bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ternary Skutterudites: Anion Ordering and Thermoelectric Properties
Authors: Vaqueiro Paz , Sobany Gerard G. 
Published: April 2011

AbstractThe 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

AbstractWe 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

AbstractWe 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

AbstractWe 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

AbstractWith 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

AbstractThe 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

AbstractVery 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

AbstractWe 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

AbstractWe 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

AbstractThe 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

AbstractScience 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

AbstractThe 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

AbstractAttracting 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

AbstractGodin 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

AbstractThe 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

AbstractThe 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

AbstractMetallic 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

AbstractThe 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.
Glass Formation Dependence on Casting Atmosphere in a Zr-Al-Ni-Cu-Pd Alloy System
Authors: Setyawan Albertus Deny , Kato Hidemi , Saida Junji , Inoue Akihisa 
Published: April 2011

AbstractA Zr65Al7.5Ni10Cu17.5-xPdx (x=0-17.5 at. %) alloy system is found to exhibit a unique dependence of glass-forming ability (GFA) on casting atmosphere during mold-casting process. High-Pd containing alloys (x=7.5-17.5) showed a remarkable increase of critical size (dc) for glass formation, in contrast with the low-Pd containing alloys (x=0-5) in which no significant change in dc was observed, as the pressure of Ar atmosphere varied from vacuum to ambient. The origin of the phenomenon has been successively unveiled by correlating the cooling characteristic during casting process and phase transformation behavior during continuous cooling of the alloy system. The consequence in the structure and property control is investigated and discussed in detail.
Nanoindentation Analysis of Plasticity Evolution during Spherical Microindentation of Bulk Metallic Glass
Authors: Yoo Byung-Gil , Jang Jae-il 
Published: April 2011

AbstractUnlike most of crystalline metals, metallic glasses are known to exhibit a fully-plastic behavior or work softening during mechanical deformation. To analyze the characteristics of the deformed region, here a series of instrumented micro- and nano-indentation experiments were performed on a Zr-based bulk metallic glass (BMG) with geometrically self-similar sharp indenter as well as spherical indenters. First, we performed instrumented micro-indentation tests with a spherical indenter on the bonded interfaces of the BMGs. Although adhesive (used for bonding the interfaces) might significantly affect the deformation mode by reducing the constraint, the evolution of subsurface plasticity during spherical indentation was clearly observed. Subsequently, the subsurface plasticity underneath the hardness impressions was systematically examined through nanoindentation. The results are discussed in terms of major change in mechanical responses of BMGs before and after indentation-induced deformation.