bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Fabrication of ZnO Whiskers Bridging Between Micron-gap Electrodes in Aqueous Solution for Highly Gas Sensing
Authors: Reiko Hattori , KAMETANI Keisuke , IMAMOTO Hiroshi , FUJITA Shizuo
Published: April 2011

A simple but convenient method for fabricating ZnO micro-sized structure selectively and artificially between two micron-gap electrodes was proposed and investigated. The technique is based on electrolytic deposition in aqueous solution of zinc nitrate or zinc acetate, which selectively occurs between the electrodes being enhanced by electric field. The deposition characteristics were investigated in terms of the deposition conditions, and under the optimized condition ZnO micro-sized structure was obtained with bridging between the electrodes. The gas sensing characteristics of the structure was investigated by exposing to a 500 ppm H2 gas, resulting in 23% variation of the resistance at room temperature. The device dimensions can be downsized to nanometer scale by applying nano-gap electrodes, and therefore this technique is promising for fabrication of highly functional nano-sized sensors at low cost, contributing to mass applications.
A Theoretical Study of Ultra-Thin Films with the Wurtzite and Zinc Blende Structures
Authors: Claeyssens Frederik , Freeman Colin L. , Harding John H. , Allan Neil L.
Published: April 2011

Results of periodic ab initio density functional theory calculations on thin films of (i) wurtzite ZnO (hexagonal) which terminate with the non-polar (1010) surface, and with the polar (0001) and (0001) surfaces (ii) zinc blende (cubic) ZnO which terminate with the non-polar (110) and with the polar (111) surfaces. Thin (less than18 layer) films of wurtzite ZnO which terminate with the polar (0001) and (0001) surfaces are found to be higher in energy than corresponding films in which these polar surfaces flatten out forming a new planar ‘graphitic’-like structure in which the Zn and O atoms are coplanar and the dipole is removed. This is the lowest energy surface for ultra-thin films. For zinc-blende ZnO a graphitic-type solution, but with a different stacking of ZnO layers, is also comparable to energy to the non-polar (110) and polar (111) solutions. Consequences for crystal growth and the stabilization of thin films and nanostructures are discussed.
InGaN Layers Grown on Al2O3/ZnO Substrates Prepared by Atomic Layer Deposition
Authors: Li Nola , Wang Shen-Jie , Nause Jeff , Valencia Adriana , Summers Christopher , Ferguson Ian
Published: April 2011

Atomic layer deposition (ALD) of Al2O3 is used as a passivation layer on ZnO substrates before nitride growth by metalorganic chemical vapor deposition (MOCVD). This layer is being used to prevent Zn diffusion from the substrate, protect the ZnO surface from H2 back etching, and promote high quality nitride growth. ALD-Al2O3 films were grown at 100°C and then annealed in a furnace at various times at 1100°C for crystallization of the passivation layer. XRD results showed both Al2O3 and ZnAl2O4 phases at different intensities for 50 and 20nm ALD-AlM2O3 films. In addition, the InGaN layer has been successfully grown on the passivated ZnO substrate. Findings show that a short annealing time for the ALD-Al2O3 layer will be optimal for InGaN growth.
Applications of First Principles Theory to Inorganic Radiation Detection Materials
Authors: Singh David Joseph , Takenaka H. , Jellison G. E. , Boatner Lynn A.
Published: April 2011

Applications of first principles methods to understand properties of several known and potential scintillators for radiation detection are described. These include results for rare earth and Pb-based phosphates, rare-earth trihalides, ZnO, perovskites and tungstates.
Spontaneous increase of electric conductivity of nanostructure dielectrics
Authors: Lorikyan Martiros
Published: April 2011

In this report, phenomenon of acquisition of spontaneous electron conductivity (SEC) of porous CsBr is investigated and compared with that for porous CsI at the same experimental conditions.
Effects of Gamma Irradiation on Optical Properties of Colloidal Nanocrystals
Authors: Withers Nathan J , Sankar Krishnaprasad , Akins Brian A. , Memon Tosifa A. , Gu Jiangjiang , Gu Tingyi , Bowers Shin T. , Greenberg Melisa R. , Smolyakov Gennady A. , Busch Robert D. , Osinski Marek
Published: April 2011

The effects of 137Cs gamma irradiation on photoluminescence properties, such as spectra, light output, and lifetime, of several types of colloidal nanocrystals have been investigated. Irradiation-induced damage testing was performed on CdSe/ZnS, LaF3:Eu, LaF3:Ce, ZnO, and PbI2 nanocrystals synthesized on a Schlenk line using appropriate solvents and precursors. Optical degradation of the nanocrystals was evaluated based on the measured dependence of their photoluminescence intensity on the irradiation dose. Radiation hardness varies significantly between various nanocrystalline material systems.
Diamond Nanoparticles as Photoluminescent Nanoprobes for Biology
Authors: Faklaris Orestis , Elli Alexandra , Joshi Vandana , Sauvage Thierry , Boudou Jean-Paul , Roch Jean-François , Curmi Patrick , Treussart François
Published: April 2011

The present work reports our attempt in developing diamond nanoparticles with size<50 nm as photoluminescent nanoprobes for biological applications like biomolecule tracking in living cell.
Single Crystal CVD Diamond Detectors: Position and Temporal Response Measurements using a Synchrotron Microbeam Probe
Authors: Morse John , Salomé Murielle , Berdermann Eleni , Pomorski Michal , Grant James , O'Shea Val , Ilinski Petr
Published: April 2011

Ultrapure, homoeptaxially grown CVD single crystal diamond is a material with great potential for the fabrication of ionizing radiation detectors for high energy, heavy ion physics, and realtime dosimetry for radiotherapy. Only diamond has suitable transmission properties and can offer the required radiation hardness for synchrotron X-ray beam monitoring applications. We report on experiments made using a synchrotron X-ray microbeam probe to investigate the performance of single crystal diamonds operated as position sensitive, solid state ‘ionization chambers’. We show that for a wide range of electric fields >0.3Vµm−1, suitably prepared devices give excellent spatial response uniformity and time stability. With an applied field of 2Vµm−1 complete charge collection times are ∼1nsec for a diamond plate thickness of 100µm. Position sensitivity was obtained for an X-ray beam incident on the isolation gap between adjacent electrodes of a quadrant device: here, a crossover response region that results from charge carrier diffusion extends over ∼20µm. Using GHz bandwidth signal processing electronics, the signal charge collection process was measured with spatial and temporal resolutions of 1µm and <50ps.
Single Crystal CVD Diamond Growth for Detection Device Fabrication
Authors: Nicolas Tranchant , Tromson Dominique , Bergonzo Philippe , Nesladek Milos
Published: April 2011

Single crystal (SC) CVD diamond is known to exhibit superior electronic properties than polycrystalline ones for detection applications. In our study, tested samples were grown using CVD in an ASTEX type reactor, at various microwave powers and keeping all other parameters constant. The crystalline quality and purity of the samples were investigated using Raman spectroscopy and birefringence microscopy measurements.

The diamonds layers were chemically cleaned and oxidized, towards ionization chamber fabrication using Ni and Au contacts for rectifying properties. The devices electronics and detection properties were then evaluated: leakage currents were probed from I(V) measurements and the contacts behavior were tested under 60Co source at various dose rates. Time Of Flight (TOF) and Charge Collection Efficiency (CCE) measurements were evaluated under an 241Am alpha source and enabled the measurement of the mobility, carrier diffusion lengths and lifetime as a function of the growth parameters. Moreover the response under a UV pulsed flash lamp was probed in order to appreciate the CCE as a function of the repetition rate. The measurements demonstrated the importance of the power density during growth on the detection properties.
STM Characterization of Low Dimensional Surface Electronic Properties of Undoped Diamond in Buffer Solutions
Authors: Yang Nianjun , Uetsuka Hiroshi , Yamada Takatoshi , Nebel Christoph E.
Published: April 2011

Diamond is a promising semiconductor which shows some unique surface electronic features if grown optimized with low bulk and surface defect densities. The appearance of a highly conducting surface layer if immersed into electrolyte solution is maybe the most striking feature. Scanning tunneling microscopy experiments on diamond in electrolyte solutions are applied to determine the electronic properties governing these transition. These experiments reveal the formation of unoccupied quantized electronic states in the valence band close to the surface. A two-dimensional density of state distribution with three levels from light-, heavy-, and split-off-band holes is detected. Removal of the electrolyte causes a reversible transition into the insulating state and vice versa.
Synthesis of Nanocrystalline Hexagonal Diamond Films in Organic Solvents by Femtosecond Laser Irradiation
Authors: Hu Anming , Duley Walt W.
Published: April 2011

Nanocrystalline diamond films have been synthesized on various substrates by 800 nm fs laser irradiation of a variety of organic solvents including acetone, pentane, hexane, heptane, octane, dodecane, and hexadecane in the presence of a transition metal catalyst. 632 nm Raman spectra display a strong vibration mode at 1308 cm−1 characteristic of hexagonal diamond. X-ray photoelectron spectra confirm that the film is mainly sp3-bonded carbon containing a low concentration of sp2-bonded inclusions. Film microstructure shows that these films are assembled from nanoparticles having an average size of < 100 nm. Analysis of the liquid after irradiation using HPLC techniques indicates that polyyne molecules are also synthesized during irradiation. It is possible that these species are formed as the products of ion chemistry following Coulomb explosion. This process may enable a new method for the creation of nanocrystalline hexagonal diamond layers for micro-electronic and other applications.
Role of Nucleation on the Growth of Nanocrystalline Diamond (NCD) Films: A Particular Study in the Fabrication of Micro-cantilevers
Authors: Jeedigunta Sathyaharish , Spagnol Priscila , Bumgarner John , Kumar Ashok
Published: April 2011

The effect of ultrasonic method of seeding on the growth of nanocrystalline diamond (NCD) films has been studied by investigating the nucleation densities of two nanodiamond slurries- 1) nanodiamond powder suspended in acetone 2) mixture of titanium nanopowder and nanodiamond powder suspended in acetone. The former has resulted in a lower nucleation density on the order of 108 cm−2 while the later has increased the nucleation density by over two orders (>1010 cm−2) of magnitude. NCD films were grown on Si(100) substrates in a Cyrannus I Iplas microwave plasma enhanced chemical vapor deposition (MPECVD) reactor using 0.5% CH4, 1% H2 and 98.5% Ar gas chemistry at a substrate temperature of ∼ 750°C, pressure of 135 T and a microwave power of 1.8 kW. The double anchored cantilever structures with NCD as structural material have been fabricated by conventional photolithography. It was observed that the films grown after pre-treating the substrates in pure nanodiamond slurry have not provided a complete coverage at the anchor regions of the cantilevers due to the lower nucleation density. Hence during the sacrificial oxide etch, the anchor regions did not adhere well to the substrate and the entire structures got detached from the substrate. But on the other hand, the films grown by seeding the substrates in a suspension of titanium nanopowder and diamond nanopowder showed complete film coverage and consequently very good bonding to the Si substrate at the anchor pads. In this case, the cantilevers have been successfully released without any problems at the anchor pads. Further the mechanical properties of the films were conducted by evaluating the Young's modulus and the hardness by nano-indentation technique.
Key Projections on Future PV Performance, Market Penetration and Costs, with Special Reference to CdTe and Other Thin Film Technologies
Authors: Raugei Marco , Frankl Paolo
Published: April 2011

The authors have drafted three alternative scenarios for the technological improvement and market penetration of photovoltaics in the next four decades, based on the preliminary results of the EU FP6 Integrated Project NEEDS, Research Stream 1a. The long-term diffusion of PV is foreseen to depend on the achievable module efficiencies and on the maturity of the different technologies in terms of their manufacturing costs, energy pay-back times, additional BOS costs, and even raw material reserves. Last but not least, the co-evolution of a suitable energy storage network (e.g. hydrogen) is also foreseen to be a mandatory requirement. Cumulative installed capacity worldwide is projected to reach 9,000 GWp in 2050 in the most optimistic scenario, which is reduced to 2,400 GWp in the intermediate scenario. In the third “pessimistic” scenario the current economic incentives are not assumed to be sustained long enough to allow PV to become competitive with bulk electricity, resulting in a stunted market growth (500 GWp in 2050). The resulting predictions in terms of costs range from 0.50 to 1.50 €/Wp in 2050, respectively corresponding to 2 - 8 €-cents per kWh in Southern Europe and 4 - 14 €-cents per kWh in Northern Europe. Within the framework of these three general scenarios, special attention is then put to the role that is likely to be played by thin film technologies, namely amorphous Si, CdTe and CIS/CIGS. These technologies are expected to collectively reach a market share of approximately 45% by as early as 2025 in all but the most pessimistic scenario, wherein the same goal is put off until 2050. Marked increases in module efficiencies and material and energy consumption are also expected, to varying degrees depending on the assumptions made in the three scenarios.
Nano-Structured Materials to Address Challenges of the Hydrogen Initiative
Authors: Berube Vincent , Dresselhaus Mildred
Published: April 2011

Since the publication of the 2003 report on Basic Energy Needs for the Hydrogen Economy, many important advances in hydrogen research have occurred, a cadre of enthusiastic researchers has entered the field with great interest shown by students, and private industry has made significant commitment to this technology and investment in its development worldwide. Concurrently, other energy technologies have made major strides forward. These technologies must be evaluated for their scalability, usability, cost and life cycle footprint on the environment. This overview discusses these topics and looks toward the role for the hydrogen economy into our energy future.
Metal Hydrides for Hydrogen Storage
Authors: Graetz Jason , Reilly James J , Wegrzyn James
Published: April 2011

The emergence of a Hydrogen Economy will require the development of new media capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides, where hydrogen is chemically bonded to the metal atoms in the bulk, offer some hope of overcoming the challenges associated with hydrogen storage. Many of the more promising hydrogen materials are tailored to meet the unique demands of a low temperature automotive fuel cell and are therefore either entirely new (e.g. in structural or chemical composition) or in some new form (e.g. morphology, crystallite size, catalysts). This proceeding presents an overview of some of the challenges associated with metal hydride hydrogen storage and a few new approaches being investigated to address these challenges.
Science and Prospects of Using Nanoporous Materials for Energy Absorption
Authors: Chen Xi , Qiao Yu
Published: April 2011

With its ultra-large specific surface area, a nanoporous material is an ideal, yet relatively unexplored, platform for accepting or actuating liquids, with potential performance gains for energy dissipation and output typical of disruptive technologies. Our experimental and theoretical results indicate either dramatically improved performance or unique combinations of properties and capabilities not attainable in conventional materials, which make the novel nanoporous structures studied herein very attractive as advanced protective intelligent systems.
Effect of Water Vapor and SOx in Air on the Cathodes of Solid Oxide Fuel Cells
Authors: Kim Seon Hye , Ohshima Toshihiro , Shiratori Yusuke , Itoh Kohei , Sasaki Kazunari
Published: April 2011

Ambient air is used as an oxygen source in SOFCs to be commercialized. Various chemical species which can lead to poisoning of SOFC cathodes are included as minor constitutions in air, such as water vapor, SOx, NOx and NaCl etc. However, their effects on the cathode performance have not yet well known, even though they are expected to cause a degradation of the electrode performance and to reduce the long-term durability of SOFCs. Therefore, in this study, we focused on the poisoning caused by water vapor and SOx in the oxygen source to clarify their effects on SOFCs performances and to reveal the degradation mechanism of cathodes. SOFCs with typical electrolyte-supported structure were used in this work, which were composed with ScSZ (10 mol% Sc2O3, 1mol% CeO2, 89 mol% ZrO2) plate with the thickness of 200 µm as electrolyte, NiO-ScSZ (mixture of 56 wt% NiO and 44 wt% ScSZ) porous layer as anode, and two cathode layers of LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ (mixture of 50 wt% LSM and 50 wt% ScSZ). Power generation characteristics of the cells had been analyzed by measuring cell voltage at a constant current density (200 mA/cm2) and by comparing changes in cell impedance, upon supplying the artificially-contaminated air with water vapor or SOx, to the SOFC cathodes at various operational temperatures. High-resolution FESEM (S-5200, Hitachi) was used to analyze microstructural changes caused by the impurities. Mg Kα radiation from a monochromatized X-ray source was used for XPS measurements (ESCA-3400, KRATOS). AC impedance was measured at various temperatures under the open circuit voltage condition by an impedance analyzer (Solatron 1255B/SI 1287, Solatron), in a frequency range from 0.1 to 105 Hz with an amplitude of 10 mV.
Life Cycle Assessment of Future Fossil Technologies with and without Carbon Capture and Storage
Authors: Dones Roberto , Bauer Christian , Heck Thomas , Mayer-Spohn Oliver , Blesl Markus
Published: April 2011

The NEEDS project of the European Commission (2004-2008) continues the ExternE series, aiming at improving and integrating external cost assessment, LCA, and energy-economy modeling, using multi-criteria decision analysis for technology roadmap up to year 2050. The LCA covers power systems suitable for Europe. The paper presents environmental inventories and cumulative results for selected representative evolutionary hard coal and lignite power technologies, namely the Ultra-Supercritical Pulverized Combustion (USC-PC) and Integrated Gasification Combined Cycle (IGCC) technologies. The power units are modeled with and without Carbon Capture and Storage (CCS). The three main technology paths for CO2 capture are represented, namely pre-combustion, post-combustion, and oxy-fuel combustion. Pipeline transport and storage in geological formations like saline aquifers and depleted gas reservoirs, which are the most likely solutions to be implemented in Europe, are modeled for assumed average conditions. The entire energy chains from fuel extraction through, when applicable, the ultimate sequestration of CO2, are assessed, using ecoinvent as background LCA database.

The results show that adding CCS to fossil power plants, although resulting in a large net decrease of the CO2 effluents to the atmosphere per unit of electricity, is likely to produce substantially more GHG than claimed by near-zero emission power plant promoters when the entire energy chain is accounted for, especially for post-combustion capture technologies and hard coal as a fuel. Besides, the lower net power plant efficiencies lead to higher consumption rate of non-renewable fossil fuel. Furthermore, consideration of the full spectrum of environmental burdens besides greenhouse gas (GHG) results in a less definite picture of the energy chain with CCS than obtained by just focusing on GHG reduction.
The Fuel Cycles of Electricity Generation: A Comparison of Land Use
Authors: Kim Hyung Chul , Fthenakis Vasilis
Published: April 2011

We investigate the area of land used and/or transformed during conventional (i.e., coal, natural gas and nuclear), and renewable fuel cycles (i.e., photovoltaics, wind, biomass, and geothermal). Both direct and indirect land use/transformation are examined in a life cycle framework. For average US insolation, the photovoltaic fuel cycle disturbs the least amount of land per GWh among renewable options, requiring less area than the coal fuel cycle. Renewable technologies could harvest infinite amount of energy per unit area and eliminates the need for restoring disturbed mine lands. Further investigations would be necessary for secondary and accidental land disturbance by conventional fuel cycles through transport of effluents and emissions to adjacent land.
Hydrogen Degradation Property of Electrochemically Charged Aluminum
Authors: Suzuki Hiroshi , Kobayashi Daisuke , Takai Kenichi , Hagihara Yukito
Published: April 2011

Degradation property of aluminum due to hydrogen is studied. Hydrogen is introduced by electrolysis charge in aqueous solution with addition of 0.1 mass % NH4SCN as a hydrogen recombination poison. The amount of hydrogen and its existing state in the material is analyzed by hydrogen desorption curves measured by the thermal desorption spectroscopy. The hydrogen desorption curves of charged aluminum showed two peaks, one at less than 100 °C and the other around 400 °C. The existing state of hydrogen relate to each peaks are identified as weakly trapped solute hydrogen to vacancy and free hydrogen molecule located in cavities that exists in the bulk of the material. Tensile properties are obtained to determine degradation property of the material due to hydrogen. The effect of hydrogen on degradation of charged aluminum is analyzed in terms of interaction between hydrogen and vacancy or dislocation. Solute hydrogen and cavities are found to affect ductility of aluminum, whereas hydrogen molecule in cavities has no effect.
The Stability and Reversibility of TiCl3 Doped LiBH4
Authors: Au Ming , Jurgensen Arthur R , Spenser William A , Anton Donald L , Pinkerton Frederick E
Published: April 2011

In an effort to develop reversible metallic borohydrides with high hydrogen storage capacities and low dehydriding temperature, modifications to LiBH4 with metal halides TiCl3 have been conducted. Adding TiCl3 to LiBH4 effectively reduced the dehydriding temperature through an ion exchange interaction by producing instable transition metal borohydrides and lithium salts. The material LiBH4+0.1TiCl3 desorbed 3.5wt% and 8.5wt% hydrogen at 150°C and 450°C respectively. Subsequent re-absorption of 6wt% hydrogen at 500°C and 70 bars was observed. The XRD analysis of the rehydrided samples confirmed the partial reformation of LiBH4. However, adding more TiCl3 made material more volatile and irreversible. TGA-RGA analyses indicated diborane evolution during dehydrogenation resulting in unrecoverable capacity loss and irreversibility. TiCl3 reduced LiBH4 stability and also made material irreversible.
A New Concept of Hydrogen Storage Using Lithium Hydride and Ammonia
Authors: Kojima Yoshitsugu , Hino Satoshi , Tange Kyoichi , Ichikawa Takayuki
Published: April 2011

It was indicated that H2 is generated by the reaction of LiH and NH3. After H2 generation, the byproduct LiNH2 was recycled back to LiH under H2 flow condition at 500K.
Thermodynamic Modeling of Plutonium Oxide Containing Americium
Authors: Hirota Masayuki , KUROSAKI Ken , UNO Masayoshi , MIWA Shuhei , OSAKA Masahiko , TANAKA Kenya , YAMANAKA Shinsuke
Published: April 2011

Thermodynamic modeling has been performed for O-Am binary system and O-Pu-Am ternary system on the basis of thermodynamic data available in the literature. The interaction parameters of the excess Gibbs energies of the fluorite structure FCCC1 phase in the O-Am and the O-Pu-Am systems were evaluated with respect to the deviation from the ideal solution in oxygen potential, respectively. The thermodynamic modeling used in this study is based on the CALculation of PHAse Diagram (CALPHAD) technique.
In-situ Formation of Bismuth-Based Iodine Waste Forms
Authors: Nenoff Tina , Krumhansl James L. , Rajan Ashwath
Published: April 2011

We investigated the synthesis of bismuth oxy-iodide and iodate compounds, in an effort to develop materials for iodine recovery from caustic waste streams and/or final waste disposal if repository conditions included ambient conditions similar to those under which the iodine was initially captured. The results presented involve the in-situ crystallization of layered bismuth oxide compounds with aqueous dissolved iodine (which resides as both iodide and iodate in solution). Although single-phase bismuth oxy-iodide materials have already been described in the context of capturing radioiodine, our unique contribution is the discovery that there is a mixture of Bi-O-I compositions, not described in the prior work, which optimize both the uptake and the degree of insolubility (and leachability) of iodine. The optimized combination produces a durable material that is suitable as a waste form for repository conditions such as are predicted at the Yucca Mountain repository (YMP) or in a similar type of repository that could be developed in coordination with iodine production via Global Nuclear Energy Program (GNEP) production cycles.
New Opportunities in Existing Thermoelectric Materials: Grain Boundary Engineering in Pulverized p-Bi2Te3 System
Authors: He Jian , Ji Xiaohua , Su Zhe , Gothard Nick , Edwards Justine , Tritt Terry M.
Published: April 2011

Grain boundary scattering provides an effective avenue to lower the thermal conductivity in polycrystalline thermoelectric materials, but it is hard to do this without simultaneously degrading the power factor that is the product of electrical conductivity and thermopower. An immediate question arises as to whether one can fabricate a thermoelectrically favorable grain boundary?

In this paper we present a proof-of-principle grain boundary engineering study in the pulverized p-Bi2Te3 system. Utilizing the lately developed hydrothermal nano-coating technique, we fabricated an Alkali-metal(s)-containing surface layer with few tens of nm thick on the p-Bi2Te3 bulk reference grain, where it becomes part of the grain boundary upon hotpressing densification. The electrical resistivity, thermopower, thermal conductivity and Hall coefficient measurements constitute solid evidence that this heterogeneous layer helps decouple the otherwise inter-related resistivity, thermopower and thermal conductivity. To optimize the figure of merit ZT, we carefully varied the ratio between Na, K and Rb concentrations. It was found that the sample treated in the solution with Na/Rb =1:2 achieved a ZT comparable with that of the commercial ingot; in the mean time, the compatibility factor and robustness of device were considerably improved. In principle this technique can be applied to other existing polycrystalline thermoelectric materials as a new “tuning knob”.
NANOCOMPOSITES TO ENHANCE ZT IN THERMOELECTRICS
Authors: Dresselhaus Mildred , Chen Gang , Ren Zhifeng , Fleurial Jean-Pierre , Gogna Pawan , Tang Ming Y , Vashaee Daryoosh , Lee Hohyun , Wang Xiaowei , Joshi Giri , Zhu Gaohua , Wang Dezhi , Blair Richard , Bux Sabah , Kaner Richard
Published: April 2011

The concept of using “self-assembled” and “force-engineered” nanostructures to enhance the thermoelectric figure of merit relative to bulk homogeneous and composite materials is presented in general terms. Specific application is made to the Si-Ge system for use in power generation at high temperature. The scientific advantages of the nanocomposite approach for the simultaneous increase in the power factor and decrease of the thermal conductivity are emphasized along with the practical advantages of having bulk samples for property measurements and a straightforward path to scale-up materials synthesis and integration of nanostructured materials into thermoelectric cooling and power generation devices.
Defect Clustering and Nanostructure Formation in PbTe-based Bulk Thermoelectrics
Authors: Hoang Khang , Mahanti S. D.
Published: April 2011

In recent years, LAST-m (AgPbmSbTem+2) and related materials have emerged as potential high performance high temperature thermoelectrics. One example is LAST-18. When optimally doped, this compound has thermoelectric figure of merit ZT=1.7 at 700K. This large ZT is most likely due to the low lattice thermal conductivity, caused by phonon scattering from nanostructures. These nanostructures involve clustering and ordering of Ag, Sb, and Pb ions. The origin of these nanostructures has been studied using Monte Carlo (MC) simulation of an ionic model and ab initio studies of pair interaction energies. Effects of these substitutions on the band structure near the gap and their implications on transport properties are briefly discussed.
Optimization of High Thermoelectric Figure-of-Merit in p-type Ag1-x(Pb1-ySny)mSb1-zTem+2
Authors: Ahn Kyunghan , Kanatzidis Mercouri G
Published: April 2011

The Ag1-x(Pb1-ySny)mSb1-zTem+2 compounds have been found to exhibit high performance p-type thermoelectric properties and are now being considered for practical applications. In this paper, various m values and silver concentrations were investigated to determine the effect on thermoelectric properties. Also, the charge-compensated compounds were studied in order to eliminate the problem of excess tellurium evaporation at high temperature.
Thermoelectric Properties of Phase Separated Composite of Ln-Doped SrTiO3 and TiO2 Micro Crystals
Authors: Fuda Kiyoshi , Murakami Kenji , Sugiyama Shigeaki
Published: April 2011

It seems that no satisfactory TE property has been found in n-type oxide bulk materials even though Al-doped ZnO and La-doped SrTiO3 have high thermoelectric (TE) responses. Difficulty in developing high-performance TE materials seems to lie in finding low thermal conductivity in such oxides. The purpose of this study is to find a possibility to make an n-type TE oxide bulk material having low thermal conductivity and excellent TE properties as well. For this purpose, we fabricated and examined a series of composites constructed of TiO2 and Ln-doped SrTiO3 fine crystals. The composites were prepared via two processing steps: (1) precursor oxide preparation by wet processes; (2) sintering by using spark plasma sintering (SPS) apparatus. The microscopic structure was examined by using scanning electron microscope (SEM; HITACHI S-4500 model) attached with an energy dispersive x-ray spectroscopy. The electrical conductivities and the Seebeck coefficients were measured simultaneously using an ULVAC ZEM-1 instrument in helium atmosphere. The thermal diffusivities were measured by a laser flash method in vacuum. The composites obtained here were found to commonly have a mosaic type texture constructed of TiO2 and SrTiO3 fine particles with a typical size of 500 nm. The thermal conductivity values measured for three samples with different contents are ranged between 3 and 4 Wm-1K-1 in the temperature range from room temperature to 800 C. The values are apparently lower than the value for single crystal SrTiO3 samples presented in literature. Taking account the other TE data, e.g. Seebeck coefficient and electrical conductivity, we calculated dimensionless figure of merit, ZT, to be at maximum 0.15 at 800°C.
The Effect of Bi Addition on Thermoelectric Properties of the Sintered Heusler Fe2VAl Alloy
Authors: Mikami Masashi , Kobayashi Keizo , Hazumi Kiminori , Nishino Yoichi
Published: April 2011

A Fe2VAl0.9Si0.1/Bi composite were fabricated using pulse-current sintering technique with mixed powder prepared by mechanical alloying. Since the raw powders were finely pulverized into nanometer sized crystallite and rapidly sintered to suppress grain growth during heat treatment, microstructural composite was obtained. The composite was consisted of Fe2VAl0.9Si0.1 grains with the size of 200-300 nm and nanometer-sized Bi particles. The size of the Bi particle decreased with the increase in the milling processing time, while the size of the Fe2VAl0.9Si0.1 grains showed no variation. The thermal conductivity of the composite decreased with the reduction of the Bi particle size, because of the increase in the number of hetero junction, at which phonons were scattered. On the contrary, the electrical conductivity was less affected by the incorporation of nanometer-sized Bi particles. This means that the hetero junction between Fe2VAl0.9Si0.1 and Bi has little effect on the carrier traveling or the dispersion of highly conductive Bi particles enhanced electrical conductivity. Although Seebeck coefficient was reduced by a negative effect of Bi incorporation on the Fe2VAl0.9Si0.1 crystal structure, the introduction of Bi nanoinclusions in the sintered Heusler material was effective to reduce the thermal conductivity without degradation of electrical conductivity and consequently improved the thermoelectric figure of merit.
Effect of Combined Addition of Silicon Carbide Whiskers and Fullerene Nanoparticles on Properties of Thermoelectric Zinc Antimonide
Authors: Itoh Takashi , Asari Nobuhisa , Kanetake Nobuyuki , Okada Akira
Published: April 2011

Thermoelectric power generation is a hopeful method harnessing waste thermal energy particularly covering a middle temperature range between 500 and 800K. A Zn4Sb3 compound is a promising “phonon glass electron crystal” material applicable to thermoelectric power generation around 700K. This material, however, has a problem of its brittleness. In this research, the silicon carbide whiskers were added into the Zn4Sb3 compound for overcoming the brittleness, and the fullerene nanoparticles were also added for improving the thermoelectric performance. The Zn4Sb3 compound was synthesized from mixture of pure zinc and antimony powders by a liquid-solid phase reactions method. Firstly, the synthesized compound powder was mixed with the fullerene nanoparticles. The planetary ball milling method was used in order to disentangle the fullerene agglomerate and to obtain a uniform mixture. Subsequently, the mixture was uniformly mixed with the SiC whiskers by the planetary ball milling. The final mixture was consolidated by the pulse discharge sintering. The synthesized phases were identified by XRD. The morphology of the whiskers after mixing was observed. The flexural strength and the thermoelectric properties of the sintered samples were measured. The length of SiC whiskers and the flexural strength were decreased with the mixing time. Though the addition of SiC whiskers lowered the thermoelectric performance, the combined addition of SiC whiskers and fullerene nanoparticles restored the performance by especially decrease of the thermoelectric conductivity owing to the phonon scattering.
Thermoelectric Oxides and Oxynitrides with Perovskite-type Structure
Authors: Weidenkaff Anke , Bocher Laura , Robert Rosa , Aguirre Myriam , Logvinovich Dmitry
Published: April 2011

Transition metal oxides and oxynitrides with perovskite-type structures are potential high temperature stable thermoelectric materials. With innovative soft chemistry synthesis procedures the crystallite size in complex oxide ceramics with perovskite-type structure can be decreased compared to classical synthesis routes and allows to lower the heat conductivity dramatically while a large power factor can be maintained at the same time. Submicron crystallites are beneficial to lower the lattice thermal conductivity without influencing the electron mobility.

In this work, perovskite-type cobaltates, molybdates and manganates are studied. The influence of heterostructures and nanocrystalline domains in perovskite oxides/oxynitrides and the correlation with transport properties and Seebeck coefficient will be discussed.
Thermoelectric properties of Bi2Te3 based thin films fabricated by pulsed laser deposition
Authors: Higomo Shun , Yagi Takashi , Obara Haruhiko , Yamamoto Atsushi , Ueno Kazuo , Iida Tsutomu , Taketoshi Naoyuki , Baba Tetsuya
Published: April 2011

Bi2Te3-based thin films were fabricated on glass substrates by the pulsed laser deposition (PLD) method. The vapor pressures of Bi and Te are significantly different, so controlling the stoichiometric composition is difficult when using conventional physical vapor deposition techniques, and the thermoelectric properties of Bi2Te3 films are sensitive to the film composition. PLD is a promising technique for the fabrication of telluride-based films such as Bi2Te3 due to its superior capability for controlling the film composition. Another advantage of PLD is the flexibility that it allows in terms of atmosphere in the reaction chamber; high concentrations of gases such as oxygen or argon can be introduced. We have measured various compositions of Bi2Te3 based films, and have identified the optimal compositions for both n-type and p-type material. The thermal conductivities of these Bi2Te3 films were evaluated by an exact measuring system, and the results were twice as low as those of conventional bulk materials. These results suggest that PLD has significant advantages for the deposition of in-plane Bi2Te3-based thin films.
Application of the Thermal Quadrupole Method in the Characterization of Thermoelectric Modules
Authors: Hatzikraniotis Euripides , Samaras Ioannis , Georgakaki Dimitra , Paraskevopoulos Konstantinos M
Published: April 2011

Measurements of assembled thermoelectric (TE) modules commonly include investigations of the module output power versus load resistance. Using an AC electrical measurement for TE modules, a model of equivalent passive RC circuit has been developed and tested for both the thermal and electrical characteristics of the module. In this work we present and analyze data of a commercially available module, using equivalent passive RC circuit, to examine, explain and model the electro-thermal activity in the module. In addition data we analyzed by thermal quadrupole theory. Measurements were taken over the frequency range of 0,5mHz to 50 Hz and the device performance (ZT) was evaluated from measured data.
New Thermoelectric Arsenides and Antimonides for High Temperature Applications
Authors: Xu Hong , Soheilnia Navid , Zhang Huqin , Alboni Paola N. , Tritt Terry M. , Kleinke Holger
Published: April 2011

Three different materials crystallizing in the cubic Ir3Ge7 type are under investigation in our group, namely Mo3(Sb,Te)7, Nb3(Sb,Te)7, and Re3(E,As)7 (with E = Si, Ge, Sn). Our electronic structure calculations reveal a band gap to occur at 55 valence-electrons in all three cases, namely Mo3Sb5Te2, Nb3Sb2Te5, and Re3EAs6. Cubic holes exist in these structures that may be filled with small cations such as 3d transition metal atoms. Ni0.06Mo3Sb5.4Te1.6 is a degenerate p-type semiconductor that reaches ZT = 0.96 at 750°C, while Re3Ge0.6As6.4 is a degenerate n- type semiconductor with slightly lower ZT values. Preliminary results indicate that the Re3(Sn,As)7 system may be the most promising of the rhenium arsenides.
Converting Traditional Materials Labs to Project-based Learning Experiences: Aiding students' Development of Higher-order Cognitive Skills
Authors: Vanasupa Linda , Chen Katherine C , Stolk Jonathan , Savage Richard , Harding Trevor , London Blair , Hughes William
Published: April 2011

Against a backdrop of compelling societal needs, graduates in science and engineering now must master their disciplines and demonstrate a sophisticated level of cognitive, affective and social development. This has lead a number of national and international commissions on science and engineering to urge educators to re-think the way in which STEM disciplines are taught. We have chosen to “repackage” a traditional undergraduate materials engineering curriculum in a form designed to promote the development of higher-order cognitive skills like self-directed learning and design. Classic metallurgy experiments have been converted to project-based learning experiences where students are put in the role of “designers” of problem solutions and faculty play the role of coaches. These include: designing, prototyping and marketing of a cast metal object; systems designing, building and testing of a fiber optic spectrometer; product improvement of a prosthetic device; design and evaluation of a heat treatment process for roller bearings. Projects were designed to leverage known relationships within the educational psychology literature that enable deeper learning. Evaluation of 36 juniors in a project-based learning course (i.e., the test cohort) against a quasi-control group in traditional engineering courses showed that the test cohort scored significantly higher on two motivation scales shown to be critical components in self-directed learning (p<0.001). The test cohort also reported a significantly higher use of peers as learning resources than the quasi-control group. Their motivation scores also correlate highly with self-reported comfort with several aspects of design, implying that their motivation contributes significantly to students' ability to effectively engage in the design process. In this paper, we present examples of the materials engineering projects that were designed and implemented, and the design features that enable them to promote the development of sophisticated cognitive functioning.
The Use of A Multidisciplinary Project to Expand the Materials Science Curriculum
Authors: Heard Robert , Matthews Deanna
Published: April 2011

A special interdisciplinary project course was offered in the Fall of 2006 within the Carnegie Institute of Technology at Carnegie Mellon University. The course was open to students from across the university, it drew participants from Civil and Environmental Engineering, Engineering and Public Policy, Materials Science and Engineering, Architecture, the School of Design. This multidisciplinary collection of students formed the necessary knowledge base to approach the various tasks of the project. Each student was to rely on their academic experience and talents to contribute to the work, while simultaneously learning from those in other disciplines. The participating material science and engineering were juniors acquainted with fundamental of materials. Some students were taking courses involving steel making process and steel mechanical properties concurrently. Students in civil and mechanical engineering and architecture are familiar with structural design and construction processes. Students in engineering and public policy and environmental engineering have experience with life cycle assessment and environmental impacts. The collaborative group experience introduced students to how disciplines interact in the real world, encouraging them to pursue their own interests in broader areas.

The project consisted of three efforts assessing life cycle impact in terms of energy consumption, greenhouse gas emissions, and economic costs of equivalent products made from both steel and wood The first effort involved comparison of steel products versus wood products in existing designs. The second, looked at the optimization of steel products to improve design options and the third tried to identifying opportunities to leverage the use of steel materials in green building design and construction, based on certification requirements established by the US Green Building Council and the Leadership in Energy and Environmental Design (LEED) rating system.

At Carnegie Mellon, the Green Design Initiative researchers have been leaders in life cycle assessment methodology development and assessment, and have a history of merging students and faculty from across the university into research teams. This multidisciplinary project was good example of how common topics can be exploited to provide excellent discovery opportunities for undergraduate engineering programs.
Thermal Expansion and Residual Stress in Ancient Chinese Bronze Castings
Authors: Taube Michelle , McCarthy Blythe
Published: April 2011

Ancient Chinese bronze vessels from the Shang to Zhou dynasties (c. 1500 - 221 BCE) were cast using piece molds. Several large vessel shapes, especially those with legs, have been found to be made in several steps with the vessel body cast onto previously-made legs or other appendages. In this situation the molten metal contacts and must attach to the solid pieces from the first casting. Similar interfaces are found at solid metal mold spacers or chaplets used in the casting process. Previous researchers showed that the casting can exhibit concentration gradients and evidence of slip in the regions around these interfaces. In this work, we studied the thermal expansion of the bronze at cast-on joints in ancient Chinese bronzes using thermomechanical analysis (TMA). The results are compared with those from reference lead-tin bronze alloys.
Fabrication of PdxNiyP100-x-y Metallic Glass Film by Electroless Alloy Plating and its Catalyst Activity
Authors: Imamura Yoshihide , Sone Masato , Shibata Akinobu , Ishiyama Chiemi , Higo Yakichi
Published: April 2011

Pd-Ni-P films were systematically plated using a mixture of Pd and Ni-P plating solutions. The films were plated by electroless alloy plating using three Pd/Ni-P mixture ratios (1/1, 3/1, and 1/3) at plating temperatures adjusted within a range from 303 to 333K. An increase in the Ni-P mixture ratio or in the plating temperature led to an increase in the Ni content of the plated film and a decrease in the Pd content. The P content of the plated film remained almost constant. These results indicate that the composition of the fabricated film can be effectively controlled by adjusting the plating temperature and mixture ratio. The plated film had a flat surface morphology without defects such as pinholes or nodules. TEM observation of the film revealed an amorphous structure. DSC analysis during heating revealed an endothermic peak and exothermic peak corresponding to the glass transition and crystallization, respectively. On the basis of these results, we concluded that the plated Pd-Ni-P film was metallic glass. The plated Pd-Ni-P film was also confirmed to have catalytic activity, as the Ni-P alloy was plated directly onto the film without catalyzation by electroless plating. The high flatness and uniformity of the surface of the Ni-P film plated onto the Pd-Ni-P film suggests that the Ni-P film grew via a one-dimensional growth mechanism.
Free Volume Relaxation Process in Zr50Cu40Al10 Bulk Metallic Glass Studied by Positron Annihilation Techniques
Authors: Ishii Akito , Hori Fuminobu , Iwase Akihiro , Yokoyama Yoshihiko , Konno Toyohiko J
Published: April 2011

Structural relaxation around free volume in Zr50Cu40Al10 bulk metallic glass (BMG) during isothermal annealing at 473, 573 and 673 K which are below glass transition temperature Tg =675 K have been investigated by positron annihilation lifetime (PAL) and coincidence Doppler broadening (CDB) measurements. The trends of change in positron lifetime, which correspond to the size of free volume at each annealing temperature, have a good correlation with their density change. These annealing processes obey a stretched exponential relaxation function (KWW: Kohlrausch-Williams-Watts law). Fitting parameters of KWW function, with relaxation time t0 and β, in each temperature were determined. These relaxation parameters depend on the annealing temperature, suggesting the distribution of activation energy for structural relaxation. Moreover, the profile of electron momentum distribution around free volume derived by CDB spectrum during annealing showed no appreciable change at each temperature. These facts suggest that long range chemical ordering, particularly around the free volume, dose not take place essentially.