their summer research.
Shape Memory Alloys for Classroom Demonstrations, Laboratories, and Student Projects
Authors: Chen Katherine C. , Crone Wendy C. , Voss Eric J. 
Published: April 2011

AbstractShape memory alloys (SMAs) are unique materials that effectively capture the attention of students due to their dramatic phase transformations that result from temperature or stress. The fascinating properties and intriguing applications of SMAs can entice students to learn about the materials field, as well as relatively complicated materials concepts. SMAs have been incorporated into a range of courses under a variety of topics, such as crystal structures, phase transformations, kinetics, constitutive relations, and smart materials. The concepts can be presented at different levels of knowledge, appropriate to the learning objectives for the particular audience. Several educational activities using NiTi shape memory alloys have been developed, such as web-based videos, shape setting of new designs, classroom demonstration of actuation, visualization of stress-induced transformations, and heat treatments to change transformation temperatures.
Multiplexed Electrical Detection of Single Viruses
Authors: Zheng Gengfeng , Patolsky Fernando , Lieber Charles M. 
Published: April 2011

ABSTRACTWe report direct, real-time electrical detection of single virus particles with high selectivity using nanowire field effect transistors. Measurements made with nanowire arrays modified with antibodies for influenza A showed discrete conductance changes characteristic of binding and unbinding in the presence of influenza A but not paramyxovirus or adenovirus. Moreover, simultaneous electrical and optical measurements using fluorescently-labelled influenza A demonstrate conclusively that the conductance changes correspond to binding/unbinding of single viruses at the surface of nanowire devices. In addition, studies of nanowire devices modified with antibodies specific for either influenza or adenovirus show that multiple viruses can be selectively detected in parallel. The possibility of large scale integration of these nanowire devices suggests potential for simultaneous detection of a large number of distinct viral threats at the single virus level.
Sensing Properties of CNT hybrid MOS-based Sensors
Authors: Liou Wei-Jen , Yang Tsung-Yeh , Lin Kuang-Nan , Yang Ching-Hong , Lin Hong-Ming 
Published: April 2011

ABSTRACTThe carbon nanotubes provide large surface that can enhance the gas adsorption properties and increase the conductivity at a lower temperature for gas sensing. The gas sensing properties of the hybrid TiO2/CNTs material are examined in this study. The sol-gel technique is used to prepare a thin layer of nano-TiO2 coated on CNTs. The structure of TiO2/CNTs hybrid materials is identified by X-ray diffraction (XRD) and Raman spectrum. The granules and surface morphology are analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrical properties of the hybrid TiO2/CNTs indicate that the operation temperature can be lowered to ambient temperature and this will enhance the gas sensitivity for detecting CO gas. The n-type or p-type behavior of hybrid TiO2/CNTs can be controlled by the coating thickness of hybrid TiO2. According to the image results, the mechanisms of the n-type and p-type behavior of hybrid TiO2/CNTs system are proposed.
Sr(Ti, Fe)O3-δ Exhaust Gas Sensors
Authors: Schneider Thomas , Peters Christoph , Wagner Stefan , Menesklou Wolfgang , Ivers-Tiffée Ellen 
Published: April 2011

ABSTRACTSr(Tix, Fe1-x)O3-δ solid solutions were found to change their temperature coefficient of resistance (TCR) from negative to positive as iron increasingly substitutes for titanium, with the TCR tending towards zero at × = 0.35. This composition, Sr(Ti0.65Fe0.35)O3-δ thus shows temperature independent characteristic.For the development of a planar type sensing element for automotive applications, Sr(Ti, Fe)O3-δ has to be applied as a thick film. To confirm the sensor characteristic temperature independence (at T = 750…950 °C, p O2 = 10−5…1 bar) and fast response times (t90 = 6.5 ms at 900 °C), both key issues of Sr(Ti, Fe)O3-δ, thick film sensors have to be maintained over the entire lifetime. In this work, the structural and electrical properties of the sensor are investigated with regard to the chemical stability of the sensing element.
High Temperature Operation and Stability of Langasite Resonators
Authors: Fritze H. , Schulz M. , Seh H. , Tuller H. L. 
Published: April 2011

ABSTRACTFactors limiting potential use of langasite as a gas sensor platform at elevated temperatures include excessive conductive and viscous damping, deviations from stoichiometry and chemical instability. This paper focuses on viscous damping which can be described by an effective viscosity of the resonator material. Based on a one-dimensional description of the resonator device, the material constants of langasite are determined as a function of temperature. Theeffective viscosity of the resonator material and the bulk conductivity are found to exhibit nearly the same activation energy at temperatures from 350 to 600 °C. Based on that fact, it is most likely that the predominant conduction mechanism, i.e. oxygen ion movement, controls the viscous damping in that temperature range. Therefore, intentional doping must suppress the oxygen conductivity to minimize losses. The effect of such dopants is presently under investigation. Further, pre-annealing specimens for several hours above 1050 °C is necessary, for the given sample dimensions, to establish reproducible materials properties. Based on oxygen diffusion data, it can be concluded that the oxygen stoichiometry of langasite specimens becomes equilibrated during the pre-annealing runs.
Performance of a MIS Type Pd-Cr/AlN/Si Hydrogen Sensor
Authors: Zhang Linfeng , Al-Homoudi Ibrahim A. , Rahman H. , McCullen Erik F. , Rimai Lajos , Baird Ron J. , Naik Ratna , Newaz Golam , Auner Gregory W. , Simon Ng K. Y. 
Published: April 2011

ABSTRACTAn MIS Hydrogen sensor with a Pd0.96Cr0.04/AlN/Si structure was fabricated, exhibiting the dynamic range considerably wider than that of analogous devices with pure Pd gates. A useful response could be obtained for Hydrogen concentrations as large as 50, 000 ppm. Although the response amplitude was much reduced at the lower concentrations, satisfactory signal to noise down to 50 ppm could be obtained. The saturating magnitude of the electrical response is in the range of 0.1 to 0.5 V, which is the same as that for the pure Pd gated devices, inspite of the 3 orders of magnitude difference in the saturation hydrogen concentration. This result will be discussed in terms of the response mechanism of these devices.
Vitreous Chalcogenide Semiconductors for Gas Sensing Application
Authors: Dmitriev Serghei V. , Dementiev Igor V. 
Published: April 2011

ABSTRACTReport presents results of research aimed the investigation of possibility to use such chalcogenide materials as vitreous As2S3, As2Se3 and their solid solutions for gas sensors applications. For a long time these materials were well-known as materials mostly used for optical information registration. Developed approach allows to widening the sphere of application of given materials and create new class of gas sensitive devices.Thin film gas sensitive elements on the base of solid solutions of (As2S3)x-(As2Se3)1−x (where x=0; 0.3; 0.5; 0.7 and 1.0) were obtained by means of the thermal evaporation under vacuum conditions 10−5 Torr. Thin films can be deposited on both hard and flexible substrate. Formed films had specific resistance on the level 1010–1014 Ohm.cm (on dependence on composition) at the thickness of 1–2 μm.It was established that CGS thin films possess gas sensitivity S, determined as S=(Ggas-Gait)/Gair, on the level 2–3 relative units for CO and 7–8 for hydrogen at the 100 ppm concentration levels of both gases in atmosphere already at the room temperature that allows to excluding the heater from the gas sensor construction decreasing through that both manufacturing and operational cost.It is concluded that chalcogenide semiconductor materials can be considered as perspective materials for gas sensor application, including space exploration application.
Influence of Thermal Treatments on the Chemistry and Self-Assembly of Ge Nanoparticles on SiO2 Surfaces
Authors: Stanley Scott K. , Coffee Shawn S. , Ekerdt John G. 
Published: April 2011

ABSTRACTGeH4 is thermally cracked over a hot filament depositing 0.7–15 ML Ge onto 2–7 nm SiO2/Si(100) at substrate temperatures of 300–970 K. Ge, GeHx, GeO, and GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300–1000 K. Ge bonding changes are analyzed during annealing from 300–1000 K with X-ray photoelectron spectroscopy (XPS). Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 decomposition to Ge through high temperature pathways is seen above 700 K. Germanium oxidization results from Ge etching of the oxide substrate, which is demonstrated through XPS. Ge nanoparticle formation on SiO2 is demonstrated using the agglomeration process. With these results, explanations for the difficulties of conventional chemical vapor deposition to produce Ge nanocrystals on SiO2 surfaces are proposed.
Device Structures and Charicterization of one Tansistor Ferroelectric Memory Devices
Authors: Li Tingkai , Hsu Sheng Teng , Ulrich Bruce , Evans Dave 
Published: April 2011

ABSTRACTOne-transistor (1T) memory devices with MFIS (Metal, Ferroelectrics, Insulator, Silicon) and MFMIS (Metal, Ferroelectrics, Metal, Insulator, Silicon) structures have been widely studied. These memory devices exhibit memory working functions but very poor retention properties. Three possible mechanisms are responsible for the poor retention of 1 T ferroelectric memories: namely, charges trapping within the gate oxide and ferroelectric film, floating gate effect, and the depolarization field. In order to overcome these problems, a novel ferroelectric transistor design using a semiconductive oxide film in place of the gate dielectric has been fabricated. The device structures are Pt/PGO/InO2/Si (MFSoxS) and Pt/PGO/Ir/InO2/Si (MFMSoxS). There is no insulator in the gate stack. These device structures do not have floating gate and the depolarization field is very low. Therefore, the memory retention time can be very long. In this paper, we report the device structures, integration processes and the working properties with improved retention properties of the Pt/PGO/InO2/Si (MFSoxS) and Pt/PGO/Ir/InO2/Si (MFMSoxS) devices.
δ-Nb-doping Effect to The Interface Between IrO2 Top Electrode and Pb(Zr, Ti)O3 by Metal Organic Chemical Vapor Deposition
Authors: Matsuura Osamu , Yamawaki Hideki , Nakabayashi Masaki , Horii Yoshimasa , Sugiyama Yoshihiro 
Published: April 2011

ABSTRACTWe studied the Nb doping effect on the electrical characteristics of MOCVD-PZT capacitors using uniformly Nb-doped Pb(Zr, Ti)O3 (UND-PZT) and δ-Nb-doped PZT (DND-PZT) prepared by MOCVD. The 2Pr for UND-PZT was small and the UND-PZT hysteresis shifted in a positive direction. However, the 2Pr for DND-PZT decreased by only 5.5% and the hysteresis of DND-PZT didn't shift. In addition, the leakage current of DND-PZT decreased by one order at low bias compared to non-doped PZT, because the δ-Nb-doping layer maintains the barrier height, higher than that of none-doped PZT due to defect compensation. As a result, Nb1% DND-PZT was well suited to use Nb doping which decreases leakage current at low voltage and maintains 2Pr.
Quantifying the Role of Electronic Charge Trap States on Imprint Behavior in Ferroelectric Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) Thin Films
Authors: Lew Connie , Thompson Michael O. 
Published: April 2011

ABSTRACTPoly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric thin films are a potentially promising material for sensors or non-volatile memories. Imprint, the time-dependent resistance to polarization reversal, is a key material property that limits applications and is poorly understood. Based on experimental time and temperature dependences, we propose and investigate the link between imprint and charge trap states. A novel fast-ramp thermally stimulated current (TSC) measurement was developed to quantify and characterize the traps in an appropriate time-frame.Thin films of P(VDF-TrFE) on oxidized Si substrates were characterized following controlled initialization, fatigue, polarization, and imprint. Trap states were thermally filled/emptied by temperature cycling between 20–100 °C, using heating and cooling rates between 1 and 5 °C/s. Dynamics of this fast-ramp TSC indicate the presence of not only trap states, but also reversible and non-reversible charge accumulation. The presence of electrically active traps were verified by measurements over 1–10 s imprint times. Trapped charge directly correlated with the log of the imprint time, with a rate of ∼0.12 /μC/cm2/decade.
Dielectric and fatigue properties of Pb(Zr0.53Ti0.47)O3 thin films prepared from oxide precursors method
Authors: Shibatta-Kagesawa Silvia T. , Guarany C. A. , Araújo E. B. , Oki N. 
Published: April 2011

ABSTRACTFatigue is an important problem to be considered if a ferroelectric film is used for non-volatile memory devices. In this phenomena, the remanent polarization and coercive field properties degrades in cycles which increase in hysteresis loops. The reasons have been attributed to different mechanisms such as a large voltage applied on ferroelectric film in every reading process in Ferroelectric Random Access Memory (FeRAM) or memories for digital storage in computer, grain size effects and others. The aim of this work is to investigate the influence of the crystallization kinetics on dielectric and ferroelectric properties of the Pb(Zr0.53Ti0.47)O3 thin films prepared by an alternative chemical method. Films were crystallized in air on Pt/Ti/SiO2/Si substrates at 700°C for 1 hour, in conventional thermal annealing (CTA), and at 700°C for 1 min and 700°C 5 min, using a rapid thermal annealing (RTA) process. Final films were crack free and presented an average of 750 nm in thickness. Dielectric properties were studied in the frequency range of 100 Hz – 1 MHz. All films showed a dielectric dispersion at low frequency. Ferroelectric properties were measured from hysteresis loops at 10 kHz. The obtained remanent polarization (Pr) and coercive field (Ec) were 3.7 μC/cm2 and 71.9 kV/cm respectively for film crystallized by CTA while in films crystallized by RTA these parameters were essentially the same. In the fatigue process, the Pr value decreased to 14% from the initial value after 1.3 × 109 switching cycles, for film by CTA, while for film crystallized by RTA for 5 min, Pr decreased to 47% from initial value after 1.7 × 109 switching cycles.
Perfectly c-axis oriented epitaxial lead titanate thin film deposited by a hydrothermal method for a data storage medium
Authors: Morita Takeshi , Cho Yasuo 
Published: April 2011

ABSTRACTA hydrothermal method is a unique method to deposit ferroelectric thin films utilizing chemical reaction in solutions. In addition to the low reaction temperature below 200°C, its simple process procedure, automatically aligned polarization and a three-dimensional deposition are advantages. In this study, a lead titanate epitaxial thin film was obtained on a strontium ruthenate bottom electrode sputterd on strontium titanate (100). The highresolution X-ray diffraction mapping showed the film was perfectly c-axis oriented. The transmission electron microscope observation revealed that the film had no lattice dislocation at the interface between lead titanate and strontium ruthenate. A remanent polarization of 96.5μC/cm2 was measured with the single crystal-like DE hysteresis curve. The observation of a scanning nonlinear dielectric microscopy indicated that this film did not contain any defect such as an a-domain and a grain boundary even on the nano scale. With various pulse parameters, nano-domain dots were patterned and the minimum dot radius of inverted domain was 12 nm corresponding to data storage density of 1Tbit/inch2.