bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melt Spinning Preparation of Bismuth Telluride and Partially Alloying with IV-VI Compounds for Thermoelectric Application
Authors: Boettner Harald , Ebling Dirk , Jacquot Alexandre , Kühn Uta , Schmidt Jürgen , Boettner Harald 
Published: April 2011

AbstractThe melt spinning technique (MST) combined with post annealing processes is evaluated for the development of thermoelectric nanocomposites. The evaluated ones are based on two components almost immiscible in solid state but with crystallographic correlation. One is taken from the V-VI-components system and the other one from the IV-VI-components system. This concept was applied to p-(Bi0,2Sb0,8)2Te3 and to p-[(Bi0,2Sb0,8)2Te3]1-xPbTex composites. MST samples of all types were characterised for some structural and thermoelectric properties. All V-VI materials are clearly textured after MST and show no deterioration concerning the thermoelectric properties even after subsequent annealing processes. Structural analysis of p-[(Bi0,2Sb0,8)2Te3]1-xPbTex composites gave significant hints for oriented precipitates of a IV-VI-rich phase incorporated into the V-VI-rich matrix. The thermoelectric figure of merit of the evaluated composites could be enhanced by suitable annealing procedures of both the quenched bulk materials and the melt spin material.
Atomic Ordering, Electronic Structure, and Transport Properties of LAST-m Systems
Authors: Mahanti S. D. , Hoang Khang , Ahmad Salameh 
Published: April 2011

AbstractIn recent years, LAST-m (AgPbmSbTem+2) and related materials have emerged as potential high performance high temperature thermoelectrics. These compounds are obtained by starting from PbTe, and replacing pairs of Pb2+ ions by (Ag1+, Sb3+) pairs. 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 very low lattice thermal conductivity, caused by phonon scattering from nanostructures. These nanostructures involve clustering and ordering of Ag, Sb, and Pb ions. Possible origins of this atomic ordering and how the presence of nanostructures affects the electronic structure near the band gap region are discussed. The temperature (T) dependence of electrical conductivity σ (∼T2.2 in the range 300K <T< 900K) in n-type PbTe is analyzed in terms of the T-dependence of different physical quantities contributing to transport. We find that the dominant contribution comes from the explicit T-dependence of relaxation time rather than its energy dependence. The T-dependence of chemical potential is also significant in the concentration range of interest. Electronic thermal conductivity for constant field (κel,E) and for constant current (κel,J) are found to differ considerably at high temperatures and the Weidemann-Franz (WF) law κel,J = LoσT, where Lo =2x10−8WΩ/K is the Lorentz number, overstimates κel,J by nearly 60% at 800K for carrier concentration n=5x1019/cm3. As a result, one tends to underestimate the lattice contribution κlatt = κexp - κel,J. We give theoretical values of effective Lorentz number L = κel.J/σT for different n and T.
Bulk Materials Research for Thermoelectric Power Generation Applications
Authors: Nolas George , Beekman Matthew , Martin Joshua , Wang Dongli , Lin Xiunu sophie 
Published: April 2011

AbstractThere are a variety of material systems employing different strategies in an effort to establish a new paradigm for thermoelectric materials performance. One approach is the PGEC, or “phonon-glass electron crystal”, approach were research towards optimization of the electrical properties of very low thermal conductivity materials is key. Other efforts focus on materials that exhibit high power factors via quantum-confinement or nano-scale affects. Still others focus on “engineering” metastable phases that possess properties that are distinct, if not unique, to solid state chemistry. All these approaches are valid and provide a fundamental knowledge base whereby present and future scientific materials discoveries will lead to new technological improvements. This paper focuses on bulk materials, in particular those material systems currently under investigation in the novel materials laboratory at the University of South Florida and the requirements and strategies for their optimization towards improved thermoelectric properties.
Preparation and Properties of Srn+1TinO3n+1 Ruddlesden-Popper Homologous Series by Metal-Citric Acid Complex Decomposition Method
Authors: Nishio Keishi , Fukuda Kazuhiko , Imai Tomohiro , Takenouchi Hirohumi , Mae Hideo , Fujimoto Masakatsu , Iida Tsutomu , Hamada Noriaki , Kineri Tohru , Watanabe Tsuneo 
Published: April 2011

AbstractWe investigated the Srn+1TinO3n+1 Ruddlesden-Popper homologous series. This material exhibits a wide range of electric behaviors, from a high-dielectric-constant tunable-paraelectric in its undoped form to a metallic superconductor when it is doped with a variety of elements.The Srn+1TinO3n+1 and the yttrium-doped Srn+1TinO3n+1 Ruddlesden-Popper homologous series were prepared through the thermal decomposition of a metal citric acid complex. The starting solution consisted of the raw materials strontium acetate and titanium alkoxide. Citric acid was used as the chelating agent, and ethanol and distilled water were mixed and used as a solvent. Single phase Sr2TiO4 and Sr3Ti2O7 were produced without creation of SrCO3 by heat-treatment at 1073 and 1473 K, respectively, for three hours. We were unable to produce single phase Sr4Ti3O10. The samples consisted of Sr4Ti3O10 and SrTiO3 phases. Scanning electron microscopy showed that the grain shape of the Sr2TiO4 was plate-like, while those of the Sr3Ti2O7 and Sr4Ti3O10 were not and the grains had large numbers of pores. High-density Sr2-xYxTiO4 (x= 0 to 0.06) ceramic samples were produced under hot-press conditions (1823 K for one hour at a uniaxial pressure of 31.2 MPa). Although the undoped samples were insulators, the yttrium-doped samples showed high electrical conductivity (i.e. that of Sr1.98Y0.02TiO4 was ρ= 8.5×10−5 Ωcm). The Seebeck coefficient of Sr1.98Y0.02TiO4 was –160.7 μV/K, and the thermal conductivity was 3.38 W/mK.
Reduced Thermal Conductivity by Low-Frequency Optic Phonons that Give Rise to Negative Thermal Expansion: Opportunities for Thermoelectrics?
Authors: White Mary Anne , Whitman Catherine A. 
Published: April 2011

AbstractWe have recently found that the negative thermal expansion (NTE) materials, ZrW2O8 and HfMo2O8, show exceptionally low thermal conductivity. We surmise that the mechanism is the efficient coupling of the low-frequency optic phonons that give rise to negative thermal expansion with the heat-carrying acoustic phonons. Although neither ZrW2O8 nor HfMo2O8 has suitable electronic properties for thermoelectric applications, perhaps the principle of reduced thermal conductivity by low-frequency optic phonons in NTE materials can be used to develop more efficient thermoelectric materials.
Transport Behavior and Thermal Conductivity Reduction in the Composite System PbTe-Pb-Sb
Authors: Sootsman Joseph , Kong Huijun , Uher Ctirad , Downey Adam , D'Angelo Jonathan James , Wu Chun-I , Hogan Timothy , Caillat Thierry , Kanatzidis Mercouri 
Published: April 2011

AbstractWe report the synthesis of nanostructured composite PbTe with excess Pb and Sb metal inclusions. Scanning and transmission electron microscopy reveal these inclusions in both the nano- and macroscales. The electrical conductivity and Seebeck coefficient dependence on temperature show unusual trends which depend on the inclusion Pb/Sb ratio. Several ratios showed marked enhancements in power factor at 700 K. The thermal conductivity of these composites is reported.
Thermoelectric Properties of Mixed-Metal Tellurides
Authors: Powell Anthony V , Guinet Fabien , Vaqueiro Paz , Wilcock Ian M , Jones Richard L 
Published: April 2011

AbstractA new series of thallium-containing materials, Tl1-xPbmATem+2 (A= Sb, Bi; m=10, 18; 0≤x≤0.3), has been prepared. Diffraction data reveal that a rocksalt-type structure is adopted at all compositions. Transport property measurements indicate n-type behaviour for the bismuth-containing materials and p-type for the antimony analogues. The reduced power factors for the latter, compared to the bismuth-containing materials, are primarily due to their more resistive nature. The highest power factors occur at a thallium deficiency in the range 0.1≤x≤0.2. Measured thermal conductivities are reduced from that of the binary telluride, suggesting that the materials may have potential as n/p-type components in device applications.
Addressing Broader Impacts through Research Center - Science Museum Partnerships
Authors: Alpert Carol Lynn 
Published: April 2011

AbstractThe National Science Foundation requires investigators to address the “broader impacts” of research in science, education, and society. NSF considers significant contributions in this area to include education and outreach activities designed to enhance scientific and technological understanding and to foster connections between research and service to society. Yet, organizations optimized for research and teaching often lack the expertise, tools, and resources for carrying out these activities, and lack connections to community-serving organizations and audiences intended for these kinds of engagements. It is for this reason that NSF offers the suggestion of partnering “with museums, nature centers, science centers, and similar institutions to develop exhibits in science, math, and engineering,” to “involve the public…in research and education activities,” and to provide “science and engineering presentations to the broader community.” [1] This sensible-sounding advice nonetheless offers little guidance to materials science and engineering researchers in the actual planning, design, implementation, and evaluation of effective educational outreach partnerships. This MRS Symposium proceedings briefing, preliminary to a more extensive treatment of the topic, presents particular aspects of the case for pursuing such partnerships as well as some suggestions for ensuring their effectiveness. The author is a Co-PI of the NSF Nanoscale Informal Science Education Network (NISE Net) and also manages three long-term NSF and NIH-funded research center partnership programs in place at the Museum of Science, Boston.
Inspiring 1000 Middle School Students at Princeton University's Materials Science and Engineering Expo
Authors: Steinberg Daniel , Swilley Shannon 
Published: April 2011

AbstractPrinceton Center for Complex Materials (PCCM) is a National Science Foundation-supported Materials Research Science and Engineering Center. The educational outreach team conducts many educational outreach programs. Since 2004, one of our largest k-12 education programs has been the Science and Engineering Expo at Princeton University (SEE Princeton) for middle school students in partnership with other outreach programs at Princeton University. The goals of the program are to allow hundreds of Princeton University scientists and engineers the opportunity to share their enthusiasm for science with middle school students, to instill excitement for science and engineering in the students, to expose the students to learning opportunities in science and engineering, and to introduce them to the field of materials science. This paper provides a brief guide to developing and conducting a science and engineering expo based on a successful model.
A Partnership Inspiring Interest in MSE Careers: The Center for Research on Interface Structures and Phenomena (CRISP)
Authors: Caragianis-Broadbridge Christine , Edgecumbe Heather , Osenko Greg , Lehman Ann , Alter Lisa , Tully John 
Published: April 2011

AbstractThe intent of the CRISP education and outreach effort is to use materials science as a vehicle for enhancing the scientific literacy and knowledge of kindergarten through post-graduate level students. A challenging part of our mission has been inspiring students to take the next step and consider further study (or a career) in the field of Materials Science and Engineering (MSE). The CRISP educational programs were developed through a partnership between Yale University, Southern Connecticut State University and the urban school district of New Haven, CT. An overview of the methods and results of both formal and informal educational program components will be presented for years one and two of the CRISP MRSEC. This paper will focus on two CRISP programs: 1) MRSEC Initiative for Multidisciplinary Education & Research (MIMER) and 2) “Exploring Materials Science” mobile kits. The evaluation data indicates that the approach used in developing these educational programs is important. Specifically, the impact of these programs is influenced by the students' ability to relate the acquired knowledge to real life applications and technologies. In particular, emphasizing career opportunities rather than just presenting content-based programs is a key element to increasing interest towards further study in Materials Science and Engineering.
HELICAL Learning Model Applied in a Nanotechnology for Science and Engineering Course
Authors: Peterson Eric , Reed Morgan , Gomes Jewel , Cocke David L. 
Published: April 2011

AbstractIn education, a popular model employed to represent the learning process is typically portrayed as a four-stage process signified by a cycle in a two-dimensional circular path. This cycle can be repeated by revisiting topics at increasing levels of sophistication in order to produce what is known as a spiral curriculum.In this presentation, a variation of Kolb's two-dimensional learning cycle model is offered that represents the learning cycle as if it were a three-dimensional spiral or helix, with successive turns associated with increases in Bloom's Taxonomic level. This representation is explored and developed, with a specific example from a chemical engineering course offered in Industrial Electrochemistry. This more comprehensive concept-centered model for the learning cycle explicitly includes higher order thinking skills to promote creative thinking, through the application of concepts and can be used to develop more effective curricula and course instruction. Specifically, our sample class consists of four teams, each of which is responsible for becoming expert in the concepts associated with an area of science and another of application. Transfer of content is student driven while topics are explored. Students teaching each other allows for synergistic enhanced motivation to explore, with concurrent ultimate improvement in the retention of core concepts by the entire course population.
Correlation Between Thermodynamic and Kinetic Properties of Glass-Forming Liquids
Authors: Senkov Oleg N. , Miracle Daniel B. 
Published: April 2011

AbstractCorrelations between three characteristic temperatures: glass transition,Tg, Kauzmann,Tk, and Vogel-Fulcher-Tammann,To, were identified from the analysis of more than 60 metallic and non-metallic glass-forming materials. It was found thatTg≥Tk≥ToandTkis the geometric mean ofTgandTo. The relationTk≥Toindicates that the excess total entropy of a super-cooled liquid ΔSapproaches zero at a higher temperature than the configurational entropy ΔSconf, and such behavior was explained by the stronger temperature dependence of the excess vibrational entropy of the liquid, ΔSvib, than that of the corresponding glass,. A relationship between the fragility indexm, reduced excess heat capacity ΔCp(Tg)/Sm, and reduced glass transition temperature,Trg, was identified using the found correlation between the characteristic temperatures.
Point Defects, Recovery Kinetics and Ordering in Irradiated Bulk Metallic Glasses
Authors: Petrusenko Yuri , Bakai Alexander , Borysenko Valeriy , Barankov Dmitro , Astakhov Oleksandr , Macht Michael-Peter 
Published: April 2011

AbstractThe problem of structural properties and structural defects of amorphous solids is still of vital importance. To make clear whether stable point defects exist in metallic glasses (MGs) or not, we have studied the accumulation and recovery kinetics of radiation defects in ZrTiCuNiBe and ZrTiCuNiAl bulk MGs irradiated with 2.5 MeV electrons at T ∼ 80 K. The electrical resistance measurements of the irradiated samples were performed. The recovery spectrum of irradiation-induced electrical resistance was measured for the 85–300 K temperature range. The most important result of the recovery experiments is that they clearly show the annealing stages for the irradiated samples. Two annealing peaks located at T∼150 K and T∼225 K are resolved for ZrTiCuNiBe glass. Similar peaks are also revealed for ZrTiCuNiAl. It can be concluded from the data that the defect mobility is a thermally activated process, and that the activation energy is not as high as that for vacancies in crystalline alloys. Thus, the data obtained testify in favor of the structure with “perfect” local ordering of atoms. It should be noted that this property is basic in the formulation of the polycluster model of amorphous solids.
Stability of the Pd-Co-Ni-Cu-P Metallic Glasses
Authors: Fukamaki Daisuke , Takeuchi Tsunehiro , Hasegawa Masashi , Soda Kazuo , Sato Hirokazu , Mizutani Uichiro 
Published: April 2011

AbstractStability of Pd-Co-Ni-Cu-P metallic glass was investigated in terms of free energy using first principle cluster calculations, thermal analysis, and photoemission spectroscopy measurements. We found that the internal energy of the Pd-based metallic glasses is dominated by the electronic structure near the Fermi level. The analyses on the electronic structure and local atomic arrangements indicate that the substitution of cobalt or a hypothetical atom Co0.5Cu0.5 for nickel in the Pd40Ni40P20 metallic glass decreases the free energy of the Pd-Ni-P metallic glass by increasing entropy without altering significantly internal energy. On the basis of the idea mentioned above, we prepared Pd28Co24Ni24P24, Pd25Co25Ni25P25 and Pd40Co40/3Ni40/3Cu40/3P20 metallic glasses. These metallic glasses certainly showed the nearly highest TX, which directly reflect the activation energy against crystallization, among the Pd-based metallic glasses ever reported.
Processing Map for Zr-based In-situ β Phase Composites
Authors: Lee Seung-Yub , Li John J.Z. , Suh Jin-yoo , Rhim Won-Kyu , Johnson William L. , Ustundag Ersan 
Published: April 2011

AbstractThe processing map for Zr-based bulk metallic glasses with crystalline in-situ precipitates (â phase) has been constructed from high temperature phase information, chemical composition analysis, and â phase crystallization kinetics. The phase evolution was detected in-situ by high energy synchrotron X-ray, and kinetic information on crystalline phase was measured from electrostatic levitation facility (ESL). This processing map offers a unique opportunity to control both volume and size of the dendritic â phase through composition and processing condition manipulation. The volume fraction of â phase can be customized from 6% to 93 %, and dendrite size is controllable between 1 and 50 µm at the current stage.
Comprehensive Mechanical and Tribological Characterization of Ultra-Thin-Films
Authors: Gitis Norm , Vinogradov Michael , Hermann Ilja , Kuiry Suresh 
Published: April 2011

AbstractBased on recent studies, mechanical and tribological properties such as hardness, Young's modulus, friction, and scratch adhesion strength on various coatings and ultra-thin films are reported. These results were obtained using a Universal Nano+Micro Tester UNMT-1, suitably designed for comprehensive evaluation of mechanical and tribological properties of bulk materials, coatings and thin films. Results indicate that a substrate effect for ultra-thin films is substantial when using conventional static nanoindentation technique, while negligible with an advanced dynamic nano-indentation. Comparative results of hardness and Young's modulus obtained from various techniques are presented. Also, a means to evaluate friction and adhesion strength of thin films is highlighted, using DLC specimens as an example.
Microstructure and Mechanical Properties Characterisation of Nanocrystalline Copper Films
Authors: Tjahyono Nursiani Indah , Chiu Yu Lung 
Published: April 2011

AbstractThe microstructure and mechanical properties of nanocrystalline copper with grain size ranging from 50 nm to 80 nm have been investigated. Thin films of nanocrystalline copper were electrodeposited from an additive-free acidified copper sulphate solution at room temperature by employing constant current at different current density magnitudes between 20 and 80 mA/cm2. Both austenitic and ferritic steel substrates with the same surface finishing conditions have been used for the deposition. The microstructure of the thin films has been further studied using electron microscopy techniques, and the mechanical properties using nanoindentation technique. The nanoindentation study was carried out on both the plan view and cross-sectional directions to study the isotropy characteristic of the copper film. It has been noted that both the modulus and hardness measured following the Oliver-Pharr scheme show an apparent indentation size effect tested on the cross-sectional sample.
An algorithm to determine the plastic properties of materials based on the loading data in single sharp indentation
Authors: Yonezu Akio , Hirakata Hiroyuki , Minoshima Kohji 
Published: April 2011

AbstractWe proposed a method to determine the plastic properties of bulk materials based on data of loading curvature in indentation curve with only one sharp indenter. This method uses the dimensional analysis to solve the representative stress and effective yield stress. Indentation unloading data is only used to select the unique solution from the calculated ones obtained from representative stress and effective yield stress. We applied the proposed method to four engineering metals on an experimental basis, to verify its effectiveness, as well as its superiority to the reported methods.
Quasi-static and Oscillatory Indentation in Linear Viscoelastic Solids
Authors: Cheng Yang-Tse , Cheng Che-Min 
Published: April 2011

AbstractInstrumented indentation is often used in the study of small-scale mechanical behavior of “soft” matters that exhibit viscoelastic behavior. A number of techniques have been used to obtain the viscoelastic properties from quasi-static or oscillatory indentations. This paper summarizes our recent findings from modeling indentation in linear viscoelastic solids. These results may help improve methods of measuring viscoelastic properties using instrumented indentation techniques.
Uniaxial Compression Behavior of Bulk Nano-twinned Gold from Molecular Dynamics Simulation
Authors: Deng Chuang , Sansoz Frederic 
Published: April 2011

AbstractParallel molecular dynamics simulations were used to study the influence of pre-existing growth twin boundaries on the slip activity of bulk gold under uniaxial compression. The simulations were performed on a 3D, fully periodic simulation box at 300 K with a constant strain rate of 4×107 s−1. Different twin boundary interspacings from 2 nm to 16 nm were investigated. The strength of bulk nano-twinned gold was found to increase as the twin interspacing was decreased. However, strengthening effects related to the twin size were less significant in bulk gold than in gold nanopillars. The atomic analysis of deformation modes at the twin boundary/slip intersection suggested that the mechanisms of interfacial plasticity in nano-twinned gold were different between bulk and nanopillar geometries.