bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nano structure formation by gas cluster ion beam irradiations at oblique incidence
Authors: Toyoda Noriaki , Yamada Isao 
Published: April 2011

ABSTRACTNano structure formations on Au surfaces by 20 keV Ar gas cluster ion beam (GCIB) irradiation at an oblique incidence were studied. When the incident angle was close to 0° from the surface normal of Au targets, the Au surface was smoothed due to the lateral sputtering effects and there were no structure formations on the surfaces. However, ripples were formed on Au surfaces at incident angle of 60° without sample rotation. When the Au samples were irradiated with Ar-GCIB at 60° with sample rotation, cone like structures with 50nm in diameters were fabricated and the surface roughness had a maximum value. However, the surface roughness suddenly decreased over incident angle of 60°. Even though the surface roughness was the same in the cases with and without sample rotations at 85° incidence, ripple structures were formed parallel to the incoming GCIB directions when there was no rotation. The incident angle dependence of the sputtering depth decreased following cosθ dependence. Very efficient surface smoothing without removing materials were realized with oblique incidence.
Irradiated Single Crystals for High Temperature Measurements in Space Applications
Authors: Volinsky Alex A. , Nikolaenko V. A. , Morozov V. A. , Timoshenko V. P. 
Published: April 2011

ABSTRACTWhile spacecrafts experience temperatures from -120 to 110°C on the orbit, their surface reaches extremely high temperatures, well above 1000 °C, during descent into the atmosphere due to aerodynamic heating. Sophisticated insulation systems are designed for thermal protection. One of the steps in designing a protection system is experimental temperature measurements.Neutron flux induces point defects formation and accumulation in diamond and SiC single crystals, which causes overall lattice expansion. During thermal annealing this process is reversed, so the annealing temperature and time result in the “reduced” lattice parameter (measured by X-Ray diffraction), which allows determining the maximum temperature, if the exposure time is known. This paper describes the use of irradiated single crystal high temperature sensors for measuring temperatures in thermal protection systems during spacecraft descent, as well as other space applications. These additional applications include measuring the furnace temperature during single crystal growth in space at zero gravity, and measuring the rocket combustion chamber turbo pump temperature.
Polymeric materials for Solar Sail: The combined effects of polymer thickness, radiation, and temperature
Authors: Edwards David L. , Chipara Mircea 
Published: April 2011

ABSTRACTThe feasibility and the performance of solar sail depend critically on the availability of light materials and extremely thin polymeric films. The main requirements imposed on solar sail materials are analyzed in depth. The potential effects of the space environment are discussed in detail, with emphasis on the radiation-temperature-polymeric film thickness relationships. It is shown that the radiation component of the space environment triggers two competing degradation processes (erosion and depolymerization) and that both processes act towards the decrease in the glass transition temperature.
Raman Spectroscopy for Carbon Based Amorphous Thin Films
Authors: Compagnini Giuseppe 
Published: April 2011

ABSTRACTVibrational spectroscopies and in particular Raman spectroscopy are known to be among the most useful tools to characterize and control the properties of carbon materials. This is because of the possibility to detect and study the carbon bonding state and because of the strong correlation between shape and width of the vibrational signals and the structure of the amorphous network. The aim of this work is to present some experiments in which the formation and evolution of carbon films obtained by energetic particle irradiation of solid targets or by deposition of carbonaceous species onto suitable surfaces, are controlled and studied by these methods. Particular attention will be given to pure amorphous carbon films and carbon based binary alloys.
Radiation-Induced Modifications in Polymeric Materials
Authors: Hui David , Chipara Magdalena D. 
Published: April 2011

ABSTRACTRadiation-induced modifications in polymeric materials are briefly reviewed. The attention is paid to the effect of ionizing radiation on the mechanical properties of polymers. The competition between several parallel degradation processes in the harsh conditions of the space environment is analyzed. The need for a complex analysis of the effect of polymeric materials in simulated space environments is demonstrated.
Molecular Self-Healing Processes in Polymers
Authors: Chipara M. , Wooley K. 
Published: April 2011

ABSTRACTA critical review of self-healing processes in polymers and composites based on polymeric matrices is presented. Two self-healing processes are analyzed, one “operating” within micron range and the other at molecular scale. Preliminary data on the molecular self-healing process in living polymers, as obtained by electron spin resonance are discussed. The possibility to develop a multi-scale self-healing material is suggested.
Luminescence and Upconversion Dynamics of Praseodymium in LiLuF4 Laser Crystals
Authors: Özen Gönül , Collins John M , Forte Ottavio , Meylman Misha , Abdulsabirov R. Yu , Bartolo Baldassare Di 
Published: April 2011

ABSTRACTWe have investigated the spectroscopic properties of Pr3+ ions in LiLuF4 laser host doped with 0.5% Pr3+ ions as a function of temperature. We obtained the luminescence spectra by exciting selectively the sample at 439nm into the 3P2 level and at 593nm into the 1D2 level. With excitation in the 3P2 level we obtained emission only from the 3P0 level but not from the 1D2 level at all temperatures between 24 and 300K. With excitation into the 1D2 level we observed the luminescence emitted by the same level and a strong blue up-conversion emission from the 3P0 level. We used the decay pattern inspection to assign spectral lines to specific radiative transitions and to study the dynamics of the excited ions in the crystal. Under direct excitation, the 1D2 decay curve is nonexponential at all temperatures, whereas the 3P0 decay is exponential only at low temperatures. The experimental data indicate that the 3P0 level is populated via upconversion due to mainly energy transfer.
Surface Modification of Polymers, Paints and Composite Materials Used in the Low Earth Orbit Space Environment
Authors: Kleiman Jacob I. 
Published: April 2011

ABSTRACTMany organic-based materials exposed to low Earth orbit (LEO) environment undergo dramatic changes and irreversible degradation of physical characteristics. While many protective schemes are used to reduce the effects of LEO environment, protection of such materials in LEO still remains a major challenge, especially for future long duration missions or space stations.In addition to the traditional protective coating approaches, surface modification processes were proposed and successfully used as an approach to protect polymers, thermal control paints and other components and structures from LEO environment. Among them two surface modification processes, the Photosil™ and the Implantox™ that used new approaches in silicon functionalization, as in the Photosil™, and a modified ion implantation process, as in the Implantox™ allowed to incorporate up to 36 at.% of Si into the upper surface layer regions of the treated polymers, composite materials, thermal control paints and other high-performance organic materials.The tests conducted in plasma and fast atomic oxygen (FAO) beam facilities at comparable to LEO fluencies (∼ (1–2)·1020 at.O/cm2 ) demonstrated erosion yields lower than −10−26 cm3at, unchanged thermal optical properties, where important, and excellent thermal match between the treated layers and the bulk of the treated materials. After FAO testing, the Implantox™ treated samples were clear and transparent, with a glassy-like shiny surface with no signs of any surface erosion.
Adhesion of Copper to Teflon ® poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) Surfaces Modified by Vacuum UV Photo-oxidation Downstream from Argon Microwave Plasma
Authors: Dasilva W. , Entenberg A. , Kahn B. , Debies T. , Takacs G. A. 
Published: April 2011

ABSTRACTGood practical adhesion of sputter-deposited Cu is achieved to poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) surfaces at short treatment times of vacuum UV (VUV) photo-oxidation downstream from Ar microwave (MW) plasma. Factors contributing to the adhesion include: (1) an improvement in wettability as observed by water contact angle measurements; (2) surface roughening; (3) defluorination of the surface; (4) cross-linking at the surface and (5) incorporation of oxygen as CF-O-CF2, CF2-O-CF2 and CF-O-CnF2n+1 moieties. With long treatment times, a cohesive failure occurred within the modified PFA and not at the Cu-PFA interface due to extensive chain scission weakening its mechanical properties.
Structural Characterization of Oxide layers on Aluminum Formed by Exposure to Hyperthermal Atomic Oxygen
Authors: Li Long , Wang Liang , Minton Timothy K. , Yang Judith C. 
Published: April 2011

ABSTRACTSingle crystal Al (100) was exposed to 5 eV atomic oxygen beam. The sample was maintained at a temperature of 220°C and the total atomic oxygen fluence was 8×1019 atom.cm-2. We have characterized the resulting oxide and interface structures by cross-sectional (scanning) transmission electron microscopy ((S)TEM) and scanning electron microscope(SEM). Our TEM results show that an amorphous aluminum oxide layer with ∼6 nm thickness formed on the aluminum crystal, and a rough alumina/Al(100) interface forms. For a systematic study of the evolution of the oxide, a unique Physical Sciences, Inc. Pitt FASTTM AO laser detonation atomic oxygen source in a UHV chamber is employed. The system is equipped with a Maxtek RQCMTM system, a research quartz crystal microbalance (QCM) with a dual-sensor head, to dynamically measure the mass change of an aluminum film coated on the sensor crystal during exposure to atomic oxygen. The Al film initially experiences mass loss, and then parabolic mass gain. To observe the structural evolution of the oxide, a very thin Al (100) single crystal was exposed inside the AO source, characterized by SEM and TEM. The surface morphology changed from flat to rough after 5.5 minutes of exposure. This surface roughening could be related to the initial mass loss measured by QCM.
The Development and Manufacture of Aluminium Mokumé Gane (Wood-Grain Metal) Decorative Alloy
Authors: Ferguson Ian T. , Derby Brian , Thompson G.E. 
Published: April 2011

ABSTRACTThe application of contemporary metallurgical knowledge and solid state bonding techniques provide for development of entirely new Mokumé Gane combinations. A multi-layered aluminium alloy is manufactured by the successive hot roll-bonding of two different aluminium alloys. The surface is then embossed with a selected pattern and machined back, exposing the various alloys. A range of suitable alloy combinations has been identified. When anodised, the surface presents the pattern as a strong contrast due to the differing anodising properties of the constituent alloy layers. The anodic coating can then be dyed with a wide range of colours to develop the decorative potential of the technique.
Optical Profilometry as a Non-Destructive Technique to Quantify Engraving on Medieval Brass Astrolabes
Authors: Newbury Brian D. , Notis Michael R. 
Published: April 2011

ABSTRACTOptical profilometry has been performed on an astrolabe dated 1556 AD and attributed to the famous maker Gualterus Arsenius of Louvain, Belgium. In this non-destructive technique, a beam of white light is impinged on the sample and combined with the chromatic aberration technique to accurately measure surface features. With machine parameters set to a vertical resolution of 0.1 μm, lateral resolution to 6 μm and a 3 mm depth of field, various engraving features on the astrolabe were studied. Both hand-scribed and stamped markings are present on the astrolabe components. Inspection of the hand-scribed date on the instrument's mater allows one to quantify the shape and dimensions of the tool used, as well as the direction and inclination of the engraving tool during inscription. The results of this analysis give information about how the astrolabe was constructed in one of the Renaissance's greatest scientific instrument workshops. The results are compared to similar engravings on an undated and unsigned Islamic astrolabe tympan.
Fiber Optics Reflectance Spectroscopy in the Entire VIS-IR Range: a Powerful Tool for the Non-invasive Characterization of Paintings
Authors: Bacci M. , Bellucci R. , Cucci C. , Frosinini C. , Picollo M. , Porcinai S. , Radicati B. 
Published: April 2011

ABSTRACTFiber optics reflectance spectroscopy (FORS) in the entire 380 – 11, 000 nm range has been used to non-invasively characterize Leonardo's paintingMadonna of the Yarnwinder. A preliminary analysis of the recorded spectra made it possible to obtain useful information concerning the pigments used, previous restoration work, the preparatory layer, and the binding medium. In particular, it was found that Thénard's blue was used in a previous restoration instead of the original ultramarine. As regards the painting technique, typical spectral features of oil binding medium are present in the mid-IR spectra, while near IR spectra reveal the occurrence of clay in the preparatory layer.
A Parametric Analysis of Relative Humidity Effects on Traditional Panel Paintings
Authors: Hagan Eric , Quasney Evan , Mecklenburg Marion 
Published: April 2011

ABSTRACTA finite element analysis was performed on panel painting structures subjected to changes in relative humidity. Measured Young's modulus values and humidity expansion coefficients were used to define the properties of materials characteristic to northern and southern European panels. Models of northern panels simulated white oak with two layers of oil paint, while models of southern panels simulated cottonwood with gesso and two oil paint layers. In both cases, the properties of the oil paints were input for lead white and Naples yellow respectively. Influence of radial/tangential grain orientation, panel thickness, and structural support were investigated through various humidity changes. Results are presented in the form of stress in the wood, gesso, and paint layers as well as curvature of the painted surfaces. Methods of reducing panel curvature with structural support are discussed, which involve applying a frictionless cradle, wood battens, or verso gesso layer. Verification of the model was performed with a derivation of general stress equations for a cradled painting with no friction between the slider-bars and the panel. A comparison of derived and parametric results confirms accurate behavior of the model.
Craft Knowledge as an Intangible Cultural Property: A Case Study of Samarkand Tiles and Traditional Potters in Uzbekistan
Authors: Vandiver Pamela B. 
Published: April 2011

ABSTRACTReverse engineering past craft technologies involves using the basics of materials science and engineering to a new end: their preservation and continuation. Examples are presented of the glazed tile technologies of Samarkand, Bukhara and other Silk Route cities of Uzbekistan that date from the thirteenth century A.D. but that continue to the present. The UNESCO charter for the preservation of Intangible Cultural Properties has enlightened the goals and results of the research and has linked together archaeological materials research and conservation science in an exciting new partnership.
Systematic Investigation of Exchange Coupling in Thickness Gradient Fe/Sm-Co and Co/Sm-Co Magnetic Bilayers
Authors: Yu M. H. , Hattrick-Simpers J. , Takeuchi I. , Liu J. P. 
Published: April 2011

ABSTRACTMagnetic bilayers Fe/Sm-Co and Co/Sm-Co have been fabricated with gradient thicknesses of the soft layers in order to systematically study the dependence of exchange coupling on the thickness of the soft layer. The films were deposited in a combinatorial magnetron-sputtering chamber, where the Fe and Co thickness wedges were created by the natural thickness gradient due to the deposition geometry. The soft layer was deposited at two different temperatures (150°C and 300°C) in order to study the effect of deposition temperature on the exchange coupling. The deposition of the Fe layer at the higher temperature (300°C) was found to enhance the interlayer exchange coupling between Fe and Sm-Co. The single-phase-like magnetization reversal critical thickness increases from 12 nm for Fe deposited at 150°C to 24 nm for Fe deposited at 300°C. We attribute the enhanced exchange coupling in Fe/Sm-Co bilayers to the interfacial mixing and the coherent growth of the Fe layer. On the other hand, we found that the exchange coupling between Co and Sm-Co is not sensitive to the growth temperature of the Co layer.
Magnetic and Transport Properties of Ferromagnetic-PEEK Polymer Nanocomposite Prepared via Ion-Implantation
Authors: Ghosh K. , Mishra S. R. , Losby J. , Kehl T. , Robertson B. , Kassim T. , Patel R. , Weigand M. , Curry M. , Giedd R. E. 
Published: April 2011

ABSTRACTThin films of magnetic-nanocomposite are prepared using a novel two step ion-implantation technique. Structural assessment via TEM of the ion bombarded iron-polymer composite shows development of fine magnetic nanoparticles (20–50 A) in a carbonaceous matrix. The experimental temperature dependence of conductivity of the composite, in the temperature range 10–300 K, follows the exponential law σ = σo exp [(-To/T)γ], where To and γ are constants. The observed higher values of γ > 1 imply the presence of more than one conducting channel in the composite. The secondary conducting channels, beside hopping conductivity, may arise from the conducting graphitic matrix around Fe nanoparticles. The room temperature magneto-transport measurement indicates a 0.5% change in magnetoresistance at 0.5T field. The observed anomalous Hall voltage confirms the presence of magnetic nature of nanoparticles.
Effects of defects on the electrical and magnetic properties of Ga1−x MnxAs layer
Authors: Koh D. , Park J.-B. , Park Y. J. , Lee J. I. , Park C. , Cho H. , Kim Y. M. , Park I.-W. , Chung K. S. 
Published: April 2011

ABSTRACTWe investigated the effects of V/III flux ratios on the Curie temperature, TC, in Ga1−x Mnx As layers with various Mn mole fractions of x = 0.03 and 0.05. A 75 nm thick GaMnAs layer was grown at the temperature of 250 °C with various V/III flux ratios of 25∼34. The low temperature molecular beam epitaxy (LT-MBE) method for growth of GaMnAs layer caused the defects related by excess As and Mn interstitial, and these leaded the formation of deep level. We investigated that formation of deep level was established with various Mn mole fraction for V/III flux ratio 34. The changes of TC are observed by varying V/III flux ratio with a fixed Mn mole fraction. The TC in the sample grown with a lower V/III flux ratio of 25 is found to be higher comparing to that with higher V/III flux ratio of 34 at a fixed high Mn concentration (x = 0.05). Although the Mn concentration increases, the TC is not much changed when the V/III flux ratio is high of 34. The changes of TC with various V/III flux ratios are explained by the existence of low temperature grown defects, which are clarified by the deep level transient spectroscopy measurement. The prime species of defects are found to be AsGa and MnI etc.
In-Situ Magnetic Field Induced Structure and Properties of Epitaxial Spinel Ferrite Thin Films Prepared by Pulsed Laser Deposition (PLD) (Dynamic Aurora PLD Method)
Authors: Wakiya Naoki , Nagamune Toyokazu , Shinozaki Kazuo , Mizutani Nobuyasu 
Published: April 2011

ABSTRACTThe influence of an in-situ magnetic field on the plume during pulsed laser deposition (PLD) to prepare epitaxial nickel zinc ferrite (NZF) thin films were investigated. An air core coil (solenoid coil) was installed between a target and a substrate, and up to 43 mT of magnetic field was generated by direct current (DC)(Dynamic Aurora PLD method). Application of magnetic field brought about following structural and property changes;(1) deposition rate was almost doubled, (2) the concentration of Ni and Zn in the film was decreased, (3) lattice parameter was unchanged, and (4) magnetization and coercivity was increased. Since deposition rate was increased by application of magnetic field, films with same thickness was also prepared without magnetic field, however, magnetic properties were unchanged. This indicates that application of in-situ magnetic field improved magnetic properties.
Magnetophotonic Crystals
Authors: Inoue Mitsuteru 
Published: April 2011

ABSTRACTWhen the constitutive materials of photonic crystals (PCs) are magnetic, or even only a defect in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical (MO) properties: The strong photon confinement in the vicinity of magnetic defects results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of magnetization in media, and hence they are called magnetophotonic crystals (MPCs) providing the spin-dependent nature in PCs.
Controlling (In, Ga)As quantum structures on high index GaAs surfaces
Authors: Seydmohamadi Sh. , Wen H. , Wang Zh. M. , Salamo G. J. 
Published: April 2011

ABSTRACTWe investigate the formation of (In, Ga)As self assembled quantum structures grown on different orientations of a GaAs substrate along one side of the stereographic triangle between (100) and (111)A surfaces. The samples were grown by Molecular Beam Epitaxy, monitored by Reflection High-Energy Electron Diffraction during the growth and characterized by in-situ Scanning Tunneling Microscopy and Atomic Force Microscopy. A systematic transition from zero dimensional (In, Ga)As quantum dots to one dimensional quantum wires was observed as the substrate was varied along the side of the triangle within 25° miscut from the (100) toward (111)A, which includes several high index surfaces. We propose an explanation for the role of the substrate in determining the type of the nanostructure that is formed.
The Effects of Nanoscopic Fillers on the Viscoelastic Response of Polymers
Authors: Xavier Jean Harry , Sokolov J. , Rafailovich M.H. 
Published: April 2011

ABSTRACTWe have used a technique developed by Brochard (Macromolecules, 2004, 37, 1470) using free standing thin films to study the viscoelastic response of filled-polymer films. Transmission Electron Microscopy (TEM) experiments reported that fillers were well distributed within the films, and therefore no clustering and interfacial segregation occurred. Results from Shear Modulation Force Microscopy (SMFM) measurements revealed that the glass transition temperature of the polymer (Tg) was depressed by 10°C relative to the bulk for Au (10 nm), and bulk like for Au (3 nm). The effects of colloidal fillers on the tracer diffusion coefficient (D) were studied using secondary ion mass spectrometry (SIMS), and results found that D was increased significantly for the Au 10 nm, and constant for the Au 3 nm. Values for zero shear rate viscosity extracted from the diffusion coefficient were compared to the shear strain calculated from the hole growth measurements, and theoretical predictions. Results were attributed to an increase in excluded volume when large particles were introduced into the matrix.