bluuebunny/crossref_metadata_2025 huggingface dataset:
Microscopic Detection of DNA Hybridization using Miniaturized Diamond DNA-FETs
Authors: Nebel Christoph E. , Uetsuka Hiroshi , Yang Nianjun , Yamada Takatoshi , Watanabe Hideyuki
Published: April 2011

Miniaturized DNA sensitive field-effect transistors (DNA-FET) have been realized using single crystalline diamond grown by plasma-enhanced chemical vapor deposition (CVD). To bond DNA to diamond, amine linker-molecules are covalently attached by photochemical means to H-terminated diamond surfaces. Using hetero-bifunctional cross-linker and thiol-modified single-strand (ss) cancer marker DNA (CK20), the gate of diamond FETs is modified to sense hybridization of DNA, forming double-strand (ds) DNA molecules on the gate. The density of DNA bonded to diamond has been adjusted to about 1012 cm−2 and the experiments have been performed in phosphate buffer with different ionicity to control the Debye length of the Helmholtz layer. By hybridization, a gate-potential shift of 64 mV is detected in case of the 100 Å Debye lengths, while 46 mV is detected for 10 Å. This is discussed with respect to DNA related variations of charge and pH by hybridization. Time resolved experiments reveal exponential hybridization dynamics with a time constant of 600 s. The sensitivity limit of our experiment is about 1 nM.
Nanocrystalline Diamond as a Dielectric for SOD Applications
Authors: Bevilacqua Mose , Tumilty Niall , Chaudhary Aysha , Ye Haitao , Butler James E , Jackman Richard B
Published: April 2011

Nanocrystalline diamond (NCD) has been grown on oxide coated silicon wafers by microwave plasma assisted chemical vapour deposition using a novel seeding technique followed by optimised growth conditions, and leads to a highly-dense form of this material with grain sizes around 100nm for films approximately 1.5 microns thick. The electrical properties of these films have been investigated using Impedance Spectroscopy, which enables the contributions from sources characterised by differing capacitances, such as grain boundaries and grain interiors, to be isolated. After an initial acid clean the electrical properties of the film are not stable, and both grain boundaries and grains themselves contribute to the frequency dependant impedance values recorded. However, following mild oxidation grain boundary conduction is completely removed and the films become highly resistive (>1013 ohm/sq). This is most unusual, as conduction through NCD material is more normally dominated by grain boundary effects. Interestingly, the AC properties of these films are also excellent with a dielectric loss value (tan δ) as low as 0.002 for frequencies up to 10MHz. The dielectric properties of these NCD films are therefore as good as high quality free-standing (large grain) polycrystalline diamond films, and not too dissimilar to single crystal diamond, and are therefore ideally suited to future ‘silicon-on-diamond’ applications.
785 nm Raman Spectroscopy of CVD Diamond Films
Authors: May Paul William , Smith James A , Rosser Keith N
Published: April 2011

Raman spectroscopy is a powerful technique often used to study CVD diamond films, however, very little work has been reported for the Raman study of CVD diamond films using near infrared (785 nm) excitation. Here, we report that when using 785 nm excitation, the Raman spectra from thin polycrystalline diamond films exhibit a multitude of peaks (over 30) ranging from 400-3000 cm−1. These features are too sharp to be photoluminescence, and are a function of film thickness. For films >30 μm thick, freestanding films, and for films grown in diamond substrates the Raman peaks disappear, suggesting that the laser is probing the disordered small-grained interface between the diamond and substrate. Some of the peaks change in relative intensity with time (‘blinking’), and the spectra are very sensitive to position on the substrate – this is reminiscent of the behaviour seen in SERS spectra.
Theoretical Analysis of the Graphitization of a Nanodiamond
Authors: Kwon S. Joon , Park Jae-Gwan
Published: April 2011

A theoretical analysis of the nanodiamond graphitization was presented. Thermodynamic analysis of the nanodiamond showed three kinds of phase-diagram; smaller nanodiamond, nanodiamond-graphite, and larger nanodiamond. In the theoretical analysis, the most probable and the maximum volume fractions of graphite in the nanodiamond were 0.76 and 0.84, respectively regardless of the annealing temperature and the initial radius of the nanodiamond. The highest graphitization probability decreased with increasing annealing temperature.
The Origin of Field-induced Electron Emission from N-doped CVD Diamond Characterized by Combined XPS/UPS/FES System
Authors: Yamaguchi Hisato , Kudo Yuki , Masuzawa Tomoaki , Shiraki Yoshifumi , Saito Ichitaro , Kudo Masato , Yamada Takatoshi , Takakuwa Yuji , Okano Ken
Published: April 2011

Electric field of less than 5 V/um is enough to extract electrons from CVD diamond, whereas field of one to two orders of magnitude higher is needed to extract electrons from metal emitter tips. Diamond has various advantages as an electron emitter in addition to the low-threshold voltage, negative electron affinity (NEA), high thermal conductivity, and high chemical stability. The difficulty in clarification of electron emission mechanism is the factor preventing diamond from being used in practical Quite a few numbers of possible mechanisms have been proposed based on conventional emission current-anode voltage (I-V) characteristics, however, difficulty remained in the determination of origin for emitting electrons. In our previous study, we have succeeded in determining the origin for lightly nitrogen (N)-doped CVD diamond by using combined x-ray photoemission spectroscopy / ultraviolet photoemission spectroscopy / field emission spectroscopy (XPS/UPS/FES) system. The origin at 1.47 eV above valence band maximum (VBM) was consistent with donor level for aggregated N. The origin was at VBM for natural IIb diamond measured as a reference, indicating the emitted electrons strongly depend on the dopant In this study, the origin of emitting electrons for heavily N-doped CVD diamond was characterized by the means of combined XPS/UPS/FES. Extremely low-threshold electron emission at 0.5 V/um is still one of the lowest threshold voltages. Such a low-threshold emission may be possible if electrons are somehow injected to conduction band of diamond and emitted into vacuum through NEA surface. Hence, we strongly believe the determination of the origin for heavily N-doped CVD diamond leads to the clarification of mechanism for low-threshold electron emission from diamond. The system in which we have developed for this study consists of ultraviolet source built in an X-ray photoelectron spectrometer. The diamond sample could be negatively biased up to 4kV relative to the mesh grid for FES. Individual spectroscopy of XPS was performed prior to the combined spectroscopy to determine any possible contaminants on CVD diamond. Peaks referred to C1s and O1s of diamond were observed in addition to Gold, used in a mesh grid set above the sample. Combined spectroscopy of UPS/FES was then, conducted on the CVD diamond to identify the origin of field emitted electrons. The diamond was first illuminated by He I excitation for photoemission. NEA with the typical spectra shape for diamond was observed. After confirming stable operation of individual UPS, negative voltage was applied simultaneously for field emission. Exceeding threshold voltage, a sharp peak, which can be referred to field-emitted electrons appeared in addition to typical UPS spectra. The origin of emitting electrons as well as its dependence on the applied voltage will be discussed.
Barrier Height Difference Induced by Surface Terminations for Field Emission from P-doped Diamond
Authors: Kudo Yuki , Yamada Takatoshi , Yamaguchi Hisato , Masuzawa Tomoaki , Saito Ichitaro , Shikata Shin-ichi , Nebel Christoph E. , Okano Ken
Published: April 2011

In this paper, we measured the field emission properties of reconstructed P-doped diamond under various anode-diamond distances and compared with the oxidized surface. Voltage drops in the vacuum was estimated to be 4.95 and 26.6 V/μm for the reconstructed and the oxidized, respectively. Moreover, we calculated the barrier height ratio between each surface. Our data indicates the changes in electron affinity strongly affect on the field emission properties.
Phosphorous Doping of Microcrystalline CVD Diamond Using Modified Conditions
Authors: Haenen Ken , Lazea Andrada , Mortet Vincent , D'Haen Jan , Geithner Peter , Ristein Jürgen
Published: April 2011

Phosphorous-doping of predominantly (110) oriented polycrystalline CVD diamond films is presented. Incorporation of phosphorous into the diamond grains was accomplished by using novel microwave plasma enhanced chemical vapor deposition (MW PE CVD) growth conditions. The substitutional nature of the phosphorous atom was confirmed by applying the quasi-steady-state photocurrent technique (PC) and cathodoluminescence (CL) measurements at low temperature. Topographical information and the relation between substrate and P-doped film grain orientation was obtained with scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). The optimized growth parameters for P-doped layers on (110) oriented polycrystalline diamond differ substantially from the standard conditions reported in literature for P-doping of single crystalline (111) and (100) oriented diamond surfaces.
Life Cycle Assessment of Photovoltaics; Update of the ecoinvent Database
Authors: Jungbluth Niels , Dones Roberto , Frischknecht Rolf
Published: April 2011

Recently, the data for photovoltaics in the ecoinvent database have been updated on behalf of the European Photovoltaics Industry Association and the Swiss Federal Authority for Energy. Data have been collected in this project directly from manufacturers and were provided by other research projects. LCA studies from different authors are considered for the assessment. The information is used to elaborate a life cycle inventory from cradle to grave for the PV electricity production in 3kWp plants in the year 2005.

The inventories cover mono- and polycrystalline cells, amorphous and ribbon-silicon, CdTe and CIS thin film cells. Environmental impacts due to the infrastructure for all production stages and the effluents from wafer production are also considered. The ecoinvent database is used as background database.

Results from the LCA study are presented, comparing different types of cells and analysing also the electricity production in a range of different countries. It is also discussed how the environmental impacts of photovoltaics have been reduced over the last 15 years, using the CED indicator. The consistent and coherent LCI datasets for basic processes make it easier to perform LCA studies, and increase the credibility and acceptance of the life cycle results. The content of the PV LCI datasets is made publicly available via the website www.ecoinvent.org for ecoinvent members.
Comparative Life-cycle Analysis of Photovoltaics Based on Nano-materials: A Proposed Framework
Authors: Kim Hyung Chul , Fthenakis V. , Gualtero S. , van der Meulen R. , Kim H. C.
Published: April 2011

Life cycle analysis becomes especially important for characterizing new material forms in new energy generation technologies intended to replace or improve the current infrastructure of energy production. We propose a comparative life-cycle analysis framework for investigating the effect of introducing nanotechnology in the life cycle of new photovoltaics, which focuses on the differences between the new technologies and the ones that they may replace. The following parameters are investigated within this framework: methods of synthesizing nanoparticles, physicochemical specifications of the precursors, material utilization rates, deposition rates, energy-conversion efficiencies, and lifetime expectancy of the final product. We introduce the application of this framework in comparing nano-structured cadmium telluride and silicon films with their nano- and amorphous- structured equivalents.
A Novel High Capacity, Environmental Benign Energy Storage System: Super-iron Boride Battery
Authors: Yu Xingwen , Licht Stuart
Published: April 2011

High electrochemical capacity of alkaline boride anodes is presented. The alkaline anodes based on transition metal borides can deliver exceptionally high discharge capacity. Over 3800 mAh/g discharge capacity is obtained for the commercial available vanadium diboride (VB2), much higher than the theoretical capacity of commonly used zinc metal (820 mAh/g) alkaline anode. Coupling with the super-iron cathodes, the novel Fe6+/B2- battery chemistry generates a matched electrochemical potential to the pervasive, conventional MnO2-Zn battery, but sustains a much higher electrochemical capacity.
Wise Energy Investment Decisions–Not Just [kJ out/kJ in]
Authors: Laurin Lise
Published: April 2011

While the best energy solutions may seem obvious to the LCA community, we often see wind turbines voted down for aesthetics and policy makers leaning toward solutions that show poor return, kilojoule per kilojoule. If we are to move forward with wise energy solutions, we will need to broaden our perspective to include the social impacts that influence policy-makers and communities, creating a decision-system that encompasses both social and environmental impacts.

Starting with LCA and Total Cost Assessment, a case study of a biodiesel facility in Vermont begins to incorporate social goals with reduced environmental impacts. We'll then look at other energy systems and how these decision-making tools might be used to bring policy makers, environmentalists, and communities together making wise energy choices for our future.
METAL HYDRIDE ALLOYS FOR ELECTROCHEMICAL ENERGY SOURCE APPLICATIONS
Authors: Bliznakov Stoyan Todorov , Dimitrov Nikolay G , Spassov Tony , Popov Alexander
Published: April 2011

High-capacity conventional and advanced multicomponent metal hydride alloys were synthesized in this work by two different methods. A set of AB5–type intermetallic compounds, with different Al content, were produced by high-frequency vacuum induction melting method, while AB, A2B and mixed (AB5+Mg)-types composite nanocrystalline-amorphous alloys were obtained mechanochemically by high-energy ball milling in a planetary type mill. The alloys were characterized physically by XRD, SEM and thermodynamically by van't Hoff's plots derived from experimentally obtained PCT isotherms at various temperatures. Different optimized techniques for model electrode preparation from selected metal hydride alloys were also applied. The electrodes were charged-discharged electrochemically in concentrated alkaline solution. In this paper we compare the values for the electrochemical maximum capacity and cycle-life performance of the electrodes prepared by the investigated types of alloys.
Effect of Thermal Treatments on the Transduction Behaviors of Conductometric Hydrogen Gas Sensors Integrated with HCl-Doped Polyaniline Nanofibers
Authors: Wang Pen-Cheng , Dan Yaping , Somers Luke A. , MacDiarmid Alan G. , Johnson A.T. Charlie
Published: April 2011

We present the effect of thermal treatments on the transduction behaviors of HCl-doped polyaniline (PANI) nanofibers integrated in conductometric devices upon exposure to 1% H2 (carried by N2). After drying in N2 at 25ºC for 12 hours, devices showed a ∼10% decrease in electrical resistance upon exposure to 1% H2. However, devices subject to 12-hour drying in N2 at 25ºC followed by further thermal treatments in N2 at 100ºC, 164ºC or 200ºC for 30 minutes showed different transduction behaviors. Specifically, devices subject to thermal treatments at 100ºC and 164ºC showed a decrease in electrical resistance by ∼7% and <0.5%, respectively. More interestingly, the device subject to thermal treatment at 200ºC showed a transduction behavior with opposite polarity, i.e. a ∼5% increase in electrical resistance upon exposure to 1% H2. SEM, FTIR and TGA were employed to investigate the effect of thermal treatments on the morphology and chemical characteristics of HCl-doped polyaniline nanofibers. The results indicated that the change in the devices' interesting transduction behaviors might be related to the thermal treatment effects on the HCl-doped PANI nanofibers in (i) removal of adsorbed water, and (ii) crosslinking and/or degradation of polymer backbones.
SWNTs Bundle Dispersion Study and Analysis of its Potential as a Hydrogen Tank
Authors: Tange Kyoichi , Hirose Katsuhiko , Noda katsutoshi , Mohtadi Rana , Kojima Yoshitsugu
Published: April 2011

High pressure physic-sorption hydrogen tank using high purity and high surface area SWNTs is considered to be one of the most promising hydrogen tank systems
From Bytes to Ingots: Expedient Design of Structural Materials for Advanced Nuclear Energy Systems
Authors: Zinkle Steven
Published: April 2011

Development of structural materials is historically a long and costly process, particularly for nuclear energy applications due to the long proof testing period to validate the performance of the material in the hostile irradiation environment. Utilization of recently developed materials science tools including computational thermodynamics and multiscale radiation damage computational models in conjunction with rapid science-guided experimental validation (nonirradiation and irradiation environments) may offer the potential for a transformational reduction in the time period to develop and qualify structural materials for advanced nuclear energy systems. Several examples of rapid development of high-performance structural materials will be given, with a focus on austenitic and ferritic/martensitic steels (less than two years from project initiation to commercial production of multi-ton prototypic heats). In many cases, the key for development of improved mechanical properties and superior radiation stability is the presence of a uniform high-density dispersion of highly stable nanoscale particles. This research was sponsored in part by the Office of Fusion Energy Sciences, U.S. Department of Energy under contract DE-AC05-00OR22725 with UT-Battelle, LLC.
Characterization of Point Defect Generation, Migration and Coalescence in Irradiated SiC by Atomistic Simulation
Authors: Farrell David , Bernstein Noam , Liu Wing Kam
Published: April 2011

Renewed interest in nuclear power in the United States has prompted investigations into new reactor designs, resulting in a need to gain a greater understanding of the properties of the materials which are proposed for use in next generation nuclear reactors. This presentation will focus on preliminary results of large-scale empirical potential atomistic studies into the generation of point defect clusters in 3C SiC by particle irradiation and the evolution from point defect clusters to ‘voids’ on the atomic scale. Our working definition of ‘void’ will be explained in the context of small length-scale simulations. The determination of interstitial and vacancy diffusivities for the empirical potential employed and its impact on defect coalescence will be discussed. The characterization of initial damage states for given irradiation conditions will be presented and compared to previous work on ceramics and ceramic-composites.
Influence of Phase Stability on Radiation Damage Properties: Plutonium-Gallium Alloys
Authors: Valone Steve , Baskes Michael I. , Uberuaga Blas P. , Martin Richard L. , Kubota Alison , Wolfer Wilhelm G.
Published: April 2011

Modeling cascade and fission damage evolution of actinide materials of all kinds is essential for understanding their aging characteristics. As an example of how exotic some of the damage evolution behavior can be, plutonium-gallium (Pu-Ga) alloys in the δ-phase (fcc lattices) are explored. Aging emanates from the wide variety of spontaneous decay and fission products that, in the case of the Pu, are such species as helium (He) and uranium, among others, as well as interstitials, and vacancies. To aid in our understanding, the modified embedded atom method (MEAM) formalism is applied to the Pu-Ga-He system. The behavior of defects in the fcc (δ) phase of Pu-based materials is strongly influenced by the metastability of this phase. The influence of this metastability on minimum displacement threshold energy, point defect characteristics and He bubbles is delineated. The roles of short-range ordering and transformations of voids into stacking fault tetrahedra in the aging process are also examined.
Effects of Hydrogen Absorption on the Mechanical Properties of Zr-Nb Alloys
Authors: Nishioka Shunichiro , Ito Masato , Muta Hiroaki , Uno Masayoshi , Yamanaka Shinsuke
Published: April 2011

Young's moduli of hydrogenated Zr-Nb alloys were evaluated by using a multiple elastometer in the temperature range from room temperature to 773 K, based on the cantilever characteristic vibration technique. The decreasing rate of Young's modulus against the temperature was independent on the additive amount of Nb. The Young's modulus for the hydrogen solid solution of Zr-Nb alloys decreased and that those for the alloys with partially precipitated hydride slightly changed with increasing hydrogen content in both of Zr-1.0Nb and Zr-2.5Nb. The decreasing rates with hydrogen content of hydrogen solid solution of Zr-Nb alloys were almost same as that of Zr hydrogen solid solution. This result was considered because all specimens largely consisted of α-zirconium in which the solute hydrogen was found to decrease the Young's modulus.
Thermophysical Properties of PuO2 and AmO2 Solid Solutions Simulated by Molecular Dynamics
Authors: Seetawan Tosawat , Khuangthip Thaweewat , Amornkitbamrung Vittaya , Kurosaki Ken , Adachi Jun , Katayama Masahito , Charoenphakdee Anek , Yamanaka Shinsuke
Published: April 2011

PuO2 and AmO2 solid solutions: (Pu, Am)O2 are one of the candidates of fuels in a sub-critical accelerator-driven system (ADS). To understand the fuel performance, the thermophysical properties such as thermal conductivity and heat capacity are quite important. However, it is very hard to experimentally determine the physical properties of plutonium as well as americium compounds due to their handling-difficulties. Molecular dynamics (MD) would be a specific method to describe the physical properties of such materials. In the present study, we have investigated thermophysical properties of PuO2, AmO2, and their solid solutions in the temperature range from 300 to 2,500 K. The lattice parameter, compressibility, heat capacity, linear thermal expansion coefficient, and thermal conductivity were evaluated. A Morse-type potential function added to the Busing-Ida type potential was employed as the potential for interatomic interactions. The calculated lattice parameters of (Pu, Am)O2 obeyed Vegard's law, and the values increased with temperature. The heat capacities of (Pu, Am)O2 were similar in any compositions. The thermal conductivities of (Pu, Am)O2 were lower than those of PuO2 and AmO2, indicating that a point-defect scattering effect of phonons could be realized in the MD calculations.
Indentation study of titanium, zirconium, and hafnium hydrides
Authors: Ito Masato , Nishioka Shunichiro , Muta Hiroaki , Kurosaki Ken , Uno Masayoshi , Yamanaka Shinsuke
Published: April 2011

Mechanical properties of titanium, zirconium, and hafnium hydrides were evaluated by indentation tests in the present study. Single-phase bulk specimens of titanium, zirconium, and hafnium hydrides with a fluorite type structure were produced using a Sieverts' apparatus. The indentation hardness values of titanium and hafnium hydrides were lower than those of the pure metals and drastically decreased with increasing hydrogen content. The hardness of zirconium hydride was higher than that of pure zirconium and slightly depended on hydrogen content. The hardness of the hydrides decreased with increasing maximum indentation load, which has been referred to as indentation size effect. The dependences of hardness on the indentation depth for the hydrides were found to obey the Nix–Gao model. The indentation size effects for the hydrides were significantly smaller than those for the pure metals.
Synthesis and Thermoelectric Properties of Lead Chalcogenide Nanocomposites
Authors: Martin Joshua , Stefanoski Stevce , Wang Li , Chen Lidong , Nolas George S.
Published: April 2011

Doped lead telluride dimensional nanocomposites were prepared by densifying nanocrystals synthesized employing an alkaline aqueous solution-phase reaction. The nanocrystal synthesis procedure resulted in high product yields of over 2 g per batch. These nanocrystals were then subjected to Spark Plasma Sintering (SPS) for densification. Transport properties were evaluated through temperature dependent resistivity, Hall, Seebeck coefficient, and thermal conductivity measurements. The results for these lead telluride nanocomposites were compared to bulk polycrystalline lead tellurides with similar carrier concentrations.
In-situ TEM Study of Bismuth Nanostructures
Authors: Jia Xiaoting , Berube Vincent , Chen Shuo , Poudel Bed , Hyungbin Son , Kong Jing , Shao-Horn Yang , Zhifeng Ren , Chen Gang , Dresselhaus Mildred S
Published: April 2011

Nanostructured thermoelectric materials have attracted lots of interest in recent years, due to their enhanced performance determined by their thermoelectric dimensionless figure of merit. However, because of equipment limitations, not much work has been done on combining simultaneous transport measurements and structural characterization on individual nanostructured thermoelectric materials. With an integrated TEM-STM system, we studied the structural behavior and electrical properties of bismuth (Bi) nanobelts and nanoparticles. Results showed that clean Bi nanostructures free of oxides can be produced by in-situ high temperature electro-migration and Joule annealing processes occurring within the electron microscope. Preliminary electrical measurements indicate a conductivity of two orders of magnitude lower for Bi nanoparticles than that for bulk Bi. Such in-situ studies are highly advantageous for studying the semimetal-semiconductor transition and how this transition could enhance thermoelectric properties.
Ternary Skutterudites: Anion Ordering and Thermoelectric Properties
Authors: Vaqueiro Paz , Sobany Gerard G.
Published: April 2011

The ternary skutterudites AB1.5Q1.5(A = Co, Rh, Ir, B =Ge, Sn and Q = S, Te) have been synthesized and structurally characterised. Powder diffraction data are consistent with the presence of anion ordering, which results in a lowering of the symmetry from cubic to rhombohedral. The ordered skutterudite structure contains rhomboidal four-membered B2Q2rings, instead of the homonuclear rectangular rings found in binary skutterudites. The electrical transport properties of the AB1.5Q1.5phases are consistent with semiconducting behaviour, and large values of the Seebeck coefficient have been observed for several of these materials. While their large electrical resistivities might make these materials unsuitable for thermoelectric applications unless significant improvements can be achieved by doping, these materials also exhibit significantly lower thermal conductivities than their binary counterparts.
Enhanced Thermoelectric Figure of Merit in BaxYbyCo4Sb12 Skutterudites
Authors: Uher Ctirad , Shi Xun , Kong Huijun
Published: April 2011

We report on the development of an efficient n-type skutterudite based on the double-filled structure of CoSb3. The chosen filler species Ba and Yb have a large phonon contrast and this combination is very effective in lowering the lattice thermal conductivity. The highest figure of merit in excess of 1.3 is obtained near 800K and the figure of merit greater than unity persists down to temperatures of about 550K. The compounds are synthesized with high purity Co (99.998%) and Sb (99.9999%). In order to reduce the cost of the materials, we have also prepared filled skutterudites of similar composition but using less pure Co (99.8%) and Sb (99.999%). The figure of merit of these lower purity compounds reaches ZT = 1 at 800K with the materials' cost dramatically reduced.
Zintl Phase as Thermoelectric Materials: Synthesis, Structure and Properties of Yb5Al2Sb6
Authors: Todorov Iliya , Chung Duck-Young , Kanatzidis Mercouri
Published: April 2011

We present the synthesis, crystal structure, spectroscopic properties, and electronic structure of a new member of the Zintl family, Yb5Al2Sb6. The compound crystallizes in the Ba5Al2Bi6 structure type. A preliminary assessment of its thermoelectric properties including electrical conductivity, thermopower, and thermal conductivity are reported. Moreover, investigations of solid solutions of this phase, doping effects and chemical modifications will be presented. The room temperature conductivity, thermopower and thermal conductivity of Yb5Al2Sb6/0.5Ge were 1100 S/cm, 20 μV/K, and 3.8 W/m.K, respectively.
Thermoelectric Properties of La-doped BaSi2 and (Ba,Sr)Si2 Solid Solutions
Authors: Hashimoto Kohsuke , Kurosaki Ken , Muta Hiroaki , Yamanaka Shinsuke
Published: April 2011

We studied the thermoelectric properties of BaSi2 and SrSi2. The polycrystalline samples were prepared by spark plasma sintering (SPS). The electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) were measured above room temperature. The maximum values of the dimensionless figure of merit (ZT) were 0.01 at 954 K for BaSi2 and 0.09 at 417 K for SrSi2. We tried to enhance the ZT values of BaSi2 and SrSi2 by prepareing and characterizing La-doped BaSi2 and (Ba,Sr)Si2 solid solution.
Thallium-Free Thermoelectric Materials with Extremely Low Thermal Conductivity
Authors: Yamanaka Shinsuke , Kurosaki Ken , Charoenphakdee Anek , Mastumoto Hideaki , Muta Hiroaki
Published: April 2011

With the goal of developing high-performance bulk thermoelectric materials, we have characterized ternary silver thallium tellurides. The ternary silver thallium tellurides exhibit extremely low thermal conductivity (<0.5 Wm−1K−1) and consequently their thermoelectric performance is excellent. Although the extremely low thermal conductivity materials, as typified by the ternary silver thallium tellurides, would be a new class of next-generation thermoelectric materials, thallium compounds are unsuitable for practical application because of their toxicity. Against such a background, we are currently exploring thallium-free thermoelectric materials with extremely low thermal conductivity. In this paper, we will briefly summarize the thermoelectric properties of ternary thallium tellurides obtained in our group. Further experiments aimed at improving the ZT of these materials will be presented. Finally, we will propose two candidates: Ag8GeTe6 and Ga2Te3 as thallium-free low thermal conductivity materials.
Thermoelectric Properties of the Nanostructured NaPb18-xSnxMTe20 (M=Sb, Bi) Materials
Authors: Gueguen Aurelie , Poudeu Poudeu Pierre Ferdinand , Pcionek Robert , Kong Huijun , Uher Ctirad , Kanatzidis Mercouri G.
Published: April 2011

The thermoelectric properties of materials with compositions NaPb18-xSnxMTe20 (M=Sb, Bi, x=0, 3, 5, 9, 13, 16 and 18) were investigated in the temperature range 300-670K. All compositions exhibited p-type behavior over the measured temperature range. Electronic properties and transport were tuned through the manipulation of the Pb/Sn ratio. Increasing the Sn fraction results in an increase in electrical conductivity and a decrease in thermopower. The compositions NaPb13Sn5SbTe20 and NaPb9Sn9SbTe20 show a lattice thermal conductivity of ∼1 W/m/K at room temperature.
Quantum Size Effect of 2DEG Confined Within BaTiO3/SrTiO3:Nb Superlattices
Authors: Nakanishi Yuki , Ohta Hiromichi , Mizoguchi Teruyasu , Ikuhara Yuichi , Koumoto Kunihito
Published: April 2011

Very recently, we have found that the high density 2DEG (ne ∼1021 cm−3), which is confined within a unit cell layer thickness of SrTiO3, exhibits unusually large Seebeck coefficient (S2DEG/Sbulk ∼5)[1]. In the optimum, extremely high ZT2DEG of ∼2.4 can be obtained at room temperature, while the effective ZTeff. was only ∼0.24 because 9 unit cells of electrically insulating SrTiO3 layers were used to fabricate the 2DEG structure. Thus, high ZTeff can be realized if the insulating layer thickness is reduced significantly. We selected BaTiO3∼SrTiO3:Nb superlattice to reduce insulating layer thickness because dielectric constant of BaTiO3 is one order of magnitude large (∼3,000) as compared to that of SrTiO3 (∼300). We expected that the conduction electrons can be confined much strongly in the SrTiO3:Nb layer by sandwiching between highly dielectric BaTiO3 layers. As a result, we clarified that the critical BaTiO3 layer thickness is 1.2 nm, significantly small as compared to SrTiO3 layer (4 nm). The BaTiO3/SrTiO3:Nb superlattice films were fabricated by a pulsed laser deposition (PLD) method on (001)-face of LaAlO3 single crystal substrate at 900°C. During the film growth, we monitored RHEED intensity oscillation to control layer thickness precisely. Out-of-plane high-resolution X-ray diffraction measurements and cross sectional HAADF-STEM observations revealed that the resultant films were high quality BaTiO3/SrTiO3:Nb superlattice. Hall mobility of the SrTiO3:Nb layer was 0.4 cm2·V−1·s−1, while that of superlattice decreased gradually with increasing BaTiO3 layer thickness most likely due to that intra layer diffusion of Ba2+ ion occurred between BaTiO3 and SrTiO3:Nb layers[2], which was clearly observed by the EELS mapping. Seebeck coefficient |S|300K of SrTiO3:Nb layer was 57 μV·K−1, which corresponds carrier concentration ne of 5×1021 cm−3. The |S|300K value became large with decreasing the SrTiO3:Nb layer thickness (dSrTiO3:Nb) and it reached 305 μV·K−1, which is approximately 5 times larger than that of SrTiO3:Nb bulk. The slope of log |S|- log dSrTiO3:Nb plots was 1/2, suggesting that quantum size effect occurred. Critical BaTiO3 layer thickness for the quantum confinement of the electrons was 1.2 nm (3 unit cells of BaTiO3), which is significantly small as compared to SrTiO3 (4 nm). Thus, BaTiO3/SrTiO3:Nb superlattice would be a promising candidate to realize high ZTeff.
Characterization of Thin-film Thermoelectric Micro-modules using Transient Harman ZT Measurement and Near-IR Thermoreflectance
Authors: Singh Rajeev , Christofferson James , Bian Zhixi , Nurnus Joachim , Schubert Axel , Shakouri Ali
Published: April 2011

We characterize several thin film thermoelectric micro-modules composed of 20 µm-thick elements and designed for cooling applications to identify factors that may limit device performance. Thermoelectric figure-of-merit measurements using the transient Harman technique are compared with maximum cooling data under no heat load. Correlation between the two measurements depending on the location of the parasitic joule heating in the module is analyzed. Near-infrared thermoreflectance is used to examine temperature non-uniformity in the module. The temperature distribution on the metal contacts due to the Peltier and Joule effects is obtained non-destructively through the silicon substrate of an active module.
Segmented Power Generator Modules of Bi2Te3 and ErAs:InGaAlAs Embedded with ErAs Nanoparticles
Authors: Zeng Gehong , Bahk Je-Hyeong , Bowers John E. , Lu Hong , Zide Joshua M. O. , Gossard Arthur C. , Singh Rajeev , Bian Zhixi , Shakouri Ali , Singer Suzanne L. , Kim Woochul , Majumdar Arun
Published: April 2011

We report the fabrication and characterization of segmented element power generator modules of 254 thermoelectric elements. The element is 1 mm × 1 mm in area, which consists of 300 μm thickness Bi2Te3 and 50 μm thickness ErAs:(InGaAs)1-x(InAlAs)x, so that each segment can work at different temperature ranges. Erbium arsenide metallic nanoparticles are incorporated to create scattering centers for middle and long wavelength phonons, provide charge carriers, and form local Schottky barriers for electron filtering. The thermoelectric properties of ErAs:InGaAlAs were characterized by variable temperature measurements of thermal conductivity, electrical conductivity and Seebeck coefficient from 300 K to 600 K. Generator modules of Bi2Te3 and ErAs:InGaAlAs segmented elements were fabricated and an output power over 5.5 W was measured. The performance of the thermoelectric generator modules can further be improved by improving the thermoelectric properties of the element material, and reducing the electrical and thermal parasitic losses.
Simultaneous Cr(VI) Reduction and Naphthalene Oxidation in Aqueous Solutions by UV/TiO2
Authors: Guitierrez Ricardo , Flores Sergio o , Rios Omar , Valenzuela Miguel
Published: April 2011

The photocatalytic reduction of Cr (VI) and oxidation of naphthalene using UV light and TiO2 were investigated with variations in the pH and Cr (VI)/naphthalene ratio. The photochemical reduction of Cr (VI) single system was not observed, whereas the photochemical oxidation of naphthalene was significantly high. However, the reduction reaction rates of Cr (VI) and oxidation of naphthalene were improved in the system UV/TiO2. The removal of Cr (VI) decreased dramatically with increasing pH, in contrast, the naphthalene removal was not influenced by the pH. The presence of naphthalene functioned as a hole scavenger enhancing the photocatalytic reduction of Cr (VI) by the photogenerated electrons, while the removal of naphthalene was decreasing at increasing Cr (VI) content.
Collaboration between the Exploratorium Museum (San Francisco) and the University of Chicago MRSEC in Educational Outreach Programs
Authors: Sheu Eileen , Jaeger Heinrich , Nagel Sidney , Kluger-Bell Barry , Lani Shawn , Sowers Charles
Published: April 2011

Science centers and museums have long been at the forefront of communicating the wonder of science to the general public and the K-12 school community. Interactions between the Exploratorium Museum (San Francisco, CA) and the University of Chicago MRSEC are described in this paper. The Exploratorium-organized NEO program—part of the NSF-sponsored NISE network—has greatly influenced the Univ. of Chicago's approach to its materials science course for teachers and helped them incorporate inquiry more deliberately into their after-school science clubs. Also, Exhibit Developers at the Exploratorium collaborate with scientists at the Univ. of Chicago to design exhibits that explain contemporary cutting-edge research in materials. These exhibits emphasize the wonder and beauty of common phenomena that one rarely stops to notice but which leads to deep scientific inquiry.
The Nanoscience and Engineering High School Research Internship program at the University of Alabama
Authors: Nikles David E. , Thompson Gregory B.
Published: April 2011

The Center for Materials for Information Technology provides a ten-week summer research experience in nanoscience and engineering for high school students. The students were between their junior and senior year or their sophomore and junior year and were interested in a career in scientific research. Each student had their own research project within the general theme of metal alloy nanoparticles. They were trained in safe laboratory practice and could prepare their own particles independently. Each used x-ray diffraction and SEM EDX to characterize the structure of their nanoparticles. They also identified potential applications for their particles such as magnetic recording, fuel cell catalysis and cancer therapy. Many of the students accomplished enough research to submit competitive entries to regional and national high school science fairs. Two were semi-finalists in the Siemens-Westinghouse Competition. Another won the West Alabama Science Fair and competed in the Intel International Science Fair. This program provided the high school students with a vision for the breadth and excitement of doing basic research in materials science.
Getting Students Interested in Material Science and Engineering Through A Realistic Nanotechnology Modeling Problem
Authors: Moore Tamara J.
Published: April 2011

Attracting students to engineering is a challenge. In addition, ABET requires that engineering graduates be able to work on multi-disciplinary teams and apply mathematics and science when solving engineering problems. One manner of integrating teamwork and engineering contexts in a first-year foundation engineering course is through the use of Model-Eliciting Activities (MEAs) - realistic, client-driven problems based on the models and modeling theoretical framework. A Model-Eliciting Activity (MEA) is a real-world client-driven problem. The solution of an MEA requires the use of one or more mathematical or engineering concepts that are unspecified by the problem - students must make new sense of their existing knowledge and understandings to formulate a generalizable mathematical model that can be used by the client to solve the given and similar problems. An MEA creates an environment in which skills beyond mathematical abilities are valued because the focus is not on the use of prescribed equations and algorithms but on the use of a broader spectrum of skills required for effective engineering problem-solving. Carefully constructed MEAs can begin to prepare students to communicate and work effectively in teams; to adopt and adapt conceptual tools; to construct, describe, and explain complex systems; and to cope with complex systems. MEAs provide a learning environment that is tailored to a more diverse population than typical engineering course experiences as they allow students with different backgrounds and values to emerge as talented, and that adapting these types of activities to engineering courses has the potential to go beyond “filling the gaps” to “opening doors” to women and underrepresented populations in engineering. Further, MEAs provide evidence of student development in regards to ABET standards. Through NSF-funded grants, multiple MEAs have been developed and implemented with a MSE-flavored nanotechnology theme. This paper and presentation will focus on the content, implementation, and student results of these MEAs.
Variability in Copper and Bronze Casting Technology as Seen at Bronze Age Godin Tepe, Iran
Authors: Frame Lesley , Vandiver Pamela B.
Published: April 2011

Godin Tepe lies along the “High Road” leading from the Mesopotamian lowlands to the northern Iranian Plateau and beyond. This site acted as a center for the exchange of goods, transmission of ideas, and spread of technology; therefore the technology and manufacturing methods represented by the artifacts at this site provide information regarding the technology in use across the Iranian Plateau. Materials analyzed from Godin Tepe include crucibles, furnace and tuyere fragments, ore, and metal artifacts dating to the early third through late second millennium B.C.E. The production materials were concentrated in only a few locations throughout the site, and they are indicative of small scale production. SEM and microprobe analyses have allowed the determination of cooling rates and temperatures attained during smelting and casting operations in antiquity. In addition, the analysis of approximately 60 metal artifacts (out of the two-hundred plus that were excavated) have contributed greatly to understanding the variability in manufacture methods present during this time period. The results of this investigation support two significant conclusions. First, the measurement and evaluation of secondary dendrite arm spacing of cast artifacts and crucible prills provides insight to the processes and cooling methods employed by ancient craftsmen. Second, the wide range in manufacturing methods shown by the microstructures of non-utilitarian artifacts, offers strong evidence for the presence of multiple producers who copied styles and typology, but not technological methods from their contemporary craftsmen.
Reassessing Bronze Age Manufacturing Technologies at Nuzi
Authors: Shortland Andrew , Eremin Katherine , Kirk Susanna , Armstrong James
Published: April 2011

The Hurrian city of Nuzi, in modern Iraq, was an important site during the Mesopotamian Bronze Age. Excavations in the late 20s and early 30s yielded a large and important assemblage of glass and other vitreous materials and smaller but significant assemblages of metals and ceramics. Although the vitreous materials have been widely studied in the past, the other assemblages have received little attention. However a recent study of some metal artifacts indicated the presence of brass and dirty copper rather than the expected bronze. This study was, however, limited to a few objects and the proportions of the different alloys was not investigated. Recent analytical studies on the glass beads have highlighted compositional differences between Egyptian and Mesopotamian glass and attempted to link these to the raw materials used. The lack of significant tin or zinc in glasses colored with copper is interesting given the presence of brass and the apparent scarcity of bronze in the copper alloys. The current study involves reassessment of the entire assemblage, concentrating initially on the vitreous materials, glazes and metals. Variations in preservation across the site and within individual buildings are currently being examined. Full characterization of the assemblages will allow relationships between different manufacturing technologies and the raw materials needed to be investigated.
Theory of Large-Scale Plastic Deformation in Amorphous Materials: A Progress Report
Authors: Langer James
Published: April 2011

The goal of recent shear-transformation-zone (STZ) theories has been to construct a phenomenological description of amorphous plasticity that is based on physical principles and molecular models, and yet is simple enough to be useful in predicting the performance of real materials. In reporting progress toward this goal, I focus on the dynamic role played by the effective disorder temperature (a generalization of the free-volume) in controlling relaxation rates and predicting shear-banding instabilities.
AN ANALYSIS OF THERMOPHYSICAL AND MECHANICAL PROPERTIES OF GLASS-FORMING ALLOYS
Authors: Battezzati Livio , Baldissin Daniele , Baricco Marcello , Baser Tanya Aycan , Firrao Donato , Matteis Paolo , Mortarino Giovanni M.
Published: April 2011

Metallic glass-forming liquids and glasses are ranked using thermophysical properties (glass transition, excess entropy, fragility indexes). The relationships between mechanical properties and some of the above quantities are discussed to get insight into the mechanism of shear band propagation during mechanical failure when, following up a shear offset event, a local temperature rise occurs. The mechanism is supported by evaluating the energy content of the shear band, as well as finite element modelling of temperature profiles around it.
Structural evaluation in Zr15Al5Ni57Y23bulk metallic glass under high pressure
Authors: Li Gong , Gao Yunpeng , Xu Tao , Jing Qin , Liu Jing , Liu Riping
Published: April 2011

The compression behavior of Zr15Al5Ni57Y23bulk metallic glass is investigated at room temperature usingin-situhigh pressure energy dispersive X-ray diffraction with a synchrotron radiation source. The structural information of the atomic configuration about Zr15Al5Ni57Y23bulk amorphous alloy such as coordination number (CN), neighbor atomic distance is gained by Fourier transformation under different pressure. The investigation shows that the structure of Zr15Al5Ni57Y23bulk metallic glass is stable under the pressure ranging from zero to 31.7 GPa, but the degree of short-range order changes by the pressure altering the second and the third nearest neighbor local atomic configuration of the amorphous alloy.