bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Rare Earth Niobate Buffer Layer for YBCO Coated Conductor Using Chemical Solution Deposition Approach
Authors: Bhuiyan M.S. , Paranthaman M. , Sathyamurthy S. 
Published: June 2019

AbstractWe have grown epitaxial rare earth niobate (RE3NbO7; RE – La, Ce, Nd, Sm, Eu, Gd, Ho, Y, and Yb) buffer layers on biaxially textured Ni-W substrates using chemical solution deposition approach. Precursor solutions of 0.4 M total cation concentration were spin coated on short samples of Ni-3 at.%W (Ni-W) substrates and heat-treated at 1050 to 1100°C in a gas mixture of Ar-4%H2 for 15 minutes. Effect of solution chemistry and processing atmosphere on texture and microstructure were studied. Detailed X-Ray studies indicated that all the rare earth niobates were grown epitaxially. There was no significant change observed in texture for different precursor chemistry, however, dramatic effect on surface morphology observed. SEM and AFM investigations of RE3NbO7 films reveal noticeable difference in surface morphology and roughness for various processing atmospheres. Processing under a 20% wet Ar-4% H2 gas mixture was found to be the optimum condition for growing Gd3NbO7 films with high quality microstructure.
Interface Control in All MOD Coated Conductors: Influence on Critical Currents
Authors: Pomar Alberto , Coll Mariona , Cavallaro Andrea , Gàzquez Jaume , Mestres Narcis , Sandiumenge Felip , Puig Teresa , Obradors Xavier 
Published: June 2019

AbstractIn this work we will report our recent progress in the control of the interface quality between buffer layers and YBCO thin films grown by the trifluoroacetates route (TFA) and how it influences the critical current of the coated conductors. We have mainly focused on vacuum and metalorganic deposited (MOD) fluorite-like CeO2 buffer layers and on MOD perovskite SrTiO3 buffer layers. We will show that for vacuum CeO2 buffer layers, microcracks at the surface can be controlled by the means of thermal treatments. Coated conductors TFA-YBCO/CeO2sputt/YSZ/CeO2/Ni with Jc(77K)˜1MA/cm2 can be grown even in the presence of these microcracks. For MOD SrTiO3 we will show that growing the buffer layer at low temperature reduces surface roughness and multilayers with high critical currents can be achieved. An all-chemical coated conductor has been grown TFA-YBCO/SrTiO3MOD/BaZrO3MOD/NiO-SOE/Ni with promising in-plane texture, Δ φYBCO=6.6°. For MOD CeO2 buffer layers, thermal annealings in oxidizing atmospheres lead to atomically flat surfaces that avoid the typical polycrystalline surfaces observed in MOD CeO2 grown in Ar/H2. High Jc multilayers can be achieved and the first all chemical coated conductor in IBAD tapes TFA-YBCO/CeO2MOD/YSZIBAD/SS has been obtained with Jc(60K)=2.3MA/cm2.
High-k Polymerized Dichlorotetramethyldisiloxane Films Deposited by Radio Frequency Pulsed Plasma for Gate Dielectrics in Polymer Field Effect Transistors
Authors: Xu Yifan , Berger Paul R. , Cho Jai , Timmons Richard B. 
Published: June 2019

AbstractPolymerized dichlorotetramethyldisiloxane (DCTMDS) films deposited by radio frequency pulsed plasma polymerization (PPP) demonstrated very high dielectric constants for an organic-based system, in the range of 7 to 10. The high dielectric constants of PPP DCTMDS films are due to the high polarizability of the DCTMDS monomer. The pulsed plasma duty cycle (ON/OFF) resulted in higher dielectric constant DCTMDS films for higher duty cycles. The variation of dielectric constants does not show any trend with varying film thicknesses, indicating that the thickness of the deposited films is not significant for controlling permittivity. Post-deposition annealing in a certain temperature range improves the electrical integrity of PPP DCTMDS films, but temperatures that are too high induce even higher leakage than the samples with no heat treatment. An optimal annealing temperature was identified to be in the range of 150 °C to 200 °C. Samples annealed within this temperature window have low leakage current densities below 0.1 pA/νm2 at 10 V for film thicknesses about 100 nm. The PPP DCTMDS films are resistant to typical chemical solvents, and have withstood conventional photolithographic processing with no observable film shrinkage, warping or peeling. Film adhesion was excellent and withstood the scotch tape test.
Selective Nucleation and Growth of Large Grain Polycrystalline GaAs
Authors: Allen C. G. , Beach J. D. , Khandekar A. A. , Dorr J. C. , Veauvy C. , Collins R. T. , Kuech T.F. , Caputo R. M. , Hollingsworth R. E. , Inoki C. K. , Kuan T. S. 
Published: June 2019

AbstractA method for depositing large grained polycrystalline GaAs on lattice mismatched substrates through controlled nucleation and selective growth is presented. The process was developed on Si wafers. Nucleation site formation began with nanolithography to create submicron holes in photoresist on Si. Ga metal was electrochemically deposited into the holes. Subsequent arsine anneals converted the gallium deposits into GaAs. Photoluminescence and electron diffraction verified conversion to GaAs. Metal-Organic Chemical Vapor Deposition (MOCVD) enlarged the seed crystals to coalescence without creating additional nucleation sites within the patterned field. Having successfully demonstrated the approach, subsequent work has been directed at lower cost, alternative ways to define initial nucleation sites, such as, microcontact lithography and direct decomposition of triethyl gallium to Ga metal in the MOCVD chamber.
Direct Patterning of Molecular Organic Materials and Metals Using a Micromachined Printhead
Authors: Chen Jianglong , Leblanc Valérie , Kang Sung Hoon , Baldo Marc A. , Benning Paul J. , Schmidt Martin A. , Bulović Vladimir 
Published: June 2019

AbstractMicron-scale lateral patterning of molecular organic thin films is still one of the most challenging issues in the practical fabrication of pixelated organic light emitting device (OLED) displays. In this work we demonstrate organic and metal thin film patterning using a micromachined printhead that modulates the vapor flux of evaporated materials incident on a substrate. The printhead is integrated with an x-y-z manipulator that facilitates patterning within a vacuum environment at pressure of less than 5×10-6 Torr. This printing scheme enables direct, solvent-free and mask-free patterning of organic optoelectronic devices on diverse substrates. As an example we fabricated an OLED array of 30×30 νm Alq3 (tris(8-hydroxyqunolinato) aluminum) pixels. 30 νm wide silver patterns were also directly written using the same technique. The results show that this printing method is capable of patterning molecular organic materials and metals at high resolution (800 dpi).
Lateral Nonuniformity And Mesoscale Effects in Giant Area Electronics
Authors: Karpov V. G. , Shvydka Diana , Roussillon Yann 
Published: June 2019

AbstractThe recently developed physics of thin-film photovoltaics is suggested to be representative of other giant area electronics. We show that (i) giant-area devices are intrinsically nonuniform in the lateral directions, (ii) the nonuniformity spans length scales from millimeters to meters depending on external drivers such as light intensity and bias, and (iii) it significantly impacts the device performance. We derive a fundamental length scale that discriminates between the cases of small and large-area devices, and beyond which a new physics emerges. In addition, we present a practical method of mitigating the nonuniformity effects.
A novel patterning technique for high-resolution RGB-OLED-displays: Laser induced local transfer (LILT)
Authors: Kröger Michael , Hüske Marc , Dobbertin Thomas , Meyer Jens , Krautwald Henning , Riedl Thomas , Johannes Hans-Hermann , Kowalsky Wolfgang 
Published: June 2019

AbstractA novel patterning technique for high-resolution full-color OLED-displays will be discussed. Currently applied production systems for OLED-displays incorporate a shadow masking system for patterning of single red, green and blue pixels. Due to its limited scalability, alternative techniques, which can be applied to larger substrate sizes, have to be developed. One approach can be the laser induced local transfer of organic materials.An infrared absorbing substrate (target) is coated with either a red, green or blue light-emitting organic material and placed in a short distance (below 50 νm) of the OLED-substrate onto which the organic material is to be patterned. The laser beam is deflected by a scanner onto the target in single lines. If the scanning speed and the laser power are adjusted properly, the target locally heats up to a temperature at which the organic material sublimes and condenses on the opposing OLED-substrate. By repeating this process for each colour red, green and blue stripes can be deposited. Line widths below 70 νm have been achieved.
Effect of Age-Induced Transparency on the Mechanical Properties of Human Dentin
Authors: Nalla Ravi K. , Kinney John H. , Pople John A. , Breunig Thomas M. , Tomsia Antoni P. , Ritchie Robert O. 
Published: June 2019

AbstractMost non-traumatic fractures occur in teeth that have been treated, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of altered forms of dentin. One such altered dentin is transparent (sclerotic) dentin, which forms gradually with aging. Accordingly, in the present study, we seek to study differences in the structure, i.e., dentinal mineral concentration, mineral crystallite size, and the mechanical properties, i.e., elastic moduli, fracture toughness and fatigue behavior, of normal and transparent root dentin. The mineral concentration, measured by x-ray computed tomography, was found to be significantly higher in transparent dentin, with the majority of the increase being due to the closure of the tubule lumens. Crystallite size, as measured by small angle x-ray scattering, appeared to be slightly reduced in transparent dentin, although the difference was not statistically significant. The elastic properties remained unchanged, although transparent dentin showed almost no yield/post-yield behavior. The fracture toughness was lowered by roughly 20%, while the fatigue resistance was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent dentin.
Quantitatively Studying Nano-mechanical Properties within the Prism and Organic Sheath of Enamel
Authors: Cui Fuzhai , Ge Jun , Wang Xiumei 
Published: June 2019

AbstractEnamel is made up of enamel prisms separated by thin layer of organic sheaths. The mechanical properties of the prisms and the organic sheaths are obviously different from each other due to different compositions and microstructures. However, quantitative measurements of such differences have been a challenge in the past. The objective of this study is to accurately study the mechanical properties in the isolated domains within single enamel prism. The technique of nanoindentation combined with Atomic Force Microscopy (AFM) was employed to test the enamel specimens from mature human maxillary third molar. It was revealed that the nanohardness and elastic modulus of the sheaths were about 73.6% and 52.7% lower than those of the prisms. AFM topographies of the residual indent impressions also visually confirmed the differences. In addition to nanoindentation tests, the microstructures of enamel were carefully investigated in terms of hierarchical levels of organization to understand the structural reasons of the mechanical differences. We found a close relation between the variations of mechanical properties of enamel and its hierarchical structure. The analysis of the mechanical properties within enamel upon hierarchy is not only helpful to understand its unique property, but may also inspire ideas for the design of novel synthetic materials.
Protein Forced Unfolding and Its Effects on the Finite Deformation Stress-Strain Behavior of Biomacromolecular Solids
Authors: Jerry Qi H. , Ortiz Christine , Boyce Mary C. 
Published: June 2019

AbstractMany proteins have been experimentally observed to exhibit a force-extension behavior with a characteristic repeating pattern of a nonlinear rise in force with imposed displacement to a peak, followed by a significant force drop upon reaching the peak (a “saw-tooth” profile) due to successive unfolding of modules during extension. This behavior is speculated to play a governing role in biological and mechanical functions of natural materials and biological networks composed of assemblies of such protein molecules. In this paper, a constitutive model for the finite deformation stress-strain behavior of crosslinked networks of modular macromolecules is developed. The force-extension behavior of the individual modular macromolecule is represented using the Freely Jointed Chain (FJC) statistical mechanics model together with a two-state theory to capture unfolding. The single molecule behavior is then incorporated into a formal continuum mechanics framework to construct a constitutive model. Simulations illustrate a relatively smooth “yield”-like stress-strain behavior of these materials due to activate unfolding in these microstructures.
Raman Spectroscopic Evidence for Side-Chain Unfolding in Spider Dragline Silk under Tensile Deformation
Authors: He Xiaojun , Ellison Michael S. , Palmer Jacqueline M. 
Published: June 2019

AbstractIn-situ Ramanspectra were collected on the N. clavipes spider dragline silk under a tensile deformation rate of 15mm/min. The most prominent features on the spectra were due to those bands near 1100 cm-1, which present as a sensitive probe to structural changes associated with side-chains of silk peptide. A downshift of Raman bands at 1095 cm-1 and 1089 cm-1 was detected with increasing strain. Furthermore, an increase in the intensity of the Raman band at 1062 cm-1 due to the vibration of trans structure without lateral coupling was prominent at certain strain levels. This was interpreted in terms of a morphology transition from the random configuration to the trans conformation modulated by the reorganization of the hydrogen bonding among the side-chain.
Modeling and characterization of the amino propeptide of collagenα1(XI), a regulatory domain in collagen fibrillar architecture.
Authors: Warner Lisa R. , Fallahi Arzhang , Kroll Becky , Irwin Katey M. , Yingst Sorcha , Mercer Linda M. , Shadle Susan E. , Oxford Julia Thom 
Published: June 2019

AbstractConnective tissues such as cartilage, tendon, skin, bone, and arteries are composite bio-materials that contain predominantly water, collagen, proteoglycans and hyaluronic acid. Like any composite material, the components themselves and their interactions dictate the properties of the material. Fibrillar collagens are the principal structural molecules of the connective tissues and require regulated assembly and growth. Previous work from our lab indicates that the amino propeptide (Npp) domain of collagen type XI α1 chain regulates fibril diameter growth. Npp is a globular domain that is thought to sterically hinder the dense packing assembly of collagen molecules in fibrils. This mechanism of regulating collagen fibril assembly may be more complex than steric hindrance. We hypothesize that the Npp domain has a more dynamic role in establishing the structure/function relationship of collagen fibrils in connective tissues. In this study, the molecular structure of Npp was predicted by modeling. The model predicted putative binding sites for heparan sulfate and divalent cations. These predicted binding sites were evaluated empirically by fluorescence spectroscopy and surface plasmon resonance.
Structure and Properties of Murine and Human Dentin
Authors: Habelitz Stefan , Zartoshtimanesh Shabnam , Balooch Mehdi , Marshall Sally J. , Marshall Grayson W. , DenBesten Pamela K. 
Published: June 2019

AbstractMice are commonly considered the model mammal for many biomedical studies. In this work, mouse and human dentin were compared to specify structural and mechanical differences to establish a baseline for comparison of dental tissues between these species. Atomic force microscopy revealed tubules of about 1.0 to 1.6 μm in diameter as the main structural feature in dentin of both species. Nanoindentation yielded the elastic modulus about 15% lower in murine intertubular dentin while the hardness was almost equal. Dynamic stiffness mapping confirmed the lower elastic properties and also revealed that the peritubular region of increased mineralization around tubules is drastically reduced or maybe absent in murine dentin of this age. This study suggests that structural and mechanical differences need to be considered when murine dentin is used as a model system.
Mesostructure of the Exoskeleton of the Lobster Homarus Americanus
Authors: Raabe D. , Romano P. , Al-Sawalmih A. , Sachs C. , Servos G. , Hartwig H.G. 
Published: June 2019

AbstractThe exoskeleton of the lobsterHomarus americanusis a multiphase bio-composite which consists of a fibrous organic matrix (crystalline α-chitin and various types of non-crystalline proteins) and embedded biominerals (mainly calcite). In this study we present experimental data about the microscopic and mesoscopic structure of this material.
Influence of Cross-linking and Oxidation on the Microstructural Mechanical Properties of UHMWPE
Authors: Roy Marcel E. 
Published: June 2019

AbstractUltra-high molecular weight polyethylene (UHMWPE) is commonly used as a bearing surface in total joint replacements. This study examined the effects of cross-linking and oxidation on the mechanical properties of UHMWPE at the microstructural level, rather than at the bulk level. Nanoindentation tests were performed on the articulating surfaces of two freshly machined UHMWPE acetabular inserts, one of which was cross-linked, and also performed along a freshly cut cross-section of a UHMWPE tibial insert that had been sealed in its original packaging and shelf-aged for at least five years. The reduced modulus of cross-linked UHMWPE was significantly lower than native UHMWPE. Tests on the cross-section of the shelf-aged specimen revealed a reduced modulus profile with a subsurface peak that was similar to the oxidation profiles of aged UHMWPE observed by others. Future work should examine the microstructural mechanical properties of UHMWPE using methods that more accurately account for its viscoelastic nature, and should directly correlate microstructural properties with oxidation.
Three-Dimensional PEG Hydrogel Construct Fabrication using Stereolithography
Authors: Arcaute Karina , Ochoa Luis , Medina Frank , Elkins Chris , Mann Brenda , Wicker Ryan 
Published: June 2019

AbstractLayered manufacturing (LM) using stereolithography (SL) of aqueous polymer solutions was accomplished so three-dimensional (3D) tissue engineered scaffolds with complex distributions of bioactive agents could be produced. Successful LM with embedded channel architectures required investigation of hydrogel thickness or cure depth as a function of photoinitiator type and concentration, energy dosage, and polymer concentration in solution. Poly(ethylene glycol) dimethacrylate (PEG-dma) with an average molecular weight of 1000 in quantities of 20% and 30% (w/v) was prepared in distilled water. Different concentrations of two photoinitiators (PIs), Sarcure1121 (2-hydroxy-2-methyl-1-phenyl-1-propanone) and Irgacure 2959 (2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone), were used to vary gel thickness at select energy dosages by controlling the scan speed of the SL machine's ultraviolet scanning system. Gel thickness was a strong function of PI type and concentration, energy dosage, and PEG-dma concentration, especially at the low PI concentrations required for implantation. The gel thickness curves were utilized to demonstrate LM for two construct geometries where different layer thicknesses were required to successfully fabricate the constructs. This work demonstrates the effective use of SL as a processing technique for complex 3D tissue scaffolds and addresses some practical considerations associated with the use of hydrogels in LM.
Investigations on Multi-axial Domain Switching Criteria for Piezoceramics
Authors: Laskewitz Bernd , Zhou Dayu , Kamlah Marc 
Published: June 2019

AbstractInitially unpoled soft PZT was subjected to a proportional, coaxial electromechanical loading. The ratio of compressive stress to electric field was changed between the experiments. From this series of nonlinear polarization and strain responses were obtained. Based on an offset method, initial domain switching states in the two-dimensional stress-electric field space were determined. In continuum mechanics, thin walled tubes are used to investigate multi-axial stress states. In this context, thin walled means a ratio of wall thickness to radius of 1:10 or thinner. However, simple linear dielectric analysis indicates an inhomogeneous electric field distribution in such geometries.Therefore, the suitability of hollow cylinders (in the range from thick to thin walled tubes) for multi-axial electromechanical experiments has to be investigated. Simulations with a finite element tool based on a phenomenological constitutive model for ferroelectric and ferroelastic hysteresis behavior were performed. The results confirm inhomogeneous distributions of electric fields and stresses after poling. A geometry variation is discussed to minimize these effects.
A Free Energy Model for the Inner Loop Behavior of Pseudoelastic Shape Memory Alloys
Authors: Heintze Olaf , Seelecke Stefan 
Published: June 2019

AbstractThe paper presents a free energy model for the pseudoelastic behavior of shape memory alloys. It is based on a stochastic homogenization process, which uses distributions in energy barriers and internal stresses to represent effects typically encountered in polycrystalline materials. This concept leads to a realistic desription of the rate-dependent inner loop behavior, but is characterized by rather long computation times. This is prohibitive in regard to a potential implementation into other numerical codes, such as finite element or optimal control programs or a Matlab/Simulink environment. For this purpose a parameterization method is introduced, which is derived from the concept of a representative single crystal. The approach preserves the desirable properties of the original formulation, at the same time reducing the numerical effort significantly. Finally, we show that the method can reproduce the experimentally observed behavior accurately over a large range of strain rates including the minor loop behavior.
A Stress-Dependent Hysteresis Model for PZT
Authors: Ball Brian L. , Smith Ralph C. , Kim Sang-Joo , Seelecke Stefan 
Published: June 2019

AbstractThis paper addresses the development of an energy-based characterization framework which quantifies stress-induced dipole switching in ferroelectric materials. Helmholtz and Gibbs energy relations that accommodate 90° and 180° dipole orientations as equilibrium states are constructed at the lattice level. For regimes in which thermal relaxation mech- anisms are negligible, minimization of the Gibbs relations provides local polarization and strain relations. Alternatively, behavior such as creep or thermal relaxation can be incorpo- rated by balancing Gibbs and relative thermal energies through Boltzmann principles. In the nal step of the development, stochastic homogenization techniques based on the assump- tion that parameters such as coercive and induced elds are manifestations of underlying distributions are employed to construct macroscopic models suitable for nonhomogeneous polycrystalline compounds. Attributes and limitations of the model are illustrated through comparison with experimental PLZT data.