bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maximum pore volume fraction and size for high fracture energy in porous bodies
Authors: Vandeperre Luc J. , Wang Jiaping , Clegg William J. 
Published: April 2011

ABSTRACTThe fracture energy of a body containing pores might be expected to decrease linearly in proportion to the area fraction of material in the crack plane. However, there is experimental evidence that the fracture energy of porous materials only decreases when the pore volume fraction exceeds some critical value. To understand this, experiments have been conducted to directly observe the interaction between a growing crack with model distributions of pores. It is seen that cracks do not simply pass through the pores but spread around them causing the crack front to become curved and increase in length. For just two pores (or a line of pores) this is observed to continue until the crack has completely spread around the pores. It is observed that this increase in length increases the energy required for cracking, suggesting that the maximum fracture energy should rise with the volume fraction of pores. However, when this exceeds a certain value, the spreading crack front impinges on the pores ahead of the crack front before the maximum length of crack front due to bowing is reached. Beyond this critical volume of porosity, the resistance to fracture drops rapidly with porosity. Predictions of the relative fracture resistance of bodies containing spherical as well as cylindrical pores give good agreement with experimental observations, and are consistent with observations that the matrix fracture energy and pore size have little effect, provided the pores are much smaller than the sample.
Studies of residual stress, microcracks, hardness and microstructure of cold compacted metallic green bodies
Authors: Ericsson Torsten , Larsson Cecilia , Peng Ru Lin 
Published: April 2011

ABSTRACTThe residual stresses have been measured by X-ray and neutron diffraction on PM green bodies manufactured by conventional and high speed compaction of iron powder with and without added copper and brass powder. Compressive residual stresses are present in a thin layer in both top and side surfaces. They are largest in the side surfaces due to plastic deformation of the surface material caused by the friction forces during ejection out of the die. In the interior of the green body residual stresses exist with certain region under compression (periferical regions) and other under tension (more central regions). It is unclear whether mixing iron powder with brass or copper powder leads to considerable phase stresses between the two phases.
Size and Density Separation in Granular Materials
Authors: MöBius Matthias , Nagel Sidney R. , Jaeger Heinrich M. 
Published: April 2011

ABSTRACTWe review mechanisms leading to the separation of granular mixtures according to the size or density of the constituent particles. Besides a general overview, the focus of this article is on separation induced by vertical vibrations of the vessel holding the granular material, and specifically on recent results showing a density-dependence to the separation process. A convenient measure of the separation speed is the rise time of a larger “intruder particle” from some fixed initial depth to the free surface, where it will remain. Recent experiments have shown that for large intruder sizes the rise time depends on the density of the intruder particle. Furthermore, in three-dimensional systems we found that this density dependence is highly nonmonotonic. While there is no detailed theoretical understanding available yet, our experiments demonstrate that this surprising behavior is produced by interactions not only between the large intruder particle and the smaller particles of the surrounding granular bed, but also between the particles and the interstitial air.
The New Materials Science and Engineering Curriculum at the Ohio State University
Authors: Gupta P. K. , Anderson P. M. , Buchheit R. G. , Dregia S. A. , Lannutti J. J. , Mills M. J. , Snyder R. L. 
Published: April 2011

ABSTRACTA new Materials Science and Engineering (MSE) curriculum is in effect at the Ohio State University starting fall, 2002. This curriculum is composed of four parts:1) General Education Core (required by the University of all undergraduates).2) Engineering Core (required by the College of Engineering). This includes courses in English, Math, Physics, Chemistry, Statistics, Programming, Statics, and Stress Analysis.3) Materials Science and Engineering Core (required by the MSE Department). It includes courses on Atomic Scale Structure, Microstructure and Characterization, Mechanical Behavior, Electrical Properties, Thermodynamics, Transport and Kinetics, Phase Diagrams, Phase Transformations, Modeling of Material Processes, Materials Selection, and Materials Performance).4) MSE-Specialization in the senior year (required by the MSE Department). Novel features of the new curriculum include:1) concentration in a specialized area of MSE in the senior year.2) increased exposure to MSE courses in the second year.3) increased industrial exposure.4) redesigned laboratory courses.
An Upper Division General Education Course on Materials for Non-Engineering Students
Authors: Bahr D. F. , Norton M. G. 
Published: April 2011

ABSTRACTWe present the structure of a new course which is designed to expose junior and senior level undergraduates in non-engineering fields to materials. Washington State University has a “General Education” requirement, which requires students to take a variety of courses including the area of sciences, humanities, and technology. We have developed this course to satisfy the requirement for technology for upper division students. The results of the enrollment over the past 3 years are presented: each semester more majors are taking the course, suggesting it is reaching an multidisciplinary audience. Comments from the students and plans for the future are discussed.
An Organic FET structure for unconventional substrates
Authors: Bonfiglio Annalisa , Mameli Fulvia , Sanna Ornella , Lutsen Laurence 
Published: April 2011

ABSTRACTA structure for organic TFTs suitable for being transferred on unusual substrates is described in each technological step. The proposed device consists in a “bottom-structure” assembled on a flexible and transparent insulating layer, without any substrate, with source and drain contacts on one side and the gate on the opposite side. The main advantage is to avoid the substrate because the insulator itself is able to support the whole structure. For this reason, application to any kind of substrates after the built-in process is possible.
A Protein Patterning Technique And Its Application In Bio-Inspired Self-Assembly
Authors: Guo D. , McNally H. , Pingle M. , Bergstrom D. , Bashir R. 
Published: April 2011

ABSTRACTProtein patterning techniques are crucial for the development of antibody-based biosensor and the study of controlled cell growth. This paper discusses a protein patterning technique based on microelectronic fabrication, DNA hybridization and biotin-streptavidin pair. A gold-on-silicon-dioxide substrate with micron size pattern was fabricated with photolithography and lift-off process. The average surface roughness of the gold pattern is 4.3 nm, measured by contact mode AFM. Thiol derivatized single stranded DNA was attached to the gold pattern surface by the chemical bonding between gold atom and sulfur atom. Surface attached DNA was then hybridized with a biotin conjugated complementary DNA sequence. Thus, the gold pattern was translated into a biotin pattern with similar resolution. Fluorescein conjugated streptavidin was patterned as demonstration. Fluorescence microscopy shows relative uniform streptavidin coverage of micron resolution and low background non-specific binding. The proposed protein patterning technique takes advantage of the high resolution of modern microelectronic fabrication. It has the potential of reaching sub-micron resolution. The biotin-streptavidin pair provides extremely specific and stable linking for protein immobilization. To show its application in biological inspired self-assembly, this technique was used successfully in the self-assembly of 20 nm streptavidin conjugated gold particles.
Self-aligned Split Gate Electrodes Fabricated on Suspended Carbon Nanotubes
Authors: Lee S.-B. , Robinson L. A. W. , Teo K. B. K. , Chhowalla M. , Amaratunga G. A. J. , Milne W. I. , Hasko D. G. , Ahmed H. 
Published: April 2011

ABSTRACTWe describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.
Material Issues of Low Temperature Co-fired Ceramic (LTCC) Fine Pitch Chip Scale Package (CSP) Designs
Authors: Owens Megan M. , Soucy Joseph W. , Marinis Thomas F. , Bruff Kevin A. , Clausen Henry G. 
Published: April 2011

ABSTRACTLTCC substrates for fine pitch (1.0 mm and 0.8 mm) CSP applications have been designed, fabricated, and assembled. The assembly process, including ball grid array (BGA) solder ball attach, die mount, wire bond, and glob top is described. The material and physical design interaction issues that emerged during development are discussed.The initial CSP design was conventional, with co-fired yellow gold (Au) vias and capture pads and post-fired solderable gold (PtPdAu) pads for solder ball attachment. Because LTCC tape shrinks during co-fire, solder pads were applied post co-fire to ensure proper mating with existing test fixtures and to provide the best alignment relative to the CSP body. Solder pad to capture pad misalignment was visible following solder pad firing. After CSP attachment to a test board, electrical tests revealed opens. Investigation led to the following conclusions. The decreased solder pad diameter necessary to accommodate the fine pitch design was significant relative to the area allocated for the underlying via and capture pad. Misalignment that would have been hidden under larger solder pads was exposed. Even when the capture pad surface was not visibly exposed, the offset solder pad meant less material between the capture pad and the solder ball, less of a barrier to solder leaching. Solder leaching into the yellow gold, observed after CSP removal from the test board, was the cause of the electrical disconnects. In the second design, the capture pad was eliminated in order to discourage leaching by reducing the volume of yellow gold available to alloy with the solder pad during co-fire. Reflow operations still resulted in leached solder pads. A third design replaced the first-layer via yellow gold with a solderable gold. This design proved to be robust.While developing designs and fabricating these prototypes, it was noted that all ball failures consistently occurred between the solder pad and the LTCC substrate. To investigate adhesion using different metallizations, shear tests were performed on LTCC substrates with either post-fired solder pads or co-fired pads. To investigate how the substrate material affects adhesion, alumina CSPs were also sheared. Shear test results are presented.
In-Plane Ferroelectricity in Strontium Titanate Thin Films
Authors: Astafiev K. F. , Sherman V. O. , Cantoni M. , Tagantsev A. K. , Setter N. , Petrov P. K. , Kaydanova T. , Ginley D. S. 
Published: April 2011

ABSTRACTThe results of structural and electrical characterizations of SrTiO3 thin films deposited onto LaAlO3 substrates by pulsed laser deposition technique are presented. The appearance of the ferroelectric phase in these films has been experimentally documented, the transition temperature being in the range of 90–120K. The hysteresis loops have been monitored in a wide temperature range by using thin film planar capacitors, the driving field being predominantly in the plane of the film. The switching properties of the films has been studied at low temperatures (∼25K) and well saturated loops have been observed with relatively low coercive field (<6kV/cm for 10μm gap). The presence of the imprint phenomenon has been also found at low temperatures.The microstructure of the investigated SrTiO3 thin films has been studied by using a high resolution transmission electron microscope (TEM). It has been found that the annealed and as-deposited thin films, being of the same composition, have quite different microstructures. The difference observed in the polarization response of the films is related to that in their microstructure.
Theoretical and Experimental Study of Barium Zinc-Cadmium Tantalate-based Microwave Dielectrics
Authors: Liu Shaojun , Van Schilfgaarde Mark , Sun Jian , Badd Louisa , Smith David , Petrovixc Novak S. , Taylor R. , Newman N. 
Published: April 2011

ABSTRACTSingle-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic was not formed from solid-state diffusion alone. The resulting Ba(Cd0.327Zn0.006Ta2/3)O3 material sintered at 1550° C exhibits a dielectric constant of ∼33 and loss tangent of <5×10−5 at 2 GHz. In our more recent work, we have used boron as a sintering aid to facilitate sintering at temperatures as low as 1300° C, enhance the structural quality and improve the microwave properties of Ba(Cd1/3Ta2/3)O3 dielectrics. TEM results indicate that the liquid sintering mechanism is an important factor for boron concentrations exceeding 0.5wt%, while a point defect mechanism plays the dominant role at lower boron concentrations. The presence of superstructure peaks and splitting of the (220) and (214) peaks in X-ray diffraction spectra are direct evidence for the distortion from cubic symmetry as a result of Cd and Ta ordering on the B-site.Ab-initio electronic structure calculations within the local density functional approximation have been used to give insight into the unusual properties of this class of materials. In both Ba(Zn1/3Ta2/3)O3 and Ba(Cd/3Ta2/3)O3, the conduction band maximum and valence band minimum are composed of mostly weakly itinerant Ta 5d-and Zn-3d/Cd-4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and possibly inherently lower intrinsic microwave loss than comparable ionic materials.
A New Dielectric Material System of xLa(Mg1/2Ti1/2) O3−(1−X) CaTiO3 at Microvave Frequency
Authors: Chen Yuan-Bin , Huang Cheng-Liang , Row Che-Win 
Published: April 2011

ABSTRACTThe dielectric properties and the microstructures of xLa(Mg1/2Ti1/2)O3−(1−x)CaTiO3 ceramics with B2O3 additions (0.25wt%) prepared with conventional solid-state route have been investigated. Doping with B2O3 (0.25wt%) can effectively promote the densification and the dielectric properties of xLa(Mg1/2Ti1/2)O3−(1−x)CaTiO3 ceramics. It is found that xLa(Mg1/2Ti1/2)O3−(1−x)CaTiO3 ceramics can be sintered at 1400°C due to the liquid phase effect of B2O3 addition observed by Scanning Electronic Microscopy. At 1425°C, 0.5La(Mg1/2Ti1/2)O3−0.5CaTiO3 ceramics with 0.25 wt% B2O3 addition possesses a dielectric constant (εr) of 43, a Q×f value of 24470 (at 8GHz) and a temperature coefficients of resonant frequency (τf) of -8.94 ppm/°C. As an increasing the content of La(Mg1/2Ti1/2)O3, the highest Q×f value of 30824(GHz) could be achieved for X=0.7.
Rapid Prototype Fabrication of Custom Chip Scale Packages
Authors: Owens Megan M. , Soucy Joseph W. , Marinis Thomas F. , Clausen Henry G. 
Published: April 2011

ABSTRACTMany new electronic systems require very high-density packaging to meet system volume and weight constraints. The Chip Scale Package (CSP) is often used to meet this need. However, the limited commercial availability of die in CSP form frequently drives system designers to pursue custom CSP fabrication. Long lead times and manufacturers' reluctance to run small batches typically limit the use of custom CSPs to high volume applications. This paper presents an approach for the rapid prototype of Low Temperature Co-fired Ceramic (LTCC) CSPs.Integral to the approach is the concept of using a small family of generic substrate designs to build a large variety of CSPs. The generic substrates may be fabricated and kept on hand until a CSP application need arises. When it does, a 12-to-16-week industry-typical lead time does not apply; the CSP may be fabricated rapidly, on site. Fabrication consists of simply singulating the substrate, populating the solder ball pads, mounting and wire bonding the die, encapsulating the substrate surface, and laser marking the assembly. The lead time may be slashed from several months to just a few days.The family of substrate designs will be described. The substrates, with gold-based interconnects, have standard JEDEC Ball Grid Array (BGA) footprints of either 0.8 mm or 1.0 mm pitch. Substrates have a top surface metallization scheme of either a large central die bond pad surrounded by a number of peripheral bond sites for wire bonds, or a blanket metallization layer that may be patterned, via photolithography, to accommodate a specific application at the time of need. The die pad design is used for CSPs with a single die, while the blanket metallization design is patterned for hybrid or multi-die applications. The design approach, custom photopatterning and gold etch, and assembly processes are presented.
Dielectric Properties of BaTiO3 Based Ceramics Prepared from Nano-powders
Authors: Wang Xiao-Hui , Chen Ren-Zheng , Gui Zhi-Lun , Li Long-Tu 
Published: April 2011

ABSTRACTIn this paper, the BaTiO3 nanoceramics have been fabricated by pressureless sintering for the first time. High purity BaTiO3 powders in nano-size of 50∼80nm synthesized by wet chemical method were used to fabricate nanoceramics. The addition of an appropriate amount of Nb2O5 and Co3O4 was found to suppress the grain growth, which is normally encountered in the conventional pressless sintering. The effects of Nb2O5 and Co3O4 on the phase structure, microstructure and dielectric properties of the sintered ceramics were investigated. The BaTiO3 ceramics with the average grain size less than 100nm were achieved after sintering below 1220°C with dielectric constant up to 2000 at room temperature, which is of cubic structure and meets the requirement of X7R specification.
High Electron Mobility SiGe/Si Transistor Structures on Sapphire Substrates
Authors: Alterovitz Samuel A. , Mueller Carl H. , Croke Edward T. , Ponchak George E. 
Published: April 2011

ABSTRACTSiGe/Si n-type modulation doped field effect structures and transistors (n-MODFETs) have been fabricated on r-plane sapphire substrates. The structures were deposited using molecular beam epitaxy, and antimony dopants were incorporated via a delta doping process. Secondary ion mass spectroscopy (SIMS) indicates that the peak antimony concentration was approximately 4×1019 cm−3. The electron mobility was over 1,200 and 13,000 cm2/V-sec at room temperature and 0.25 K, respectively. At these two temperatures, the electron carrier densities were 1.6 and 1.33×1012 cm−2, thus demonstrating that carrier confinement was excellent. Shubnikov-de Haas oscillations were observed at 0.25 K, thus confirming the two-dimensional nature of the carriers. Transistors, with gate lengths varying from 1 micron to 5 microns, were fabricated using these structures and dc characterization was performed at room temperature. The saturated drain current region extended over a wide source-to-drain voltage (VDS) range, with VDS knee voltages of approximately 0.5 V and increased leakage starting at voltages slightly higher than 4 V.
Integration of III-V Optoelectronic Components on Si Platform
Authors: Katsnelson Alex , Tokranov Vadim , Yakimov Michael , Oktyabrsky Serge 
Published: April 2011

ABSTRACTA method for hybrid integration of III-V optoelectronic components on Si substrate using BCB was demonstrated. The method included bonding, selective wet etching of the GaAs substrate, components separation by wet etching, two-level metallization and lateral oxidation to form optical apertures. Simulations of thermal behavior and mechanical stresses of this integration scheme were performed using finite element analysis, which revealed adequate heat dissipation. Simulations show that this bonding protocol allows reduction of overheating and mechanical stress that enhances the optoelectronic device performance and increases reliability. Electro-luminescence spectrum, I-V and P-T characteristics were measured and compared with a reference homoepitaxial structure and the results of the simulations. Measured thermal impedance was found to be less then two times higher than that for the devices on a host GaAs wafer. Novel method of substrate removal named oxidation lift-off was proposed and demonstrated. This process allows to release a VCSEL structure with epitaxial DBRs and separate individual components on Si, reduces the number of process steps and eventually reduces cost of the fabricated devices. Au/Ge alloy was used for the metal bonding of the test oxidation lift-off structure. Substrate removal, device separation, bonding and formation of the oxide apertures were done within a single processing step.
Site controlled nucleation of ferroelectric crystals: a step towards lithography modulated self-assembly
Authors: Muralt P. , Bühlmann S. , Von Allmen S. 
Published: April 2011

ABSTRACTAn additive technique for the growth of PZT crystallites in the sub-200 nm range on predefined sites is presented. The method is based on nucleation promotion by TiO2 seeds. Epitaxial (111)-oriented Pt on a SrTiO3 single crystal served as substrate. TiO2 seed sites have been defined by an e-beam lithographic process. The initial Pb flux determines whether (100) or (111) crystallites are obtained. Best results have been obtained with PZT(100) yielding one square grain per site with a narrow size distribution (120 to 150 nm). In this case, the seed collected additional PbO adatoms reaching the seed by diffusion. The sidewalls consist mostly of {110} facets. A model in the frame of classical nucleation theory describes well experimental observations. The piezoelectric response and the ferroelectric switching of the structures have been verified.
Preparation and Characterization of Ferroelectric Bi3TiNbO9-Bi4Ti3O12 (m =2–3) Thin Films with Different Superlattice Structures
Authors: Shibuya Akira , Noda Minoru , Okuyama Masanori 
Published: April 2011

ABSTRACTNatural-superlattice-structured Bi3TiNbO9–Bi4Ti3O12 (m =2–3) (BTN–BIT) films have been grown on Pt/TiO2/SiO2/Si substrates at 400 °C to 550 °C by pulsed laser deposition (PLD) using BTN–BIT (1 mol:1 mol) target, and were post-annealed in O2 for 45 minutes at 750 °C. BTN–BIT films prepared above 500 °C have single phase whose c lattice parameter is estimated to 8.300 nm in consideration of periodicity of lattice structures. This lattice constant is very close to the value (8.316 nm) of that of two unit cells of BTN and one unit cell of BIT, that is 2–1 superlattice structure of BTN–BIT. The BTN–BIT film with 2–1 superlattice structure has large remanent polarization (2Pr = 50 μC/cm2) and large coercive field (2Ec= 350 kV/cm). La-doped BTN–BIT thin film has also large remanent polarization (2Pr = 52 μC/cm2) and relatively small coercive field (2Ec= 220 kV/cm). The La-doped BTN–BIT film is fatigue-free on Pt electrodes up to 1010 switching cycles.