bluuebunny/crossref_metadata_2025 huggingface dataset:
From Ava to Mandalay: Toward Charting the Development of Burmese Yazawin Traditions
Authors: Kirichenko Alexey
Published: April 2011

Since the emergence of modern historiography of Burma (Myanmar), Burmese yazawin, or chronicles of kings, have been key scholarly sources. The most well-known of these chronicles are considered reliable after circa 1500 and provide a timeline of events for almost all research on precolonial Myanmar history. Despite this, we still have a quite vague understanding of textual genealogy and conditions in which these sources were produced, the foundations upon which they were constructed and the messages they carried. This article analyzes the corpus of Burmese yazawins and those narrative sources linked to yazawins that were instrumental in their compilation. It addresses the issues of typology and genealogy of yazawins, as well as the reconstruction of their development in terms of scope, structure, and conceptual focus. It challenges some historiographic stereotypes with regard to yazawins as a whole and the nature of individual sources in particular, and identifies a number of distinct yazawin traditions. The role of elites of royal cities of Ava, Taungngu, and Pagan in the production of yazawins is explored. Development of yazawin traditions is analyzed both as a kind of established textual activity with its own dynamics and as a function of changes in the organization of power and textual culture. Finally, the author suggests a number of tasks to be addressed in future research. All in all, the paper is conceived as a contribution towards the textology and hermeneutics of Burmese narrative sources and history of ideas in Myanmar in general.
Control Strategies for an Inline Cooling Device in Hot Strip Processing of Innovative Steel Materials
Authors: Rieger Thomas , Bülters Oliver , Bian Ing. Jian
Published: April 2011

Heat treatment of steel is used to adjust different microstructures and mechanical properties. The Quenching and Partitioning (Q&P) process or cyclic annealing for grain refinement lead to increased strength and ductility. Both approaches demand a strict temperature control and a close strip temperature tracking. A control strategy for optimal properties is developed. Herefore a one-stand laboratory scale hot rolling process line was equipped with a water cooling section. A detailed temperature control during the cooling process was established accounting for strip thickness and velocity, set point temperatures, and amount of water cooling. While industrial set points and parameters of closed-loop controllers are often empirical, the presented control system and strategies are investigated by MatLab-Simulink. The improved material properties were evaluated in annealing tests. The control system for the cooling track reduces the temperature gradient within the strip to 12 K. The simulation of the cooling track gives an optimal set point. As a prerequisite for a controlled design of time-temperature-cycles, it can be calculated for various process parameters. Grain sizes <5 μm are achieved by cyclic annealing and accompanied by increased strength and ductility. The Q&P treatment produces tempered martensite and retained austenite with improved mechanical properties.
Evaluation of a Handwipe Disclosing Method for Lead
Authors: Ashley Kevin , Wise Tamara J. , Esswein Eric J.
Published: April 2011

A qualitative chemical screening method for lead in wipe samples was evaluated for its utility in detecting the presence of lead in collected dust; preliminary evaluation of the performance of the method is reported here. In evaluating the method on pure lead compounds, the observed intensity of the characteristic color change due to the presence of lead was generally consistent with the relative solubilities of the tested compounds. Some pure (non-lead) metal compounds (e.g., those of Ag, Ba, Bi, Ca, Cd, Hg, and Sr) were found to give false positive results. Several representative lead-containing reference materials were also tested, and the qualitative test results differed for different materials. For materials collected on wipes, the method was found to be effective for detecting lead in several sample matrices commonly found in occupational settings. The technique was also applied on-site on dermal samples collected at field locations.
Influencing Factors of Heat Transfer Coefficient in Air and Gas Quenching
Authors: Xiao Bowang , Wang Gang , Sisson Richard D. , Rong Yiming
Published: April 2011

Cooling rates of work pieces in heat treating processes heavily depend on the interfacial heat transfer coefficient (HTC) between work pieces and quenchants. Because the HTC plays an important role in the resulted distortion, residual stress, and mechanical property distributions, understanding how the HTC varies with respect to various influencing factors is of importance for an optimal quenching process. In this paper, the influencing factors such as air/gas velocity, pressure, temperature, gas mixture and part orientation, air/gas temperature, air humidity, surface roughness, oxide, and material to the variation of HTC are studied experimentally by using the Center for Heat Treating Excellence quenching system and theoretically by using empirical equations.
Simulation of Austenitization Processes in Fe–C Steels by Coupled Cellular Automaton and Finite Difference Methods
Authors: Roósz András , Karacs Gábor
Published: April 2011

The aim of the simulation was to calculate the austenitization processes in plain carbon steels with different carbon concentrations. As the first step of simulation, an initial structure was generated where the diameters of pearlite colonies, the thickness and orientation of cementite lamellae, and the thickness of pro-eutectoid ferrite or even secondary cementite were changed. By this method, similar structures to the real ones were obtained. To solve the nucleation problem, a free enthalpy model was used, which makes difference between the places of nuclei. The diffusion equation (Fick II.) in case of the grain growth of austenite was solved by the Finite Differential Method. Nuclei can be formed at the boundary of pearlite colonies, at the boundary of the pro-eutectoid ferrite and cementite, or rarely at the boundary of cementite and ferrite lamellae too. The grain growth model calculates the carbon diffusion through both ferrite and austenite phases. The simulation runs as a coupled Cellular Automaton and Finite Difference Methods.
Isothermal Martensite Formation at Sub-Zero Temperatures
Authors: Stojko Allan , Hansen Mikkel F. , Slycke Jan , Somers Marcel A. J.
Published: April 2011

Sub-zero treatment of steels with an Mf below 0°C relies (partly) on a continuation of the martensite formation. The present work reports on the observation of isothermal martensite formation in the sub-zero temperature regime for two steels: AISI 1070 and AISI 52100. Samples were austenitized, quenched in oil, and thereafter investigated with vibrating sample magnetometry, which allows a quantitative assessment of the fraction of retained austenite as a function of the sub-zero temperature and time. Isothermal martensite formation was observed on interrupting the continuous cooling (5 K/min) at temperatures in the range of 80–233 K. The kinetics of isothermal martensite formation depends strongly on the temperature and can be described by Johnson–Mehl–Avrami–Kolmogorov kinetics. Isothermal experiments with dilatometry indicated the occurrence of a volume increase on isothermal holding, consistent with a continuation of the martensitic transformation. On prolonged isothermal holding, a volume reduction was observed for AISI 52100, but not for AISI 1070.
Dye-Sensitized Solar Cells Based on a Natural Low Cost
Halochromic Sensitizer
Authors: Ibrahim Michael I. , Bassil Maria J. , Demirci Umit B. , El Haj Moussa Georges , El Tahchi Mario R. , Miele Philippe
Published: April 2011

Since their re-introduction as new generation solar cells in 1991,
dye-sensitized solar cells (DSSCs) have been studied extensively to improve
their efficiency and their stability. Few papers have reported the usage of
natural dyes in the fabrication of DSSCs. We are most interested in these
dyes being easy to extract, low cost and with tunable absorption. For
example, Anthocyanin is extracted from red cabbage and is present in a
multitude of colors ranging from red to yellow to violet according to the
pH. In this study, two industrial types of titanium dioxide powders, the
Degussa P 25 and the Crystal 128 with different particle sizes 21 and 200 nm
respectively, were used to prepare DSSCs. The dye used is anthocyanin and
its color is varied by varying the pH of the medium. The pH effect on the
light absorption of anthocyanin in the visible range and the optical
properties of titanium dioxide dyed with anthocyanin and coumarin 102 are
investigated using UV-Vis spectroscopy. The open-circuit voltage of all the
samples is tested and it if found out that it is dependant on the dye
color.
The First Molecular Wheel: A Theoretical
Investigation
Authors: Brunetto Gustavo , Sato Fernando , Bouju Xavier , Galvao Douglas S.
Published: April 2011

Recently, the first molecular nanowheel was synthesized and characterized
from Scanning Tunneling Microscope (STM) experiments. It was demonstrated
that a specifically designed hydrocarbon molecule
(C44H24) could roll on a copper substrate along the
[110] surface direction. In this work we report a preliminary theoretical
analysis of the isolated molecule and of its rolling processes on different
Cu surfaces. We have used ab initio and classical molecular
dynamics methods. The simulations showed that the rolling mechanism is only
possible for the [110] surface. In this case, the spatial separation among
rows of copper atoms is enough to ‘trap’ the molecule and to create the
necessary torque to roll it. Other surface orientations ([111] and [100])
are too smooth and cannot provide the necessary torque for the rolling
process.
Characterization of InGaN/GaN Multiple Quantum Wells Grown on Sapphire Substrates by Nano-scale Epitaxial Lateral Overgrowth Technique
Authors: Fong W.K. , Leung K.K. , Surya Charles
Published: April 2011

High-quality InGaN/GaN multiple quantum wells (MQWs) were fabricated on nano-scale epitaxial lateral overgrown (NELO) GaN layers which was prepared using nanometer-scale SiO2 islands, with an average diameter and interdistance of 300nm and 200nm respectively, as the growth mask. The active region of the device consists of five periods of GaN/InGaN MQWs were grown on top of the NELO layer using MOCVD technique. It is observed that some of the dislocations from the undoped GaN were blocked by the SiO2 growth mask and typical threading dislocation (TD) density found in the NELO samples is ~7.5×107cm-2. Significant improvement in the electroluminescence (EL) is observed which is believed to partly arise from the improvement in the internal quantum efficiency (ηi). The experimental data on the temperature dependence of the photoluminescence (PL) were fitted to a proposed model using Levenberg-Marquardt approximation. Based on our analyses it is found that the relative improvement in ηi at 300K over a control device grown in the same growth condition but without the NELO layer to a NELO device is only 0.59. It is generally accepted that TD is the non-radiative recombination center which affects the IQE. Therefore, room-temperature IQE values also support that NELO device exhibits lower TD density.
Solution Processable n-Type Perylene Diimide Copolymers for
Organic Photovoltaics
Authors: Liang Ziqi , Cormier Russell A. , Nardes Alexandre M. , Gregg Brian A.
Published: April 2011

Perylene diimides are known as promising n-type semiconductor building
blocks. Here we report the synthesis and characterization of a set of three
soluble poly(perylene diimide)s and their preliminary characterization in
organic photovoltaic cells. These polymers are made through the
polycondensation of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)
with a variety of poly(ethylene glycol) (PEG)- or poly(propylene glycol)
(PPG)-based diamine comonomers. The flexible spacer offers increased
solubility in organic solvents and allows the perylene core to assume a
conformation that promotes favorable cofacial π–π interactions. Mixtures of
these polymers with the hole-transporting polymer, poly(3-hexylthiophene)
(P3HT) result in significant fluorescence quenching. However, the phase
separation occurs on a scale too large for a bulk heterojunction solar cell.
The PPGylated poly(perylene diimide) shows an unusually low free electron
concentration (~1.0 × 1012 cm-3) and therefore makes
an excellent model system for future doping studies. These new polymers may
have promise as stable electron-conductive layers with large
light-absorptivities in solution-processable applications of organic
electronics.
Novel Imprinting Techniques for Fabrication of Multilevel Flexible Electronics
Authors: Turkenburg Daniël , Rendering Henk , Hovestad Arjan , Stroeks Niki , Maury Pascale , Moonen Pieter , Huskens Jurriaan , Barbu Ionuţ , Meinders Erwin
Published: April 2011

We report a novel method to selectively deposit materials from solution into imprinted micro-capillaries. Dewetting of the solvent just outside the capillaries is balanced to evaporation inside the capillaries. In this way conductive μ-wires can be self-assembled and self-aligned on flexible substrates opening the route to faster and cheaper plastic electronics.
Dielectric Properties of BST/(Y2O3)x(ZrO2)1-x/BST Trilayer Films
Authors: Sahoo Santosh K. , Misra D.
Published: April 2011

Thin films of Ba1-xSrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and high dielectric breakdown strength. Various approaches have been used to improve the dielectric properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant as well as dielectric loss. In this work the effect of Y2O3 doped ZrO2 on the dielectric properties of BST/ZrO2/BST trilayer structure is studied. The structure Ba0.8Sr0.2TiO3/(Y2O3)x(ZrO2)1-x/Ba0.8Sr0.2TiO3 is deposited by a sol-gel process on platinized Si substrate. The composition (x) of the middle layer is varied while keeping the total thickness of the trilayer film constant. The dielectric constant of the multilayer film decreases with the increase of Y2O3 amount in the film whereas there is a slight variation in dielectric loss. In Y2O3 doped multilayer thin films, the dielectric loss is lower in comparison to other films and also there is good frequency stability in the loss in the measured frequency range and hence very suitable for microwave device applications.
Fundamental Properties and Nano-imprintabilities of Zr-, Pd- and Cu-based Glassy Alloy Thin Films
Authors: Takenaka Kana , Saidoh Noriko , Nishiyama Nobuyuki , Inoue Akihisa
Published: April 2011

With the aim of investigating fundamental properties and nano-imprintabilities of glassy alloy in the film form, Zr49Al11Ni8Cu32, Pd39Cu29Ni13P19 and Cu38Zr47Al9Ag6 alloy thin films were fabricated on Si substrate by a magnetron sputtering method. These thin films exhibit distinct glass-tradition phenomenon and large supercooled liquid region of about 80 K, confirming as a glassy structure and have very smooth surface and sufficient hardness to maintain imprinted shape, which are suitable for nano-imprint processing. Moreover, thermal nano-imprintabilies of these obtained films are demonstrated by using a dot array mold with a dot diameter of 90 nm and a pitch of 180 nm. Surface observations revealed that periodic nano-hole arrays were successfully imprinted on the surface of these films and precisely corresponded to the periodic dot pattern of the mold. Particularly, Pd-based glassy alloy thin film indicated more precise pattern imprintability, namely, more flat residual surface plane and sharper hole edge. These results suggest that these glassy alloy thin films, especially Pd-based glassy alloy thin film have high potential for application to the nano-imprinting materials.
Deformation Behavior of a Quaternary Mo-Nb-Si-B Alloy
Authors: Alur A.P. , Sakidja R. , Wang P. , Jain P. , Perepezko J.H. , Kumar K.S.
Published: April 2011

The microstructure and compression response of a quaternary Mo-Nb-Si-B alloy has been examined in in the temperature interval 1200°C-1600°C and in the strain rate regime 10–4 s–1 to 10–6 s–1 and compared to earlier results on the ternary Mo-Si-B alloys The microstructure is composed of a three-phase microlamellar eutectic composed of the Mo-Nb solid solution phase, the T1 and the T2 intermetallic phases. Compression test confirm significantly superior creep resistance for the eutectic alloy compared to the ternary Mo-rich Mo-Si-B alloys with virtually no microstructural degradation.
A Novel Surface Topographical Concept for Bone
Implant
Authors: Munir G. , Di Silvio L. , Edirisinghe M.J. , Bonfield W. , Huang J.
Published: April 2011

Template-assisted electrohydrodynamic atomization (TAEA) spraying
deposition, a recently developed and an electric-driven jet-based technique
has been used to prepare bioactive surface topography on titanium (Ti).
Nanometer-scaled SiHA (nanoSiHA), which closely resembles the bone mineral,
has been synthesized and deposited on Ti surfaces with a range of patterns,
such as pillars and tracks. A human osteoblast (HOB) cell model has been
used to evaluate the in vitro cellular responses to nanoSiHA deposition.
alamarBlue™ assay showed that nanoSiHA patterns are able to encourage the
attachment and growth of HOB cells in comparison to those of nanoSiHA
coating. The preferential growth of HOB cells was found along and across the
track, HOB cells were also found to stretch between two tracks. Image
analysis of HOB cell responses to the size of nanoSiHA pattern showed that
the length of HOB cells was proportional to the gaps between the tracks
until reaching the maximum length of 110 μm. The results indicate that the
distance between the structures is paramount over the width. Our study will
pave the way to control and guide cellular responses for new generation of
bone implants.
A factorial design of experiments approach to synthesize CZTS absorber material from aqueous media
Authors: Sarswat Prashant K. , Free Michael L. , Tiwari Ashutosh
Published: April 2011

Cu2ZnSnS4 (CZTS), an emerging p-type quaternary chalcogenide, offers many potential advantages as an absorber material. Using factorial design of experiments approach, single stage Cu-Zn-Sn co-electrodeposition from aqueous solution followed by annealing is reported in this paper. Factorial experiments facilitate to study the effects of each factor on the response variable as well as effects of interactions between individual factors on the response variable. Selected factors include concentration of individual ionic species, time of sulfurization and amount of complexing agent, whereas CZTS phase, band gap, carrier concentration, open circuit voltage, and morphological characteristics are the response variables. A model has been developed to show and predict the domain for the best possible factors for CZTS based device fabrication.
Work Function Controlled Printed Metal Alloy Pattern Prepared by Using Pressure Annealing Technique
Authors: Yoshida Manabu , Suemori Kouji , Uemura Sei , Hoshino Satoshi , Takada Noriyuki , Kodzasa Takehito , Kamata Toshihide
Published: April 2011

We have developed the pressure annealing technique for fabricating low work function metal pattern on plastic substrate. In general, the difficulty to print conductive low work function metal patterns is caused by the insulating metal oxide layer covering on metal particles included in metal paste. The pressure annealing technique can destruct the metal oxide layer and can form conductive layer on printed metal pattern. Further, we have confirmed that a binary solid solution is easily formed on metal patterns including two kinds of metal particles by using the pressure annealing technique. Changing the composition ratio of the binary metal paste led to the work function control of the pressure-annealed metal patterns. Formation of the binary solid solution was confirmed by using XRD spectra, and work function values were measured by using photoelectron emission spectra. In the case of the binary metal paste of Cu and Zn, we have succeeded in controlling work function from 3.8 eV to 5.0 eV. Since the Cu-Zn paste is composed of relatively low price metals, this would be applicable to large-scale flexible electronic devices.
Thin Films of AuCuAl Shape Memory Alloy for Use in Plasmonic Nano-actuators
Authors: Bhatia Vijay , Thorogood Gordon , Dowd Annette , Cortie Michael B.
Published: April 2011

We describe the fabrication and structure of nanoscale thin films of β phase shape memory alloys with the nominal atomic stoichiometry Au7Cu5Al4 (corresponding to 5.8 wt% Al). These alloys possess properties that suggest they could be used in nanoscale actuators. The films described here are between 20 and 50 nm thick which is below the thickness at which some other shape memory alloys cease to transform. However, microstructural and X-ray studies confirm that the coatings still exhibit the displacive transformations that are a prerequisite for the shape memory effect.
Structural, Optical and Magnetic properties of Co-doped ZnO Nanopowders
Authors: Jáuregui-Rosas Segundo R. , Perales-Perez Oscar J. , Noriega Lourdes A. , Castillo Luis A.
Published: April 2011

Nanocrystalline Zn1-xCoxO powders exhibiting a preferential crystal growth along the (002) plane have been synthesized in the atomic fraction, ‘x’, range of 0.0-0.0625 by a wet chemical method. The effect of the dopant concentration on the corresponding structural, optical and magnetic properties was also evaluated. XRD analyses evidenced the development of single-phase wurtzite with no traces of any impurity for all the dopant levels. The higher intensity of the (002) peak, when compared to the XRD peaks in bulk ZnO, indicates the preferential crystal growth along the c-axis in hexagonal wurtzite cell. The linear dependence of cell parameters a and c with ‘x’ suggests the actual replacement of Zn by Co ions in the host oxide lattice. Micro Raman spectroscopy measurements showed a band centered at 535cm-1, which can be assigned to a local vibrational mode related to Co species in addition to the normal modes associated with wurtzite. The relative broadening of this band at 535cm-1 was enhanced by increasing ‘x’. The other characteristic bands of ZnO corresponding to A1 (E2, E1) and E2High modes were red shifted for all Co contents. UV-vis measurements showed that the energy band gap of as-synthesized nanopowders decreased with increasing Co2+ content up to x = 0.03 and increased for higher contents. Room-temperature magnetization measurements revealed the paramagnetic behavior of the Co-doped ZnO nanopowders.
Early Nucleation Events in the Biomineralization of Calcium
Phosphates
Authors: Xie Baoquan , Nancollas George
Published: April 2011

Our work focuses on the earliest events of homo-/heterogeneous nucleation
from an initial supersaturated solution to the subsequent growth of nuclei.
The combined use of conductance, together with hydrogen and calcium ISEs has
provided new insights into the mechanisms of crystal nucleation and phase
stability. We propose that two types of ACP are formed during HAP
nucleation. The initial subcritical calcium-phosphate ion clusters form an
amorphous [CaHPO4·xH2O] phase (ACP-1), which
transforms to amorphous [Ca3(PO4)2]
(ACP-2), and subsequently to HAP. This study is a major step forward in our
understanding of the earliest nucleation events in vitro and in vivo.
Additives may influence HAP nucleation by interacting with ACP clusters
during the early induction period.
Characterization of Type B Carbonate Apatite Sintered Bodies
Authors: Watanobe N. , Yoshioka T. , Ikoma T. , Kuwayama T. , Higaki T. , Cross J.S. , Tanaka J.
Published: April 2011

The dissolution kinetics of type B carbonate apatite (CAp) disks sintered at different temperatures were investigated under acidic conditions similar to an osteoclastic desorption process in bone remodeling. The type B CAp disks, which were uniaxially pressed at 98MPa and sintered at temperatures of 600 to 700 ºC, showed single crystalline phase and a high relative density of 60-62 % compared to the stoichiometric density of 3.16g/cm3of hydroxyapatite (HAp). The dissolution rate of type B CAp disks sintered at 650 ºC was 3.5 times faster than that of HAp disks at 650 ºC. These results indicate that the Type B CAp sintered disks show potential use as a biodegradable material for artificial bone.
Molecular Dynamics of Cation Hydration in the Presence of
Carboxylated Molecules: Implications for Calcification
Authors: Hamm Laura M. , Wallace Adam F. , Dove Patricia M.
Published: April 2011

Biomolecules rich in aspartic acid (Asp) are known to play a role in
biomineral morphology and polymorph selection, and have been shown to
greatly enhance the growth kinetics of calcite. The mechanism by which these
compounds favor calcification may be related to their effects upon cation
solvation. Using molecular dynamics, we investigated the influence of small
carboxylated molecules on the hydration states and water exchange rates of
divalent cations. We show that the carboxylate moieties of Asp promote
dehydration of Ca2+ and Sr2+ and that contact ion pair
(CIP) formation is not required to disrupt the hydration of these cations.
Ca2+- Asp and Sr2+ - Asp CIP formation decreases
the total inner sphere coordination from an average of 8.0 and 8.4 in bulk
water to 7.5 and 8.0, respectively. Water residence times estimated for
Mg2+, Ca2+and Sr2+ follow the expected
trend of decreasing residence time with increasing ionic radius. In the
presence of Asp, both solvent-separated ion pair (SSIP) and CIP formation
decrease the residence times of Ca2+and Sr2+ inner
sphere water molecules. Comparable impacts on Mg2+ hydration are
not observed. Mg2+ - Asp CIP formation is energetically
unfavorable and Asp does not affect Mg2+ inner sphere water
residence times.
Preparation and Characterization of the Single-Layered Cobaltate La2-xCaxCoO4
Authors: Fuchs D. , Merz M. , Schneider R. , Löhneysen H. v.
Published: April 2011

Polycrystalline samples of the single-layered cobaltate La2-xCaxCoO4 were prepared in a wide doping range of 0 ≤ x ≤ 1.5. Structural properties were characterized at room temperature. The orthorhombic distorted structure of the mother compound La2CoO4 changes to a tetragonal structure for x = 0.5 and then becomes orthorhombic again for x > 0.5. The magnetic properties were investigated in the temperature range from 5 K ≤ T ≤ 300 K. With increasing hole-doping a successive decrease of antiferromagnetic exchange is observed for x ≤ 0.5 whereas an increase of ferromagnetic exchange evolves for x ≥ 0.5.
Ohmic and Highly Reflective Ag based contacts on p-GaN for Resonant Cavity Light Emitting Diodes
Authors: Kumbham V. , Kuchibhatla S. , Lee K. , Rodak L.E. , Narang V. , Korakakis D. , Hornak L.A.
Published: April 2011

Low resistance and high reflectance ohmic contacts on p-type GaN were achieved using an Ag-based metallization scheme. The ohmic nature of the contacts can be obtained by annealing the contacts in an O2 ambient. However, Ag based contacts degrade due to agglomeration of Ag when annealed above 400 oC [1]. In this work a Ni (1 nm)/Ag (150 nm)/Pt (50 nm)/Ni (20 nm)/Au (50 nm) metallization stack is investigated to reduce Ag agglomeration. The inclusion of platinum as a diffusion barrier is expected to suppress excess oxygen diffusion into the Ag films thereby preventing Ag agglomeration and can also provide high thermal stability when compared to other metallization schemes. The reflectivity of this kind of metallization scheme is around 85-90 % in the wavelength range of 400-600 nm making it suitable for blue and green LEDs, with a specific contact resistivity value comparable to other well developed contacts to p-GaN.
Effects of argon to oxygen ratio and post annealing on R.F. sputtered SnO2 thin film for ethylene gas detection
Authors: Ahn Hosang , Kim Seon-Bae , Kim Dong-Joo
Published: April 2011

Optimum processing conditions for fabricating SnO2 thin films were investigated to detect low ppm levels of ethylene gas for future on-field gas sensor applications. Different argon-to-oxygen ratios during R.F. sputtering were attempted to find the optimum gas ratio in depositing SnO2 thin film. Post-annealing was performed at 650°C to investigate the influence of film property change on ethylene sensing property of sensor. As-deposited and post-annealed films prepared under four different argon-to-oxygen ratios were studied by SEM, XRD, and sensitivity measurement. It was found that the stoichiometry and crystallinity of SnO2 films determined by post annealing was more influential than those by the argon to oxygen ratio during R.F sputtering on ethylene gas detection. An ethylene gas-sensing mechanism on R.F. sputtered SnO2 thin films for the design of processing conditions is proposed.
Simulating Thermal Cycling and Isothermal Deformation Response of Polycrystalline NiTi
Authors: Manchiraju Sivom , Gaydosh Darrell J. , Noebe Ronald D. , Anderson Peter M.
Published: April 2011

A microstructure-based FEM model that couples crystal plasticity, crystallographic descriptions of the B2-B19′ martensitic phase transformation, and anisotropic elasticity is used to simulate thermal cycling and isothermal deformation in polycrystalline NiTi (49.9at% Ni). The model inputs include anisotropic elastic properties, polycrystalline texture, DSC data, and a subset of isothermal deformation and load-biased thermal cycling data. A key experimental trend is captured—namely, the transformation strain during thermal cycling is predicted to reach a peak with increasing bias stress, due to the onset of plasticity at larger bias stress. Plasticity induces internal stress that affects both thermal cycling and isothermal deformation responses. Affected thermal cycling features include hysteretic width, two-way shape memory effect, and evolution of texture with increasing bias stress. Affected isothermal deformation features include increased hardening during loading and retained martensite after unloading. These trends are not captured by microstructural models that lack plasticity, nor are they all captured in a robust manner by phenomenological approaches. Despite this advance in microstructural modeling, quantitative differences exist, such as underprediction of open loop strain during thermal cycling.
Transition from Microscale-Faceted Structures to Ultra-Dense GaN Nanowires
Authors: Teker Kasif , Oxenham Joseph A.
Published: April 2011

Creation of nanoscale building blocks with various sizes and shapes are critical for the progress of nanotechnology. The synthesis of GaN nanowires by chemical vapor deposition (CVD) using Ga and NH3 as source materials on SiO2/Si substrate was systematically studied. Various types of catalyst materials, including gold (film and nanoparticle), nickel (film and nanoparticle), silver, cobalt and iron, have been used. The growth runs have been carried out at temperatures between 800 and 1100oC under two different carrier gases; H2 and Ar. Initial growth runs using Ar as carrier gas resulted in microscale-faceted nanostructures and short nanorods regardless of the growth temperature or reactor pressure. We have successfully achieved ultra-dense interwoven long nanowires using hydrogen as carrier gas at 1100oC. In fact, the yield has been very high for both gold and nickel catalysts. It should be emphasized that combination of high-temperature and hydrogen has resulted in ultra-dense interwoven long GaN nanowires. These results suggest a radical change in growth kinetics at high temperatures in the presence of H2. The GaN nanowire diameters are in the range of 15 nm to 50 nm and lengths up to hundred microns. The grown nanowires have been characterized by scanning electron microscopy (SEM with EDS), atomic force microscopy (AFM), x-ray diffraction (XRD), and transmission electron microscopy (TEM).
Application of liquid desiccant for enhanced lifetime of active
matrix organic light emitting diodes
Authors: Lee Byoung Duk , Cho Yoon-Hyung , Oh Minho , Kim Yong Tak , Cho Sang-Hwan , Lee So Young , Chung Yoon Ah , Song Seung Yong , Lee Jong Hyuk , Kim Sung Chul
Published: April 2011

To enhance the lifetime of large-sized active matrix organic light emitting
diodes (AMOLEDs), we developed a liquid desiccant for encapsulation. The
liquid desiccant was prepared by mixing nano-sized calcium oxide (CaO)
powders and silicone binder including polyalkylalkenylsiloxane,
polyalkylhydrogensiloxane and platinum compound. It was confirmed that
liquid desiccant had an effect on absorption of penetrated moisture and
oxygen through calcium tests. Also, the test cells encapsulated with only
epoxy sealant dispensed at the edge of the cell developed dark spots within
100 hrs, which grew larger with time at 85 oC and 85 % R.H. On the other hand, the test cell sealed with epoxy
sealant and liquid desiccant showed no dark spots and retained 97% of its
initial luminance even after being stored for 800 hrs at 85 oC and 85 % R.H. Furthermore, the accelerating storage lifetimes of
31-inch bottom-emitting AMOLEDs with epoxy sealant and liquid desiccant
showed about 1000 hrs. These results suggest that the liquid desiccant can
be applied to encapsulation of large-sized AMOLEDs.
Ultrafast Charge Separation at a Single-walled Carbon Nanotube –
Polymer Interface
Authors: Stranks Samuel D. , Weisspfennig Christian , Parkinson Patrick , Johnston Michael B. , Herz Laura M. , Nicholas Robin J.
Published: April 2011

We report the observation of an ultrafast (~ 430 fs) charge transfer process
at the interface between a single-walled carbon nanotube (SWNT) wrapped by a
semi-conducting polymer, poly(3-hexylthiophene) (P3HT), creating free
polarons on both materials. The addition of excess P3HT as a surrounding
network allows these free polarons to be long-lived at room temperature. Our
results suggest that SWNT-P3HT blends incorporating only 1% fractions of
SWNTs can achieve a charge separation efficiency comparable to a
conventional 60:40 P3HT-fullerene blend, provided small-diameter tubes are
embedded in an excess P3HT matrix.
Correlation among the ionization potential, built-in potential,
and the open-circuit voltage of multi-layered organic photovoltaic
devices
Authors: Itoh Eiji , Shirotori Toshiki
Published: April 2011

We have investigated the current-voltage characteristics of the
multi-layered photovoltaic devices consisting of ITO/oxide /p-type
(donor)/fullerene/ bathocuproine (BCP)/ Al structures. We chose various
p-type (donors) small molecules and polymers in order to tune the values of
ionization potential (IP) of donor molecules. The open-circuit voltage (Voc)
increases with the increment of IP of donor materials. However,
VOC was limited at ~0.6-0.7V for the devices without oxide
layer. On the other hand, the VOC increases up to 0.9V for the
devices with NiO and to ~ 1.1V for the devices with MoOX as a
hole extraction buffer layer, respectively. We also estimated the
work-function differences between Al and the oxide as 0.7, 0.9-1.0, and
1.2-1.3 eV for the device without oxide, with NiO, and with MoOX,
respectively. We therefore concluded the value of VOC is limited
by the lower part of VOC and energy difference between the LUMO
of fullerene and the HOMO of donor ΔE.
Probing the Orbital Levels of Engineered Fullerenic Molecules
from a Nonvolatile Memory Cell
Authors: Xu Sarah Q. , Shaw Jonathan , Kan Edwin C.
Published: April 2011

The Coulomb blockade behavior was observed for both C60-PCBM and
C70-PCBM at room temperature utilizing a nonvolatile memory
cell fabricated through a liquid-transfer process. Room-temperature and
low-temperature (10K) electrical characterizations verified the blockade
effect was originated from both molecular energy levels and single electron
charging energy. Molecular orbital energy was extracted and shown good
agreement with the literature [1].The successful integration and operation
of this hybrid structure signified a strong potential for molecule-based
electronic device design.
Effects of air and light exposure on the opto-electronic
properties of polymer:fullerene solar cells
Authors: Sio Antonietta De , Como Enrico Da , Hauff Elizabeth von , Parisi Jürgen
Published: April 2011

In this study we investigate how exposure to ambient air and light during
device processing affects the opto-electronic properties of
poly-3-hexylthiophene (P3HT) :
[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk
heterojunction solar cells (BHJ). The properties of pure P3HT layers
prepared in an inert atmosphere, under ambient conditions, and additionally
degraded under light in ambient conditions were investigated using
photoluminescence (PL) and photoinduced absorption (PIA). It was observed
that exposure to air during processing leads to oxygen doping of the
polymer. Exposure to air combined with light was found to significantly
decrease the PL and PIA signals. The current-voltage (I-V) and external
quantum efficiency (EQE) characteristics of solar cells fabricated in an
inert atmosphere were compared to solar cells processed under ambient
conditions. It was observed that processing in air leads to a reduction in
the photocurrent in the devices which is attributed to electron trapping by
oxygen in the active layer.
The Study of Improving the Conversion Efficiency and Reducing the Thickness of the HIT Solar Cell
Authors: Hirayama Yasuko , Inoue Hirotada , Matsuyama Kenta , Tsunomura Yasu umi , Fujishima Daisuke , Yano Ayumu , Taira Shigeharu , Nishiwaki Takeshi , Asaumi Toshio , Kinoshita Toshihiro , Taguchi Mikio , Sakata Hitoshi , Maruyama Eiji
Published: April 2011

In order to reduce the power-generating cost of silicon solar cells, it is necessary to achieve a high conversion efficiency using a thinner crystalline silicon (c-Si) substrate. The HIT solar cell is an amorphous silicon (a-Si) /crystalline silicon (c-Si) heterojunction solar cell that makes it possible to realize excellent surface passivation and hence high open circuit voltage (Voc). In addition, its symmetrical structure and a low-temperature fabrication process that is under 200°C provide advantages in reducing thermal and mechanical stresses within the device so that it can easily be applied to thinner solar cells. We fabricated HIT solar cells using thin wafers from 58-98 μm, and achieved a 22.8% conversion efficiency with a HIT solar cell using a 98-μm-thick wafer, and an excellent Voc value of 0.747 V with a HIT solar cell using a 58-μm-thick wafer.
Dispersed Nanoelectrodes for High Performance Gas Sensors
Authors: Tricoli Antonio , Pratsinis S.E.
Published: April 2011

Integration of nanoparticles in electronic devices such as sensors, actuators, batteries, solar and fuel cells is a key technological development for advancing their performance and miniaturization. Frequently, however, the benefit of nanoscale is lost by poor electrical conductivity through such nanoparticle structures. As a result, it is challenging to achieve both attractive conductivity and maximal performance by the device. Recently it was demonstrated that flame-made nanoparticles can be directly deposited onto substrates to form porous thick films of controlled thickness for application as gas sensors. The mechanical stability of FSP-deposited layers can be greatly increased by in situ annealing showing compatibility even with fragile CMOS-based substrates. Here, a novel asymmetric electrode assembly is described that greatly reduces the resistance of a nanostructured layer and maximizes its performance: Nanoparticles with tailored conductivity (e.g. Ag, CuO, Au) serving as electrodes are stochastically deposited by a scalable technique either below or above a functional (e.g. SnO2, TiO2, WO3) film decreasing the effective length of the resistive components. As the distance between electrodes is at the nanoscale, the total film resistance is drastically decreased. The feasibility of this assembly is demonstrated with solid state sensors having controlled resistance and exceptionally high sensitivity.
Growth of CaFeOX/LaFeO3 Superlattice on SrTiO3(100) Substrates
Authors: Iwata Nobuyuki , Huijben Mark , Rijnders Guus , Yamamoto Hiroshi , Blank Dave H. A.
Published: April 2011

The CaFeOX(CFO) and LaFeO3(LFO) thin films as well as superlattices were fabricated on SrTiO3(100) substrates by pulsed laser deposition (PLD) method. The tetragonal LFO film grew with layer-by-layer growth mode until approximately 40 layers. In the case of CFO, initial three layers showed layer-by-layer growth, and afterward the growth mode was transferred to two layers-by-two layers (TLTL) growth mode. The RHEED oscillation was observed until the end of the growth, approximately 50nm. Orthorhombic twin CaFeO2.5 (CFO2.5) structure was obtained. However, it is expected that the initial three CFO layers are CaFeO3 (CFO3) with the valence of Fe4+. The CFO and LFO superlattice showed a step-terraces surface, and the superlattice satellite peaks in a 2θ-θ and reciprocal space mapping (RSM) x-ray diffraction (XRD) measurements, indicating that the clear interfaces were fabricated.
Processing iron aluminides by heavy deformation for improved room temperature strength-ductility and for high temperature creep strength
Authors: Morris David G. , Muñoz-Morris Maria Antonia
Published: April 2011

Iron aluminides show many interesting properties, but still show relatively poor ductility at room temperature and only moderate creep resistance at temperatures above about 600ºC. Processes of severe plastic deformation have been investigated for a wide range of ductile alloys over the past decade, but have hardly been considered for intermetallics. This presentation discusses two studies aimed at refining microstructure by the use of severe plastic deformation of iron aluminides. The first considers processing Fe3Al by heavy cold rolling, followed by annealing for recovery or recrystallization, with an objective of refining grain size to improve strength at the same time as ductility. The high strength and poor ductility of the work hardened material leads to a danger of cracking during rolling, which is a problem for manufacturing large quantities of healthy material. Suitable rolling and recovery treatments can, nevertheless, lead to strong materials with some plastic ductility. A different technique of multidirectional, high-strain and high-temperature forging applied to a boride-containing Fe3Al alloy produces a material with large grain size and refined dispersion of boride particles. These particles lead to a considerable increase in creep strength under conditions of moderate stresses at temperatures around 700ºC. This high-strain forging technique can be seen as an intermediate processing method between conventional wrought metallurgy and mechanical-alloying powder metallurgy. This technique offers the possibility to improve high temperature behaviour of such intermetallics containing second-phase dispersions, and can be scaled to produce large quantities of high-quality material.
Radiation-Enhanced Aqueous Dissolution of Minerals
Authors: Dukes Catherine A. , Baragiola Raúl A.
Published: April 2011

Mineral samples of varying petrology, exposed to ion irradiation and subsequently immersed in water or exposed to a humid environment, show up to 60% depletion of specific surface atoms (Mg, Ca, K, and Na) — a depletion that is enhanced 26,000x compared to unirradiated surfaces. Surface depletions of irradiated minerals exposed to water were measured using X-ray photoelectron spectroscopy. Irradiations were performed with 4 keV Ar+ ions at fluences from 1014 – 1019 ion cm-2; samples were subsequently exposed to liquid water or humid air (35º C and 70% RH). Analyses were done before irradiation, after irradiation, and after exposure to water, allowing identification of changes in composition due solely to ion irradiation or combined with water exposure. Before water exposure, we observe no significant change in stoichiometry of the minerals for ion fluences <1018 ions cm-2. We find incongruent depletion of 60% Mg for forsterite after exposure to humidity or three minutes (or more) water immersion. Augite undergoes reduction in the surface concentration of approximately 30% Mg, 40% Ca, and 55% Na after 1.9 x 1017 Ar cm-2 and immersion in HPLC water (pH: 6.8) for three minutes. Depth profiles of the irradiated, water exposed, minerals show that the depth of the depleted region is on the order of the ion range, ~15nm. In addition, preliminary results for albite, anorthoclase, and microcline in water show significant depletions of Na, Na and K, and K, respectively, from the mineral surface.
Fatigue resistance of Fe3Al-based alloys
Authors: Gang Florian , Krüger Manja , Laskowsky Alexandra , Rühe Heike , Schneibel Joachim H. , Heilmaier Martin
Published: April 2011

The low cycle fatigue (LCF) behaviour of two cast as well as two hot extruded Fe3Al-based iron aluminide alloys, either with or without Cr, is investigated. All four alloys contain microalloying additions of Zr, Nb, C and B. Fatigue tests were carried out under strain control for strain amplitudes in the range of εa = 0.1 – 0.4 % for the cast alloys and εa = 0.1 – 0.7 % for the extruded materials, at frequencies of 1 Hz (extruded Fe3Al) and 3 Hz (all other alloys) and at room temperature and 300 °C. Within the first cycles all alloys show strong cyclic hardening. Furthermore the fatigue strain – fatigue life curves are steeper at 300 °C than at room temperature, showing increased fatigue strength at low cycle numbers due to increasing ductility and decreased fatigue strength at increasing cycle numbers because of reduced yield strength. Cr is found to have only a negligible influence on the fatigue behaviour of Fe3Al-based alloys. Comparison between the differently processed materials shows superior LCF properties of the hot extruded iron aluminides due to significantly smaller grain sizes.
Physical Metallurgy and Properties of β-solidifying TiAl Based Alloys
Authors: Clemens Helmut , Schmoelzer Thomas , Schloffer Martin , Schwaighofer Emanuel , Mayer Svea , Dehm Gerhard
Published: April 2011

In this paper, the physical metallurgy and properties of a novel family of high-strength γ-TiAl-based alloys is reviewed succinctly. These so-called TNM™ alloys contain Nb and Mo additions in the range of 3 - 7 atomic percent as well as small additions of B and C. For the definition of the alloy composition thermodynamic calculations using the CALPHAD method were conducted. The predicted phase transformation and ordering temperatures were verified by differential scanning calorimetry and in situ high-energy X-ray diffraction. TNM alloys solidify via the β-phase and exhibit an adjustable β-phase volume fraction at temperatures, where hot-working processes are performed. Due to the high volume fraction of β-phase these alloys can be processed isothermally as well as under near conventional conditions. In order to study the occurring deformation and recrystallization processes during hot-working, in situ diffraction experiments were conducted during compression tests at elevated temperatures. With subsequent heat-treatments a significant reduction of the β-phase is achieved. These outstanding features of TNM alloys distinguish them from other TiAl alloys which must exclusively be processed under isothermal conditions and/or which always exhibit a high fraction of β-phase at service temperature. After hot-working and multi-step heat-treatments, these alloys show yield strength levels > 800 MPa at room temperature and also good creep resistance at elevated temperatures.