bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure-property relationships of Au films electrodeposited on Ni
Authors: Marchi C. San , Moody N.R. , Cordill M.J. , Lucadamo G. , Kelly J.J. , Headley T. , Yang N.
Published: April 2011

Thin gold films and coatings on metal have long constituted an important technology for the microelectronics industry and will continue to be important for microdevices such as contact springs. The properties of these materials may be highly processing dependent, particularly when the gold is deposited by electrochemical means. In this study, we characterize gold electrodeposited on Ni substrates from two bath chemistries: hard Au sulfite with proprietary hardening additive and soft Au cyanide. TEM and SEM show that the bath chemistry alters the microstructure and the resulting surface of the electrodeposits. Nanoindentation techniques were used to determine the elastic and plastic properties of the Au electrodeposits as a function of the specifics of processing. Soft Au electrodeposits have a grain size of on the order of 300 nm and a hardness of about 1 GPa. Hard Au electrodeposits produced from the sulfite bath feature grain sizes as small as 30 nm, some twinning, and fine porosity uniformly distributed both within the grains and at grain boundaries. The hardness is about 2 GPa, approaching the hardest values reported for sputtered gold films. The effect of the hardening agent on the microstructure of electrodeposits from the Au sulfite bath was also investigated and found to significantly refine the grain size at concentrations of at least 4 mL/L, although little additional refinement was found at higher concentrations.
Elevated Temperature Mechanical Properties of Devitrified Metallic Glass
Authors: Mara Nathan A. , Sergueeva Alla V. , Mukherjee A.K.
Published: April 2011

Elevated temperature tensile tests of different microstructures arising from different heat treatments of the Fe-based metallic glass Vitroperm (Fe73.5Cu1Nb3Si15.5B7) are presented. An anneal at 600°C for 1h yields a single phase μ-Fe microstructure with equiaxed, randomly oriented 15 nm grains, which is an ideal candidate for study of material properties at diminishing length scale. This microstructure has good stability during tensile testing at 600°C, showing a strain rate exponent correlating to grain boundary sliding (m=0.5), but little ductility, and strengths to 1250 MPa. The brittle behavior could be attributed to the lack of dislocation activity at such length scales. At temperatures up to 725°C, grain growth occurs, leading to elongations as large as 65% at flow stresses of 250 MPa. Precipitation of a second Nb-rich phase accompanies the grain growth. This investigation is supported by NSF, Division of Materials Research, grant NSF-DMR-0240144.
Thermomechanical properties and fatigue of nanocrystalline Ni/Cu electrodeposits
Authors: Arnould Olivier , Hubert Olivier , Hild François
Published: April 2011

This study deals with the long-term reliability of a high precision pressure sensor using bellows mainly made of electroplated Ni. Thermomechanical properties of this deposit are obtained by several experiments and compared to theoretical models, computations and other authors' results. Bellows are expected to stay in service for many decades, thus their high cycle fatigue behavior has to be known. Stress-life fatigue curve for crack initiation and fatigue crack growth in the electroplated Ni are measured and identified using numerical computations. Results are compared with other results obtained on similar Ni electrodeposits. Normalized stress-life fatigue curve shows no specific nanosize effects.
Deformation and Failure of Nanostructured Materials with Bimodal Grains
Authors: Ye R.Q. , Han B.Q. , Lavernia E.J.
Published: April 2011

The low ductility of nanostructured materials is attributed to the deficit of dislocation activity in the nanometer range. Recent scientific interest in nanostructured materials stems from reports of alterative combinations of mechanical properties, although a low ductility is typically reported. One promising approach based on the concept of multiple length scales is illustrated by a “bimodal” microstructure, i.e. containing a mixture of nanostructured and coarse grains. The present work reports a numerical study of the tensile deformation and fracture of a nanostructured Al alloy with a bimodal microstructure. In the theoretical framework used in the present study, the elastic-plastic behavior and deformation processes are approximated by Ramberg-Osgood formula and finite element method, respectively. The numerical results are found to be in a good agreement with the experimental behavior.
Stress Distribution in Ultra Thin SiO2 Film/Si Substrate System Measured by a Low Level Birefringence Detection Technique
Authors: Liu X. H. , Peng H. J. , Wong S.P. , Zhao Shounan
Published: April 2011

In this work, a low level birefringence detection system was employed to study the stress distribution in Si substrate induced by thermally grown ultra-thin SiO2 film. According to traditional bi-metallic strip theory, it is expected that the stress should show a linear dependence on depth with the zero stress plane located at the position of two third of the thickness of the substrate from the SiO2/Si interface. The linear dependence of stress on depth in accordance with the bi-metallic strip theory was observed only in part of the substrate. For the region below the SiO2/Si interface extending to a depth of about 1/5 of the thickness of the substrate, the magnitude of the stress was found to be significantly smaller than expected. The position of the zero stress plane was found to depend on the thickness of the SiO2 film and the oxidation conditions. The zero stress plane seemed to move towards the bottom of the Si substrate as the thickness of the SiO2 film became thinner and no zero stress plane was observed in the Si substrate when the SiO2 films became sufficiently thin.
Microstructural Refinement in Steels by Machining
Authors: Swaminathan S. , Swanson C. , Brown T. L. , Kezar R. F. , Chandrasekar S. , Compton W. D. , Trumble K. P.
Published: April 2011

A study has been made of microstructure and hardness of machining chips created from commercially pure iron and carbon steels. Large shear strains imposed during chip formation in machining are found to produce significant microstructure refinement in the chips, resulting in higher hardness compared to the bulk. Transmission electron and scanning electron microscopy have shown the chips to consist entirely of ultra-fine grain structures with ferrite grain sizes in the range of 100-800 nm. With high carbon steels, the microstructure of the bulk material prior to machining is also seen to have a significant influence on the characteristics of the chip.
Preparation of A New Carbon Nano-particle by Arc Discharge
Authors: Li Bean-Jon , Kung Sheng-Chin , Hsu Chih-Ming , Gao Jhy-Yeong , Lai Hong-Jen
Published: April 2011

Synthesis and characterization of a new carbon particle are investigated in this study. The carbon particle, which possesses a very high surface area (682 cm2/g), is suitable for catalysts loading in application of fuel cell. As well known, carbon materials are used to be a support of Pt catalyst to achieve high dispersion to enhance the activity of Pt. The synthesis was performed by conventional arc discharge process between two graphite electrodes in vacuum. A high-current range from 100∼ 300 ampere was utilized to evaporate the cathode electrode in order to produce carbon soot onto the wall of chamber, and further high production rate of 10 g/hr was achieved. The morphology and microstructure of the materials were investigated by SEM, HRTEM, XRD and Raman spectroscopy.

Observations of the soot by SEM and HRTEM have shown that it consists agglomerations of carbon particles linked each other to form a chain-like structure. Most carbon particles are approximate 30 ∼ 60 nm in diameter. HRTEM observation reveals that a carbon particle is comprised of several defective onions with different diameters and extremely curled graphene sheets, which appear as double-sheet layers.
Assemblies of Semiconductor and Metal Nanoparticles for Renewable Energy
Authors: Markarian Marie Zabel , El-Harakeh Maysaa , Makki Rabieh , Halaoui Lara I.
Published: April 2011

Nanostructured electrodes were assembled layer-by-layer from polyacrylate-capped Pt nanoparticles (=2.5 ± 0.6 nm) in a cationic polyelectrolyte. Cyclic voltammetry revealed hydrogen adsorption peaks at the modified nanoparticles characteristic of an activated polycrystalline Pt surface, with a negative shift in the peak potentials indicating a less facile electro-adsorption relative to the polycrystalline electrode, possibly due to nanoparticle surface modification. Current-voltage measurements at multilayers of Pt nanoparticles in polyelectrolytes indicated the feasibility of charge hopping between the particles embedded in the insulating matrix. Such feasibility was also evidenced in photoluminescence quenching of Q-CdS dots (=3.6 ± 0.5 nm) assembled in polyelectrolytes upon inserting Pt nanoparticles in the architecture.
Primary osteoblasts adhesion onto RGD-functionalized and cross-linked polyelectrolyte multilayer films
Authors: Picart Catherine , Richert Ludovic , Elkaim René , Schaaf Pierre , Voegel Jean-Claude , Frisch Benoît
Published: April 2011

The adhesion of primary osteoblastic cells on top of biocompatible polyelectrolyte multilayer (PEM) films was investigated for native films and after changing the films properties either with a chemical stimulus (film functionalization), with a mechanical stimulus (film cross-linking), or with both stimuli combined. For the functionalization, a 15 amino acid peptide containing a –RGD- (-Arg-Gly-Asp) sequence was grafted to poly(L-glutamic) acid and deposited on top of poly(L-lysine)/poly(L-glutamic) (PLL/PGA), PLL/Poly(alginic), and PLL/Poly(galacturonic) films. The film buildup and the adsorption of the PGA-RGD was followed by Optical Waveguide Lightmode Spectroscopy and by Atomic Force Microscopy. The mechanical stimulus was achieved by crosslinking the films with a water soluble carbodiimide (EDC) in combination with N-hydroxysulfo-succinimide (sulfo-NHS) to induce amide formation. Fourier Transform Infrared Spectroscopy evidenced the conversion of amine and carboxylic groups into amide groups.

The alkaline phosphatase (ALP) activity test was used to assess osteoblast adhesion and proliferation on top of the different films over a period of eight days in culture. Whereas the native films are poorly adherent, the RGD-functionalized films exhibit an increased short time adhesion. The native films could also be successfully cross-linked thereby dramatically enhancing cell proliferation. The cells did not react similarly on the different types of films investigated : the cross-linked (PLL/Palg) and (PLL/Pgal) films were much more efficient than the native or functionalized films in terms of proliferation. On the other hand, for the (PLL/PGA) films, functionalization and film cross-linking had a similar long term effect. Very interestingly, for these latter films, both stimuli could be combined.
Surface Engineering of Nano-fibrous Biodegradable Poly(L-lactic acid) Scaffolds for Tissue Engineering
Authors: Liu Xiaohua , Won Youngjun , Ma Peter X.
Published: April 2011

The architectural design and surface properties of scaffolds are important aspects in tissue engineering. The porous scaffolds accommodate cells and guide their growth, while the surface nature of the scaffolds can directly affect cell attachment, proliferation, and ultimately neo tissue regeneration. In this work, a highly porous poly(L-lactic acid) (PLLA) scaffold with nano-fibrous pore wall architecture has been fabricated by mimicking the structure of natural collagen using a novel thermally induced phase separation method developed in our group. A universally effective surface modification method was developed, and gelatin was successfully grafted onto the surface of nano-fibrous PLLA scaffolds by entrapment procedure. The surface composition, morphology, and properties were examined using ATR-FTIR, XPS and SEM. The surface coverage of gelatin on the PLLA surface was as high as 39.4%. MC3T3-E1 osteoprogenitor cells were cultured for 6 weeks in solid-walled PLLA scaffolds, nano-fibrous PLLA scaffolds, and surface-modified nano-fibrous PLLA scaffolds, respectively. The osteoblasts proliferated in all three types of scaffolds, but the cell numbers were always significantly higher in the surface-modified nano-fibrous scaffolds than in the other two types of scaffolds, and the cell numbers in nano-fibrous scaffolds were higher than that in the solid-walled scaffolds. These results demonstrate that the surface-modified nano-fibrous architecture could serve as a superior scaffold for tissue engineering.
Perturbed Amelogenin Protein Self-assembly Alters Nanosphere Properties Resulting in Defective Enamel Formation
Authors: Paine Michael L. , Lei YaPing , Luo Wen , Snead Malcolm L.
Published: April 2011

Dental enamel is a unique composite bioceramic material that is the hardest tissue in the vertebrate body, containing long-, thin-crystallites of substituted hydroxyapatite. Enamel functions under immense loads in a bacterial-laden environment, and generally without catastrophic failure over a lifetime for the organism. Unlike all other biogenerated hard tissues of mesodermal origin, such as bone and dentin, enamel is produced by ectoderm-derived cells called ameloblasts. Recent investigations on the formation of enamel using cell and molecular approaches have been coupled to biomechanical investigations at the nanoscale and mesoscale levels. For amelogenin, the principle protein of forming enamel, two domains have been identified that are required for the proper assembly of multimeric units of amelogenin to form nanospheres. One domain is at the amino-terminus and the other domain in the carboxyl-terminal region. Amelogenin nanospheres are believed to influence the hydroxyapatite crystal habit. Both the yeast two-hybrid assay and surface plasmon resonance have been used to examine the assembly properties of engineered amelogenin proteins. Amelogenin protein was engineered using recombinant DNA techniques to contain deletions to either of the two self-assembly domains. Amelogenin protein was also engineered to contain single amino-acid mutations/substitutions in the amino-terminal self-assembly domain; and these amino-acid changes are based upon point mutations observed in humans affected with a hereditary disturbance of enamel formation. All of these alterations reveal significant defects in amelogenin self-assembly into nanospheres in vitro. Transgenic animals containing these same amelogenin deletions illustrate the importance of a physiologically correct bio-fabrication of the enamel protein extracellular matrix to allow for the organization of the enamel prismatic structure.
Collagen-calcium Phosphate Composite Coatings by Electrolysis-induced Self-assembly and Mineralization
Authors: Fan Yuwei , Duan Ke , Wang Rizhi
Published: April 2011

A bone-like composite coating of collagen protein and calcium phosphate minerals is considered to be bioactive and may enhance bone growth and fixation of metallic orthopedic implants. In this study, we have successfully prepared a uniform collagen fibril/octacalcium phosphate composite coating on silicon substrate by electrolytic deposition. Under a typical deposition condition, a thin (100 nm) layer of calcium phosphate coating would form on the cathode (Si) surface first, which was followed by a thick (∼100 μm) composite coating. The porous composite layer consists of a collagen fibril network on which clusters of octacalium phosphate crystals nucleate and grow. The results not only provide a novel bioactive coating for biomedical implants, but also establish a new experimental protocol for studying biomineralization mechanisms of collagen based biological tissues.
Biological Modification in the Brushite Crystallization
Authors: Tang Ruikang , Darragh Molly R. , Orme Christine A. , Hoyer John R. , Nancollas George H.
Published: April 2011

The crystallization of brushite has been investigated in the presence of typical ionic biological components, magnesium, fluoride and citrate and a natural protein, osteopontin, using a constant composition method capable of nano-mole sensitivity. While the simple ionic additives, magnesium and fluoride do not have a significant effect, citrate ions can adsorb on lateral faces due to electrostatic interactions involving the functional carboxylate groups, resulting in crystal morphology changes. Osteopontin was the most effective inhibitor influencing the growth of virtually all brushite crystal faces.
Development of Self-assembled Muscle-powered Microdevices
Authors: Xi Jianzhong , Schmidt Jacob J. , Montemagno Carlo D.
Published: April 2011

As microcomponents in engineered systems, biological muscles have unique advantages such as large force transduction, utilization of biochemical fuel, and self-assembly from single cells, over other inorganic actuators for biomedical engineering applications. Successful integration of muscles with inorganic fabricated structures and electronics promises the capability of precisely characterizing muscles' mechanical properties and fabricating self-assembled controllable autonomous structures powered by ubiquitous glucose. However, the use of extracted muscle tissue from animals on these devices is impractical and inefficient, as the tissues must be dissected and incorporated into each device by hand with crude interfaces between the biological tissue and inorganic materials. Integration of muscle with fabricated structures would be optimally achieved through self-assembling muscle cells on MEMS. The construction of self-assembled muscle-powered MEMS structures is complicated by the stringent requirements to spatially direct the cell growth, control the tight connection of these differentiated structures with MEMS structures, and enable the cells and the integrated hybrid freedom to move. Conventional and soft photolithography techniques have been extensively employed to pattern the growth of a variety of cell types and investigate their interaction with substrate in the micrometer level. However, all studies are only suitable for patterning static cells on an immobile surface, so a novel system of spatially patterning the contractible cells must be developed to enable the cells and the integrated hybrid devices to be free to move.

We present a novel system of self-assembling myocytes on MEMS devices. This system has shown its capability of spatially and selectively directed growth and differentiation of myocytes into single muscle bundles, attachment of these functional bundles to MEMS structures, and the controlled partial release of the resultant hybrid devices. Two groups of self- assembled muscle-MEMS devices, force-measuring cantilevers and muscle-powered microrobots have been created. Here the further detailed studies of this system are discussed, especially the concept of the self-assembly and the material interfacial problems in this system.
Effect of Inhibiting Oxyanions on the Localized Corrosion Susceptibility of Waste Package Container Materials
Authors: Dunn D.S. , Yang L. , Wu C. , Cragnolino G.A.
Published: April 2011

The DOE is currently preparing a license application for the permanent disposal of high level radioactive waste at Yucca Mountain, Nevada. The proposed design of waste packages for the disposal of high level radioactive waste consists of an outer container made of Alloy 22, a corrosionresistant Ni-Cr-Mo-W alloy, surrounding an inner container made of Type 316 nuclear grade stainless steel. Under conditions where passivity is maintained, the uniform corrosion rate of Alloy 22 is slow and long waste package lifetimes are projected. However, the initiation of localized corrosion such as pitting or crevice corrosion may decrease waste package lifetimes. In this study the crevice corrosion susceptibility of Alloy22 was determined in chloride solutions with additions of oxyanions that are present in the groundwater at the potential repository site. When present in sufficient concentrations relative to chloride, nitrate, carbonate, bicarbonate, and sulfate inhibited pitting and crevice corrosion of Alloy 22.
Electron Microprobe Investigation of Ti-pyrochlore Doped with Pu-238
Authors: Zamoryanskaya Maria V. , Burakov Boris E.
Published: April 2011

polycrystalline sample of Ti-pyrochlore, (Ca,Gd,Hf,U,Pu)2Ti2O7, doped with approximately 8.7 wt.% 238Pu and 20.0 wt.% 238U, has been studied at different cumulative doses of alpha induced radiation damage using scanning electron microscopy (SEM) and quantitative electron probe microanalysis (EMPA). All analyses of 238Pu-doped Ti-pyrochlore were done for comparison with 239Pu-doped pyrochlore synthesized under similar conditions. Our results suggest that accelerated alpha-induced radiation damage affects not only the crystalline structure of 238Pu-doped pyrochlore, but also causes changes in the chemical composition of the pyrochlore, and as proposed, destruction of pyrochlore-U-Pu solid solution. Numerous inclusions of a separate U-oxide phase were found in the 238Pu-doped pyrochlore crystalline matrix. The inclusions were observed visually using SEM and increased as a function of the cumulative dose. Also, after a cumulative dose of 1.1 × 1025 alpha decays/m3 the pyrochlore became nearly amorphous and inclusions of Hf-Ti-Ca-O phase were found in the crystalline matrix. In all cases separate phases of U-oxide and Hf-Ti-Ca-O were localized in chemically inhomogeneous areas. The results obtained allow us to assume that under self-irradiation the amorphization of Ti-pyrochlore might be accompanied with destruction of single solid solution, (Ca,Gd,Hf,U,Pu)2Ti2O7, into several pyrochlore phases of different chemical composition and precipitation of some amount of Pu and U into separate oxide phases.
Correlation of Formation Enthalpies with Critical Amorphization Temperature for Pyrochlore and Monazite
Authors: Helean K.B. , Navrotsky A. , Lian J. , Ewing R.C.
Published: April 2011

Systematic studies of a series of RE-titanate pyrochlore single crystals determined the formation enthalpies, ΔH0f-ox, and the critical amorphization temperature, Tc, the temperature above which the crystal can no longer be amorphized. A negative linear correlation was observed between ΔH0f-ox and Tc. In general as the cation radius ratio, RA/RB, decreases the formation enthalpy becomes less exothermic, i.e. the pyrochlore structure becomes less thermodynamically stable while the susceptibilty to ion beam-induced amorphization decreases. The opposite relation, i.e. a positive linear correlation between ΔH0f-ox and Tc was observed for a series of REPO4 single crystals with both the monazite and xenotime structures. Both relations can be understood in terms of pyrochlore and orthophosphate crystal chemistry, their formation of point defects, and the role of ion-irradiation induced phase transformations.
The immobilization of chloride-containing actinide waste in a calcium phosphate ceramic host: ageing studies
Authors: Metcalfe B. L. , Donald I. W. , Scheele R. D. , Strachan D. M.
Published: April 2011

Immobilization of radioactive wastes arising from the pyrochemical reprocessing of Pu metal with calcium phosphate as the host material has been investigated. Initial studies in which non-active elements are substituted for the actinide elements present in the wastes demonstrated that effective immobilization of both the cations and chloride ions was achieved within the chlorapatite Ca5(PO4)3Cl, and spodiosite, Ca2(PO4)Cl, mineral phases produced during the solid state reaction between host and waste. Follow-up studies with radioactive simulated waste composed of CaCl2, PuCl3 and AmCl3have confirmed the viability of the process and the durability of the product in aqueous solution. More recently a study of the long-term radiological stability and chemical durability of the ceramic product has commenced in which accelerated ageing of the ceramic phases is being achieved through the replacement of the 239Pu (half life 24,360y) that is contained in the actual waste by the short lived isotope 238Pu (half life 86.4y). The preparation of non-active and active samples and the crystal phases formed in each system as determined with XRD are herein reported. Data are presented which show that there is no detectable change in the XRD pattern of the samples containing 238Pu after 532 days of ageing, corresponding to around 400 years of real time ageing employing 239Pu. The detailed effects of ageing on the crystal structure and on the chemical durability of samples in aqueous solution are reported.
Crystallisation Within Simulated High Level Waste Borosilicate Glass
Authors: Rose Peter B. , Ojovan Michael I. , Hyatt Neil C. , Lee William E.
Published: April 2011

The devitrification products of two simulated high level radioactive waste (HLW) glasses have been investigated. Magnox waste glass contained RuO2 as its primary crystal phase, Pd-Te inclusions, a Cr-, Fe- and Ni-rich spinel phase, a Si- and lanthanide-rich phase and also a Zr-rich phase which incorporated Ce and Gd. Upon heat treatment the glass developed a zektzerite-type phase, CeO2, a strontium molybdate (containing Nd and La) as well as a Si-rich phase. 75/25 glass, comprising a blend of reprocessing waste derived from UO2 and Magnox fuels, contained RuO2 as its primary crystalline phase, CeO2 and a Si- and Ru-rich phase. Heat treatment of this glass resulted in the growth of the CeO2 crystals, the development of a strontium molybdate (containing Nd and La) and a Si- and lanthanide-containing phase. A sodium lanthanum molybdate with a powellite-type structure formed on the surface of both glasses after heat treatment in air.
Long-term behavior of R7T7-type nuclear glass: Current state of knowledge and outlook
Authors: Gin S. , Godon N. , Ribet I. , Jollivet P. , Minet Y. , Frugier P. , Vernaz E. , Cavedon J.M. , Bonin B. , Quang R. Do
Published: April 2011

This article reviews current knowledge of the long-term behavior of R7T7-type glass during the thermal phase and in geological repository conditions (aqueous alteration). In interim storage R7T7 glass can be considered to conserve its integrity over time. In geological repository conditions, the mechanisms of glass alteration by water have been identified and parameter values have been assigned to the reaction kinetics for wide variations of the influential factors (temperature, pH, flow rate, S/V ratio, etc.). CEA has developed an operational model to obtain robust and reasonably conservative predictions of the glass quantities altered after disposal. Examples of applications of the operational model are discussed, future research topics are also proposed to consolidate this approach.
Fundamental Experiments on Permeability Change of Flow-path by Highly Alkaline Plume
Authors: Usui Hideo , Niibori Yuichi , Tanaka Koichi , Tochiyama Osamu , Mimura Hitoshi
Published: April 2011

In the geological disposal system, natural barrier contains many selective flow-paths. Since cement used for the repository construction alters the condition of groundwater to a highly alkaline pH of about 13, such hyperalkaline plume would affect permeabilities of the flow-paths. To obtain more reliable estimate on the migration of radionuclides released from the repository, we must consider the changes in flow-paths with time and/or in space.

In this study, the influence of highly alkaline plume on the permeability has been examined, considering also the direction of flow. In order to simulate the flow-paths, the amorphous silica particles were packed in the column, and the NaOH solution (0.1 M) was injected continuously at a constant flow-rate into the column at room temperature. The change in the permeability was traced, and the concentration of silicic acid in the eluted solution was measured by using the silicomolybdenum-yellow method. It was confirmed that the difference of pH values at the inlet and outlet of the column was negligibly small (pH=13.0).

The experimental results showed that the change in fraction dissolved with time strongly depended on a flow-rate and a flow-direction. However, in the relation between the permeability and the fraction dissolved, the permeability did not change in the range of up to 0.35 in fraction dissolved. The SEM images of particle surface showed that the inner pores of particle increased in size. This suggested that, in this range of fraction dissolved, the porosity between particles is almost retained, while each particle dissolves mainly through its inner pores. Moreover, the dissolution rate in the column flow system was considered as being remarkably limited by diffusion process, in comparison with that estimated from the batch test.
Initial Results From Dissolution Testing of Spent Fuel Under Acidic Conditions
Authors: Hanson Brady D. , Friese Judah I. , Soderquist Chuck Z.
Published: April 2011

Flowthrough dissolution tests using solutions with pH in the range 2 to 7 have been conducted on a moderate burnup Light Water Reactor spent fuel. Such low pH conditions have been modeled as possibly occurring in a failed waste package at the proposed repository at Yucca Mountain. The release oftotal uranium, 99Tc, 90Sr, 137Cs, and 239&240Pu were measured for up to 90% total reaction of the specimens. The reaction rates, determined both from the cumulative release and the release normalized to surface area, were found to decrease with increasing pH and with increasing extent of reaction. The implications to instantaneous release and long-term behavior ina geologic repository are discussed.
Magnetic Properties of GaN Layers Implanted by Mn, Cr or V.
Authors: Guzenko Vitaliy A. , Thillosen Nicolas , Dahmen Andre , Calarco Raffaella , Schäpers Thomas , Luysberg Martina , Houben Lothar
Published: April 2011

We report on magnetic properties of the GaN layers implanted with 3d transition metal ions. GaN layers grown by MOVPE on sapphire substrates, p- or n-doped, were implanted by Mn, Cr or V ions with a dose of 5×1016 cm−2 and implantation energy of 200 keV. Subsequently, a rapid thermal annealing in nitrogen atmosphere for 5 minutes at different temperatures (700°C – 1050°C) was performed. The magnetization as a function of magnetic field as well as the dependence on temperature revealed paramagnetic behavior for all samples. In addition, an antiferromagnetic coupling between implanted ions was found.
Spin Lifetime Tuning in Zincblende Heterostructures and Tions to Spin Devices
Authors: Cartoixà X. , Ting D. Z.-Y. , Chang Y.-C.
Published: April 2011

We present analytical expressions for the D'yakonov-Perel' spin relaxation rates under the combined action of bulk and structural inversion asymmetry for [111] zincblende heterostructures when terms up to linear and third order in k are included in the Hamiltonian. We see for [111] heterostructures that, under the right conditions, the lowest-order-in-k component of the spin relaxation tensor can be made to vanish for all spin components at the same time. We study how the inclusion of terms of higher order in k affects these results. We finally discuss a proposal for a resonant spin lifetime transistor (RSLT) using the spin lifetime tuning concepts presented above, where the characteristics of the [111] device give the designer an added degree of freedom on the direction of the injected spins.
What Constitutes Successful Undergraduate Research?
Authors: Inglefield Colin , Johnston Adam
Published: April 2011

Research has become a point of much greater emphasis in the undergraduate science curriculum within the past few generations of undergraduate students. However, there is not universal agreement upon what constitutes a successful undergraduate research program, and how degrees of success should be measured. A model for a successful program based principally on student ownership of research projects will be presented here. This approach is an attempt to give undergraduate students the most holistic research experience possible, by involving them in all stages of a research project in a limited amount of time. A central goal for each student is a definable product of their particular project, which is disseminated to as wide an external audience as possible. Measures of success, from student perspectives, will be discussed. These measures include data from interviews of students before and after their research experience.
An Approach to the Teaching of Functional Materials for Materials Science and Engineering Undergraduate Courses
Authors: Finlayson Trevor R. , Muddle Barry C.
Published: April 2011

Traditional materials science and engineering texts have, for the most part, focussed on instructing the undergraduate student on the physical properties of materials and providing a significant knowledge base from which, subsequently, to consider materials applications. With the increasing demand for professional materials scientists and engineers to embrace all classes of materials in their everyday applications, it is increasingly important for undergraduate teaching to increase the awareness of students to applications through a focus on functionality rather than just providing a thorough knowledge and understanding of material properties. This has become even more important in the area of “nanostructured” materials where functional devices are designed at the material fabrication stage. In this paper, recent experiences in the teaching of functional materials for electronic, thermal and optical applications, to a second level undergraduate student group, comprising both “science” and “engineering” students, are outlined and some initial outcomes from the assessment of the group discussed.
Near surface characteristics of highly sensitive metal oxide thin films
Authors: Kiriakidis G.
Published: April 2011

We present the gas sensing properties of InOx thin films deposited by dc sputtering and ZnOx thin films deposited both by dc sputtering and PLD. The sensitivity of the films towards ozone is correlated with the deposition parameters like film thickness, substrate deposition temperature and growth rate. Secondary Ion Mass Spectrometry (SIMS) analysis showed a noticeable deficit in oxygen in the top 5 nm for films in the “conducting” state, i.e., after UV exposure. Analysis of the sensing response for alumina-based transducers of InOx thin films revealed high sensitivity (less than 25 ppb) with fast and stable response towards ozone while ultimate sensitivity levels down to 10 ppb for ozone and 50 ppb for NO2 were achieved. Surface topography study of ZnOx films utilizing optical, AFM and SEM analyses has shown a distinct surface morphology variation correlated to the growth technique It is demonstrated that PLD leads to very rough surfaces with characteristic non-coordinated columnar features in contrast with the rather smooth surfaces obtained by sputtering.
FTIR Analysis of the Mechanisms of NOx Detection by Semiconductor Metal Oxide Nanoparticles
Authors: Baraton Marie-Isabelle , Merhari Lhadi
Published: April 2011

The chemical reactions occurring at the surface of tin oxide nanoparticles under NOx adsorption have been investigated by Fourier transform infrared spectroscopy and correlated with the variations of the electrical conductivity of tin oxide. These surface reactions have been found dependent on the particle size and on the presence of oxygen. The strong coordination of the newly formed chemical species onto the nanoparticle surface may result in a poor reversibility of the sensor response.
Effects of various annealing temperature on carbon nanotubes for N2 detection
Authors: Huang Chien-Sheng , Huang Bohr-Ran , Jang Yung-Huang , Hsieh Chih-Fu , Wu Chia-Ching , Chen Min-Chao , Yang Kun-Lin
Published: April 2011

The vertically aligned carbon nanotubes (CNTs) deposited by microwave plasma-enhanced chemical vapor deposition (MPCVD) were utilized as resistive gas sensors.

The carbon nanotubes were annealed between 200 to 800°C under N2 flow (500 sccm) for 15 minute, respectively. After that, the carbon nanotubes were exposed to an N2 filling and pumping environment. Upon exposure to N2 the electrical resistance of vertically aligned carbon nanotubes was found to increase. It was found that the N2 absorption of unannealed carbon nanotubes was reversible, whereas which of annealing ones was not. However, the sensitivity of the N2 absorption on carbon nanotubes was improved after annealing. From the Raman spectra, the ID/IG ratio of carbon nanotubes also decreased after annealing, indicating that more graphenes were formed by the annealing process. Furthermore, from X-ray photoelectron spectroscopy (XPS), it was observed that the ratio of the oxygen to carbon (O/C) signal intensity increased from 0.094 to 3.943 as the annealing temperature increased. As a consequence, it was suggested that the surface of carbon nanotubes was oxygenated and the absorption of N2 changed from physisorption to chemisorption.
Integration of microcatalysts on thin membrane for thermoelectric gas sensor devices
Authors: Choi Yeongsoo , Shin Woosuck , Tajima Kazuki , Izu Noriya , Matsubara Ichiro , Murayama Norimitsu
Published: April 2011

Dispenser technique was employed to integrate the Pt loaded on alumina (Pt/alumina) micro-catalysts on thin membrane of micro-thermoelectric hydrogen sensor (μ-THS). The μ-THS with Pt loaded alumina showed higher sensing performance than bulk-type THS with Pt thin film prepared by RF sputtering method. For the μ-THS with Pt/alumina catalyst, its voltage signal was 7.3 mV for hydrogen concentration of 1 % in dry air at catalyst temperature of 100 °C. In the case of the bulk-type THS with Pt thin film catalysts, the voltage signal was 0.33 mV under the same condition.
High-Temperature SiC MOSFET Gas Sensors
Authors: Matocha Kevin , Tilak Vinayak , Sandvik Peter , Tucker Jesse
Published: April 2011

Due to tightening restrictions on combustion exhaust emissions, low-cost sensors are desired for monitoring NOx production in high-temperature exhaust streams. This paper reports the characterization of Silicon Carbide MOSFET NO sensors for use in combustion exhaust monitoring. SiC depletion-mode MOSFETs were fabricated using a thermally-grown silicon dioxide gate dielectric and a Pt catalytic metal gate electrode. SiC MOSFET gas sensors were characterized at temperatures as high as 525°C in an ambient of synthetic air and NO (50–200 ppm) for 30 hours with no degradation.
Pulse Shape Study of Chemical Vapor Deposited Diamond Alpha Particle Detectors
Authors: Wang S. G. , Sellin P. J. , Lohstroh A. , Özsan M. E.
Published: April 2011

We report a study of pulse shapes of a radiation detector with a sandwich structure fabricated from chemical vapor deposited (CVD) polycrystalline diamond. The pulse shapes were recorded at room temperature using 5.486 MeV alpha particles from 241Am source. Only “fast” component was observed in the electron predominated pulses, whereas both “fast” and “slow” components were obtained in the hole predominated pulses, suggesting that electron charge drift is prompt and no detrapping occurred. In contrast, hole charge drift is slower than expected and trapping-detrapping took place during hole travel process.
Ferroelectric Thin Film Depositions for Various Types of FeRAMs (Ferroelectric Random Access Memories)
Authors: Fujisaki Yoshihisa , Ishiwara Hiroshi
Published: April 2011

Flash memories are now widely spread and conveniently used in mobile devices such as cellular phones, pagers, PDAs (Personal Digital Assistants), digital cameras and so on. And in the coming ubiquitous era, nonvolatile solid-state memories are expected to be more and more important for these mobile devices. However, Flash memories are not perfectly suitable for these mobile devices since their power consumptions are too high, writing speeds are two slow, programming endurances are limited up to 106 cycles. To resolve these problems, numbers of new nonvolatile solid-state memories are proposed and some of them are now under development. Among these newly emerging nonvolatile memories, FeRAMs (Ferroelectric Random Access Memories) are the only ones that are now in production. However, the process and materials to produce FeRAMs have not matured yet to support the ubiquitous technologies.

In this study, we explore the process technologies and materials required for the future FeRAMs and obtained the result that the requirements can be satisfied by the known technologies at present.
Non-volatile Thin Film Transistors Using Ferroelectric/ITO Structures.
Authors: Tokumitsu Eisuke , Miyasako Takaaki , Senoo Masaru
Published: April 2011

We report ferroelectric-gate thin film transistors (TFTs) using indium tin oxide (ITO) as a channel material. Bottom-gate structure TFTs have been fabricated using ferroelectric Pb(Zr, Ti)O3 (PZT) film as a gate insulator and ITO channel. Ferroelectric and ITO layers were formed by the sol-gel technique and RF sputtering, respectively. Drain current-drain voltage (ID-VD) characteristics of PZT/ITO ferroelectric-gate TFTs exhibit typical n-channel transistor operations with clear current saturation and electrical properties were improved by the post annealing. Drain current-gate voltage (ID-VG) characteristics demonstrate clear counterclockwise hysteresis loop due to the ferroelectric gate insulator. The obtained memory window is 2 V. The on/off current ratio of more than 102 has been obtained, which indicates that the ITO channel is sufficiently depleted by the ferroelectric polarization.
UV Assisted Rapid Thermal Processing of Strontium Bismuth Tantalate (SBT) Thin Films
Authors: O'Brien S. , Hurley P. K. , Crean G. M. , Johnson J. , Caputa C. , Wouters D.
Published: April 2011

A novel technique termed UV-assisted RTP has been developed and found to offer improvement in material properties, in particular when applied to thin films. Regarding crystallization of SBT, a number of UV-RTP strategies were developed and evaluated. It was demonstrated that UV irradiation of the sample material at a temperature in excess of the MOCVD deposition temperature was found to produce a significant increase in Pr.
Ge nanocrystals in MOS-memory structures produced by molecular-beam epitaxy and rapid-thermal processing
Authors: Nylandsted Larsen A. , Kanjilal A. , Lundsgaard Hansen J. , Gaiduk P. , Normand P. , Dimi-trakis P. , Tsoukalas D. , Cherkashin N. , Claverie A.
Published: April 2011

A method of forming a sheet of Ge nanocrystals in a SiO2layer based on molecular beam epitaxy (MBE) and rapid thermal processing (RTP) is presented. The method takes advantage of the very high precision by which a very thin Ge layer can be deposited by MBE. With proper choice of process parameters the nanocrystal size can be varied between ∼3 and ∼8 nm and the area-density between ∼1×1011and ∼1×1012dots/cm2. The tunneling oxide thickness is determined by the thickness of a thermally grown SiO2layer, and is typically 4 nm. C-V measurements of MOS capacitors reveal hole and electron injection from the substrate into the nanocrystals. Memory windows of about 0.2 and 0.5 V for gate-voltage sweeps of 3 and 6 V, respectively, are achieved.
Organic Memory Devices Using C60 and Insulating Polymer
Authors: Kanwal Alokik , Paul Shashi , Chhowalla Manish
Published: April 2011

In this paper, we describe an all organic molecular memory device that combines the advantages of molecular and organic electronics. We accomplish this by combining C60 molecules with poly(4-vinylphenol) (PVP) and co-dissolving them in iso-propanol. The current-voltage measurements show a large hysteresis in the blend devices, in contrast to pure PVP devices. The thin blend films have been thoroughly characterized using Raman spectroscopy, atomic force microscopy and scanning electron microscopy.
Microwave dielectric properties of oriented BaLa4Ti4O15 ceramics fabricated by templated grain growth
Authors: Fukami Yuko , Wada Kensuke , Kakimoto Ken-ichi
Published: April 2011

Dense and highly textured BaLa4Ti4O15 (BLT) ceramics was fabricated by templated grain growth method. Plate-like BLT particles prepared via a molten salt synthesis using NaCl flux were mixed with B LT powders obtained by the conventional solid state method. X-ray diffraction and scanning electron microscope studies of the textured ceramics showed plate-like BLT grains aligned parallel to the casting direction. Large anisotropy was found in the dielectric properties.
Evolution of Anisotropic Elastic Strains, and rf/Microwave Dielectric Properties of <110> Textured BST 60/40 Thin Films on <100> NdGaO3 Substrates
Authors: Simon W. K. , Akdogan E. K. , Bellotti J. A. , Safari A.
Published: April 2011

Ba0.60Sr0.40TiO3 thin films were deposited on orthorhombic <100> oriented NdGaO3 substrates by pulsed-laser deposition. Film thickness ranged from 25 nm to 1200 nm. X-ray pole figures have shown consistent <110> textured films with good alignement to the substrate. X-ray strain analysis indicates up to 0.5% compressive strain along the (001) direction, and weaker tensile strain along (-110). Dislocation densities, as computed from strain data, were found to be in the range 5–6×105 cm-1 along both directions. The critical thickness for dislocation formation along (001) and (-110) were found to be 5 and 7 nm, respectively. Permittivity and tunability were investigated using interdigitated capacitors in the 45 MHz-20 GHz range. Dielectric properties and tunability in the <110> oriented films exhibited strong strain and directional properties. Tunability up to 54% was observed at moderate field levels (∼ 5 kV/mm).
MEMS SiGe Technologies for RF and Millimeterwave Communications
Authors: Busquére J. P. , Do N. , Bougriha F. , Pons P. , Grenier K. , Dubuc D. , Schumacher H. , Abele P. , Rydberg A. , Ojefors E. , Ancey P. , Bouche G. , Plana R.
Published: April 2011

This paper shows the potentialities of merging the MEMS and micromachining with SiGe technologies in order to speed up the performances of next generation of front end in term of flexibility, reconfigurability and adaptability. MEMS technologies are presented based on Benzo-Cyclo-Butene (BCB) materials and Bulk Acoustic Wave (BAW) materials. Special attention is paid to ensure a full compatibility between IC and MEMS. We have shown that very innovative functions could be considered by using this MEMSIC concept.
Nonlinear magneto-optics of nanogranular films
Authors: Kim Evgenia M. , Murzina Tatyana V , Aktsipetrov Oleg A , Kravets Anatolii F.
Published: April 2011

In this paper, the results of experimental studies of magnetization-induced second- and third-order nonlinear optical effects in magnetic nanogranular films are described. Magnetization-induced variations of the intensity, polarization state and the phase of the harmonics' waves are observed in magnetic nanogranular films of the composition CoxAg1-x and Cox(Al2O3)1-x. Nonlinear magneto-optical Kerr effect (NOMOKE) in third-harmonic generation is observed in these nanomaterials. The second- and third-order NOMOKE from granular films is shown to exceed the linear magneto-optical Kerr effect by at least an order of magnitude.
Correlation of the Charge Storage and Magnetic Susceptibility of Hydrous RuO2
Authors: Swider-Lyons Karen E. , Bussmann Konrad M.
Published: April 2011

Hydrous RuO2 is a mixed metallic-protonic conductor that is used as a charge storage material in electrochemical capacitors and as an electrocatalyst. Previous structural analysis by Dmowski, et. al. has shown that RuO2 is a composite of ordered RuO2 nanoparticles that are surrounded by hydrous grain boundaries. In this paper, magnetic susceptibility (MS) is used to show that the hydrous RuO2 has both localized and delocalized electrons. The localized electrons are attributed to Ru3+ defects that decrease in concentration with decreasing water content. The delocalized electrons are represented by a temperature independent paramagnetic (TIP) component of the MS. The magnetic data is consistent with a structure having metallic nanoparticles whose electrons become more itinerant with decreasing structural water. We conclude that hydrous RuO2 stores charge analogously to double-layer capacitors in which charge is stored at the interface of the hydrous grain boundaries and the metallic nanoparticles, and that there is effectively no difference in the charge storage mechanisms of hydrous RuO2 and carbon.