bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isothermal Martensite Formation at Sub-Zero Temperatures
Authors: Stojko Allan , Hansen Mikkel F. , Slycke Jan , Somers Marcel A. J. 
Published: April 2011

Abstract
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

ABSTRACTSince 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

ABSTRACTRecently, 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

ABSTRACTHigh-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

ABSTRACTPerylene 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

ABSTRACTWe 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

ABSTRACTThin 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

ABSTRACTWith 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

ABSTRACTThe 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

ABSTRACTTemplate-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

ABSTRACTCu2ZnSnS4 (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

ABSTRACTWe 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

ABSTRACTWe 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

ABSTRACTNanocrystalline 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

ABSTRACTOur 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

ABSTRACTThe 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

ABSTRACTBiomolecules 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

ABSTRACTPolycrystalline 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

ABSTRACTLow 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

ABSTRACTOptimum 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.