bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Inkjet Deposition of Ceramic Green Bodies: II – Jet Behaviour and Deposit Formation
Authors: Reis N. , Seerden K. A. M. , Derby B. , Halloran J. W. , Evans J. R. G. 
Published: April 2011

AbstractIn order to successfully build three-dimensional shapes by hot-melt inkjet deposition it is essential to control the building block characteristics, i.e., the deposit geometry, dimensions and fine feature resolution. The deposit formation is mainly dependent on the material systems and their jetting behaviour. It is therefore crucial to understand how the jet formation is affected by the inks 'rheological properties and how to manipulate the jet-head driving parameters to achieve optimum deposition conditions. This paper reports our investigations with a model jet firing station, about the influence of driving parameters of hot-melt drop-on-demand print-heads (e.g., pulse shape and frequency) on the jet and deposit formation characteristics, for both unfilled and powder loaded vehicles.
Three Dimensional Microstructures from Metal Carbonyls
Authors: Lind Jan-Erik , Nyrhila Olli , Kotila Juha , Syvanen Tatu 
Published: April 2011

Abstract3D-LCVD of nickel and iron carbonyls was studied in order to grow 3-D metal forms under static or scanning Nd:YAG-laser beam. In addition to growth, emphasis was also placed on the prevention of the simultaneous decomposition of carbon monoxide, which interferes with the metal growth process. This was essential, because the fairly high precursor gas pressures of the metal carbonyls are very tempting for the 3D-LCVD. Parameters to be optimized included precursor pressure, laser power, laser scan speed and spot size. In order to optimize the growth parameters, the microstructures of the resulting forms were studied using SEM. Comparison between static and scanning growth is presented with the building philosophy in mind, e.g. whether to build structures layer by layer, from modules or in conjunction with another process to compensate for their shortcomings. The substrates used included steel, graphite and porous bronze.The results indicated different microstructures for iron and nickel, which were dependent on the total/precursor pressure. In the scanning experiments, nickel produced very thin films of high reflectivity, whereas iron produced a structure which could be described as a crystalline spider's web. The static experiments produced solid rods in the case of nickel, whereas with iron, the rods were hollow, even with same spot sizes. Moreover, an evident change in the microstructure of the nickel forms as a function of pressure was observed. The 3-D growth rate of the static experiments seemed very promising for the forthcoming scanning experiments.
Solid Freeform Fabrication of Silicon Nitride Ceramics
Authors: Gasdaska C. J. , Clancy R. , Jamalabad V. , Dalfonzo D. 
Published: April 2011

AbstractSilicon nitride ceramics have been prepared using the fused deposition (FD) process in a Stratasys 1650 modeler. Two types of silicon nitride have been prepared: GS44 and AS800. AS800 is processed and used at higher temperatures than GS44. The strength of machined surfaces of either type of silicon nitride prepared using FD is comparable to conventionally processed material. Using standard build conditions strengths for as-built and as-sintered
surfaces are approximately 50% lower. The additive nature of solid freeform processes also allows multi-material combinations to be deposited which result in enhanced performance. For example, combinations of silicon nitride based materials with different thermal expansion coefficients have been prepared which demonstrate strength increases > 20%. In addition, components containing complicated internal cavities may also be fabricated.
Thermoelectric Properties of the Cubic Family of Compounds AgPbBiQ3(Q = S, Se, Te). Very Low Thermal Conductivity Materials
Authors: Sportouch S. , Basteat M. , Brazis P. , Ireland J. , Kannewurf C. R. , Uher C. , Kanatzidis M. G. 
Published: April 2011

AbstractThe AgPbBiQ3class of compounds and their solid solution members are related to the NaCl structure type, where Ag, Pb and Bi atoms are statistically disordered on the Na site and Q atoms occupy the Cl site. These compounds were synthesized by combining the elements in the appropriate ratio and heating under static vacuum at 900° C for 3 days. They are narrow gap semiconductors with band gaps in the range of 0.6 to 0.28 eV. The charge-transport properties were measured on ingots as a function of temperature. The compounds AgPbBiTe3, AgPbBiSe3, AgPbBiTe2.75Se0.25and AgPbBiTe2Se, undoped, possess an electrical conductivity in the range of 70 S/cm to 400 S/cm. These materials exhibit negative thermopower ranging from -40 μV/K to -160 μV/K at room temperature and thermal conductivity less than 1.30 W/mK.
High Temperature Transport Probe for Thermopower and Resistmty Measurements
Authors: Littleton R. T. , Jeffries Jason , Kaeser Michael A. , Long Michael , Tritt Terry M. 
Published: April 2011

AbstractWe have recently developed a device to measure resistivity and Seebeck values of a material as a function of temperature over a range of 80K < T < 700K. These measurements overlap in temperature with our existing apparatus (4K < T < 320K). These measurements are necessary for the investigation of potential thermoelectric materials at elevated temperatures, where power generation applications are important. The probe design allows for various types of samples to be evaluated from needle like samples ( L ≈ 2mm, D ≈ 50μm ) to larger pressed pellet samples ( ≈ 2mm × 2mm × 10mm). Separate high temperature cartridge heaters are used to stabilize both the absolute temperature, T, as well as the temperature difference, ΔT. Thermocouples measuring T+ΔT/2 and T-ΔT/2 are also employed to measure sample voltages for resistance and thermoelectric power. Design details and measurement specifics will be discussed. Data taken on standards a well as some research samples will be presented.
Fabrication of Thermoelectric Modules Using Thermoelectric Pastes and an Additive Technology
Authors: Xi Xiaomei , Matijasevic Goran , Ha Linh , Baxter Dan 
Published: April 2011

AbstractPolymer based thermoelectric pastes have been developed by dispersing metal and metal alloy powders into a polymer binder system. Thermoelectric materials and elements are formed by depositing the pastes into a mold or onto a substrate and subsequently sintering them to form a conductive network with thermoelectric properties. A Seebeck coefficient of 65 μV/°K, and a resistivity of 0.05 Ω-cm have been achieved in the early stage of material development. A novel processing method has also been developed for the fabrication of small size thermoelectric elements and thermoelectric modules with a multitude of thermoelectric couples using these pastes. Thermoelectric elements as small as 250 μm in diameter and 25 μm in thickness have been achieved. Thermoelectric modules with 275 couples/in2have been fabricated using the thermoelectric pastes and the fabrication technique. Further improvement in the material properties and reduction in the sizes of the thermoelectric elements are underway.
Electrical Properties of Orthorhombic Iron Disilicide
Authors: Tani Jun-Ichi , Kido Hiroyasu 
Published: April 2011

AbstractIn order to clarify the electrical properties of Cr-doped β-FeSi2(Fe1-xCrxSi2) and Mn-doped β--FeSi2(Fel-yMnySi2), the Hall effect and electrical resistivity of Fe1-xCrxSi2(0.01 ≦ x ≦ 0.05) and Fel-yMnySi2(0.01 ≦ y ≦ 0.10) have been measured in the temperature range between 80 and 300 K. fhe solid solutions Fel-xCrxSi2and Fel-yMnySi2are p-type over the measured temperature range. The observed features of RH of these solid solutions are explained by using the two-band model with the existence of two acceptor levels. The hole concentration of Fe1-xCrxSi2at 300 K ranges from 8.9×1018cm−3for x=0.01 to 1.1×1020cm−3for x=0.05, which is one order of magnitude higher than that of Fel-yMnySi2.
Thermoelectric Bismuth Wire Array Composites
Authors: Huber T. E. , Graf M. J. , Foss C. A 
Published: April 2011

AbstractThe resistance R of a high density array of 200 nm diameter wires in anodic alumina is studied experimentally. R decreases from 300 K down to 0.3 K. An anomalous drop in R was found at T<50 K. Possible explanations are considered, including one based on the onedimensional quantum size effect. Also, the large magnetoresistance is suggestive of weaklocalization effects. The implication for the thermoelectric properties is discussed.
Electronic Structure of Complex Bismuth Chalcogenides and Other Narrow-Gap Thermoelectric Materials
Authors: Mahanti S. D. , Larson P. , Chung Duck-Young , Sportouch S. , Kanatzidis M. G. 
Published: April 2011

AbstractThere is considerable current effort to discover new thermoelectric materials with a high figure of merit Z. Some of these new materials are narrow-gap semiconductors with rather complex crystal structures. In this paper we discuss the results of electronic structure calculations in two classes of such systems. The first class consists of BaBiTe3, a structural and chemical derivative of the well-studied Bi2Te3. Similarities and differences in the band structures of these two systems are discussed. The second class consists of half-Heusler or “stuffed”-NaCl compounds MNiX, where M is Y, La, Lu, Yb, and X is a pnictogen; As, Sb, Bi. To understand the physical reason behind the energy gap formation, we compare the electronic structure of YNiSb with that of an isoelectronic system ZrNiSn, another isostructural compound of thermoelectric interest. These calculations were carried out within density functional theory (in generalized gradient approximation) using self-consistent full-potential LAPW method. Energy gaps and effective masses associated with the conduction band minimum and valence band maximum have been calculated and these quantities have been used to estimate transport properties. Large room temperature thermopower values in Bi2Te3 and BaBiTe3 can be understood in terms of multiple conduction and valence band extrema whereas similar large values in ZrNiSn and other half-Heusler compounds can be ascribed to large electron and hole effective mass.
Materials With Open Crystal Structure as Prospective Novel Thermoelectrics
Authors: Uher Ctirad , Yang Jihui , Hu Siqing 
Published: April 2011

AbstractA useful approach to identify materials with high thermoelectric figure of merit is to search for solids that offer great flexibility to modify and tailor the structure so as to achieve the optimal transport behavior. Among the most promising novel thermoelectric materials are solids with “open crystal structure”. They may be typified by structures with unfilled cages, crystals with an empty atomic sublattice, and by a network of polyhedral cages enclosing guest species. In this paper we present our latest results concerning transport properties in the above classes of solids. Specifically, we focus on the filled skutterudites, half-Heusler alloys, and clathrates.
Materials Development for Thermomagnetic Cooling
Authors: Freibert F. , Migliori A. , Darling T. W. , Trugman S. A. 
Published: April 2011

AbstractWe review thermoelectric effects in a magnetic field at a phenomenological level. The measurement problem is discussed in detail, and results are presented based on the time-dependent voltages developed by thermoelectric materials in zero field and in large magnetic fields. These time dependent voltages provide a direct and unambiguously accurate measurement of both the Peltier and Ettingshausen figures of merit, and can be used to obtain all the relevant transport including thermal conductivity. Discussion of the limiting performance of both Peltier and Ettingshausen coolers are discussed. Data are shown for Ettingshausen materials with part-per-million levels of Sn doping. Thought these materials exhibit high Ettingshausen figures of merit, Sn doping does not appear to improve performance.
Thermoelectric Properties of Cr3S4-Type Selenides
Authors: Snyder G. Jeffrey , Caillat T. , Fleurial J. -P. 
Published: April 2011

AbstractSeveral compounds with the Cr3S4 structure type have been studied for their thermoelectric properties. All exhibit low lattice thermal conductivity of about 15 mW/cmK, independent of temperature. Many of the compounds, such as Co3Se4, Ni3Se4, Fe3Se4, Ti3Se4, FeNi2Se4, and FeCo2Se4, are metals with relatively low electrical resistivity and Seebeck coefficient. The Cr containing compounds, such as Cr3Se4, NiCr2Se4, CoCr2Se4, and FeCr2Se4, have the largest Seebeck coefficients and highest resistivity. thermoelectric applications is FeCr2Se4.
The Synthesis of Metastable Skutierudites Using Superlattice Reactants
Authors: Sellinschegg Heike , Williams Joshua R. , Casperson Julie , Nolas George , Johnson David C. 
Published: April 2011

AbstractThe synthesis by controlled crystallization of elementally modulated reactants of a series of kinetically stable, crystalline skutterudites (M′1−xM4Sb12 where M′ = vacancy, RE, Hf, Al, Sn, Pb, Bi, In, Ga, Al and Y; M = Fe, Co) is discussed. Low angle diffraction data demonstrates that the elemental layers interdiffuse at temperatures below 150°C. Nucleation of the skutterudite structure occurs exothermically on annealing at temperatures near 200°C regardless of the ternary metal. The metastable ternary compounds and the new binary compound were found to decompose exothermically on higher temperature annealing. The decomposition temperature ranged from 300°C for the binary compound FeSb3 to 550°C for Eu′1−x;Fe4Sb12 to higher temperatures for the filled cobalt end members. The occupation of the lattice site for the ternary cation was found to depend on the composition of the initial reactant. Samples up to a half gram in size have been synthesized and hot-pressed into pellets for measurement of both electrical properties and thermal conductivity. Preliminary evidence is presented for the formation of skutterudite superlattices, again synthesized by the controlled crystallization of elementally modulated reactants.
Thermoelectric Properties of Two Ternary Tellurides
Authors: Sharp Jeff W. , Sales Brian C. , Mandrus David G. , Chakoumakos Bryan C. 
Published: April 2011

AbstractWe present initial assessments of the thermoelectric properties of two ternary tellurides with known crystal structures, Tl2GeTeM5 and Tl2SnTe5. Tl2SnTe5 appears to have a p-type figure of merit about the same as that of Bi2Te3, the best thermoelectric material among binary compounds. A good figure of merit is possible because the lattice thermal conductivity is very low. Based on neutron diffraction data, we have calculated atomic displacement parameters and thermal expansion coefficients. The atomic displacement parameters give some understanding of the low lattice thermal conductivity.
Enhanced Thermionic Emission Cooling in High Barrier Superlattice Heterostructures
Authors: Shakouri Ali , LaBounty Chris , Abraham Patrick , Piprek Joachim , Bowers John E. 
Published: April 2011

AbstractThermionic emission current in heterostructures can be used to enhance thermoelectric properties beyond what can be achieved with conventional bulk materials. The Bandgap discontinuity at the junction between two materials is used to selectively emit hot electrons over a barrier layer from cathode to anode. This evaporative cooling can be optimized at various temperatures by adjusting the barrier height and thickness. Theoretical and experimental results for nonisothermal thermionic emission in heterostructures are presented. Single stage InGaAsP-based heterostructure integrated thermionic (HIT) coolers are fabricated and characterized. Cooling on the order of a degree over one micron thick barriers has been observed. Nonisothermal transport in highly doped tall barrier superlattices is also investigated. An order of magnitude improvement in cooling efficiency is predicted for InAlAs/InP superlattices.
Analysis of Antimony-Tin-Based Skutterudites
Authors: Schujman S. B. , Slack G. A. , Nguyen H. C. , Nolas G. S. , Young R. A. , Mohammed F. , Tritt T. 
Published: April 2011

AbstractSince the proposal of skutterudites as possible Phonon-Glass, Electron-Crystal materials, a lot of work has been done trying to fill the structural voids with foreign “rattling” atoms. In order to keep the electronic count per unit cell constant (and thus, the semiconducting properties of most of the compounds under study) partial replacement of either the cation or the anion in the original formula by an appropriate neighbor in the periodic table is an option. In the case of antimonides, replacing part of the Sb with Ge or Sn in order to compensate the extra charge introduced by void fillers has proved useful for compounds based on rare-earth filled IrSb3. In the case of RhSb3, we found that large quantities of Sn can be incorporated into the skutterudite structure of RhSb3 without either filling the voids or producing charge carriers.We have analyzed the stability of several cross-sections of the Rh-Sb-Sn ternary system and have found a wide range of compositions with the basic skutterudite structure as we vary the Sn content. In all the cases, the tin goes substitutionally into the antimony sites. The voids remain empty. Density measurements suggest the existence of metal vacancies, confirmed by Rietveld refinement of the powder X-ray diffraction patterns. The possibility of Sn-induced mixed-valence of Rh on the anion sites is being investigated.
Microstructure and Thermoelectric Properties of Thin Foils of Bismuth Telluride Alloys
Authors: Koukharenko E. , Frety N. , Shepelevich V. G. , Tedenac J. C. 
Published: April 2011

AbstractUltrarapid quenching processes have been extensively studied during the past few years. particularly for glasses. In the case of polycrystalline materials, the problem is slightly different. In this case, the microstructures obtained by this process are very different from those obtained by normal cooling and they induce new physical properties.
Transport Properties Of Doped CsBi4Te6 Thermoelectric Materials
Authors: Brazis Paul W. , Rocci Melissa , Chung Duck-Young , Kanatzidis Mercouri G. , Kannewurf Carl R. 
Published: April 2011

AbstractIn previous investigations we have introduced a variety of new chalcogenide-based materials with promising properties for thermoelectric applications. The chalcogenide CsBi4Te6 was previously reported to have a high ZT product with a maximum value at 260K. In order to improve this value, a series of doped CsBi4Te6 samples has been synthesized. Current doping studies have been very encouraging, with one sample found to have a maximum power factor of 51.5 μW/cm·K2 at 184 K. This paper reports on material characterization studies through the usual transport measurements to determine optimum doping concentration for various dopants.
Theoretical Modeling of Thermoelectricity in Bi Nanowires
Authors: Sun X. , Zhang Z. , Dresselhaus G. , Dresselhaus M. S. , Ying J. Y. , Chen G. 
Published: April 2011

AbstractBismuth as a semimetal is not a good thermoelectric material in bulk form because of the approximate cancellation between the electron and hole contributions. However, quantum confinement can be introduced by making Bi nanowires to move the lowest conduction subband edge up and the highest valence subband edge down to get a one-dimensional (1D) semiconductor at some critical wire diameter dc. A theoretical model based on the basic band structure of bulk Bi is developed to predict the dependence of these quantities on wire diameter and on the crystalline orientation of the bismuth nanowires. Numerical modeling is performed for trigonal, binary and bisectrix crystal orientations. By carefully tailoring the Bi wire diameter and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire diameters.
Understanding and Tailoring the Mechanical Properties of Liga Fabricated Materials
Authors: Buchheit T. E , Christenson T. R. , Schmale D. T. , Lavan D. A. 
Published: April 2011

AbstractLIGA fabricated materials and components exhibit several processing issues affecting their metallurgical and mechanical properties, potentially limiting their usefulness for MEMS applications. For example, LIGA processing by metal electrodeposition is very sensitive to deposition conditions which causes significant processing lot variations of mechanical and metallurgical properties. Furthermore, the process produces a material with a highly textured lenticular microstructural morphology suggesting an anisotropic material response. Understanding and controlling out-of-plane anisotropy is desirable for LIGA components designed for out-of-plane flexures. Previous work by the current authors [6] focussed on results from a miniature servo-hydraulic mechanical test frame constructed for characterizing LIGA materials. Those results demonstrated microstructural and mechanical properties dependencies with plating bath current density in LIGA fabricated nickel (LIGA Ni). This presentation builds on that work and fosters a methodology for controlling the properties of LIGA fabricated materials through processing. New results include measurement of mechanical properties of LIGA fabricated copper (LIGA Cu), out-of-planeand localized mechanical property measurements using compression testing and nanoindentation of LIGA Ni and LIGA Cu.
Shape Memory and Magnetostrictive Materials for Mems
Authors: Wuttig Manfred , Quandt Eckhard , Ludwig Alfred , Winzek Bernhard 
Published: April 2011

AbstractFerroic materials are ideally suited for actuators in MEMS applications. Ferro- elastic materials, i.e. shape memory alloys (SMAs), produce a significant, o. o. 104 microstrain, phase transformation induced thermoelastic eigenstrain. Rare earth based ferromagnetic materials possess large, o.o. 103 microstrain, saturation magnetostriction which can be developed at fields of the order of mT readily achieved in MEMS geometries. This paper discusses the essentials of the thermoelastic stress evolution in SMA/Substrate bimorphs and of the development of rare earth based ferromagnetic multilayers. SMA actuationunder the constraint of a substrate and the optimization of the multilayers are emphazized.
Dc Magnetron Reactive Sputtering of Low Stress Ain Piezoelectric Thin Films for Mems Application
Authors: Hsieh Peter , Reif Rafael , Cunningham Brian 
Published: April 2011

AbstractMany MEMS devices require piezoelectric excitation and readout to actuate and sense motion of mechanical structures. Aluminum nitride is advantageous for MEMS fabrication because it is compatible with silicon integrated circuit foundry impurity contamination requirements, can be deposited at low temperatures, provides a high piezoelectric coefficient, and is easily patterned using conventional photolithographic techniques. In this work, AIN thin films were deposited on silicon substrates for use in a MEMS silicon membrane ultrasonic resonator. The ultrasonic resonator is configured as a gravimetric sensing device for chemical detection. Issues of concern with regard to device performance and yield include the maximization of the electromechanical coupling constant (k2), film stress control, and film uniformity; these issues were addressed through a central composite design set of experiments to resolve the film property responses as a function of the deposition parameters. Film characterization was conducted with x-ray diffraction, spectroscopic ellipsometry, and surface profilometry. Optimization of film deposition parameters improved sensor performance and enabled further device miniaturization with the use of thinner films.