bluuebunny/crossref_metadata_2025_split huggingface dataset:
In situ SAXS/XRD on mesoscopically ordered surfactant-silica mesophases; What can we learn?
Authors: Lindén Mika , Teixeira Cilaine V. , Amenitsch Heinz , Alfredsson Viveka , Kleitz Freddy 
Published: April 2011

ABSTRACTIn situ investigations have proven to be a very useful means of understanding the different processes involved in the formation of mesoporous materials. In this communication, we demonstrate the potential of in situ small angle x-ray scattering, SAXS and x-ray diffraction, XRD, measurements for giving both qualitative and quantitative results on the structural evolution during the early stages of the surfactant-silicate composite formation. The examples given are based on results obtained for 2D hexagonal structures, synthesized both under acidic and alkaline conditions. Careful analysis of both the scattering and diffraction patterns allows the different stages of the formation to be described in some detail. Thus, new synthesis approaches can be foreseen that allow the structure of the final hybrid mesophase to be rationally controlled.
Fabrication of Nanocomposite Thin Film of Hydroxyapatite and Polyvinylalcohol and its Ionic Conductive Properties
Authors: Takaki Toshihiko , Fukuda Kazuyuki , Tajitsu Yoshiro 
Published: April 2011

ABSTRACTA hydroxyapatite (HAp)-polyvinylalcohol (PVA) nanocomposite was prepared by the in-situ method. When the HAp was synthesized by reacting Ca(OH)2 with H3PO4 in the presence of PVA having carboxyl groups, the interaction between the carboxylic groups of PVA and calcium ions of HAp led to the formation of nanometer-sized spindle HAp particles (long axis ca. 80 nm and short axis ca. 25 nm). The reactant was stable and formed transparent thin films by the casting method. Nanometer-sized HAp particles were uniformly dispersed in PVA film. Properties of the HAp-PVA nanocomposite film, such as tensile strength, gas barrier, and pencil hardness, were superior to those of the pure PVA. Furthermore, the nanocomposite film had high ionic conductivity compared to pure PVA and traditional composite. The ionic conductivity of the stretched film (PVA: HAp = 1:1) with 35wt % content of LiN(CF3SO2)2 was about 10-3 S/m at room temperature. Regarding the mechanism of this study, we believe that the HAp particles play a crucial role in increasing the free lithium cations to accelerate the ionic conductivity, according to the ionic interaction on the HAp surface.
Morphology and Polymorph Selectivity Control in Calcium Carbonate Mineralization
Authors: Sindhu Swaminathan , Ajikumar Parayil K. , Jegadesan Subbiah , Valiyaveettil Suresh 
Published: April 2011

ABSTRACTThe present paper describes the mineralization of calcium carbonate at a low temperature (4 °C) and in presence of additives. Aspartic acid immobilized polyacrylic acid (PA-Asp) induced the nucleation of spherical vaterite polymorph at 4 °C. But at room temperature, a thin film of calcite was deposited. Moreover, stable amorphous calcium carbonate was precipitated in presence of magnesium at low temperature. The observed results show that low temperature and presence of additives influence the nucleation, polymorph selectivity and morphology of the precipitated calcium carbonate.
Real-time observation of ion beam eroded silicon surfaces: Ripple propagation, coherence and noise effects in surface erosion
Authors: Habenicht S. , Lieb K. P. 
Published: April 2011

AbstractThe evolution of ion beam eroded Silicon surfaces was measured in real-time by combining focused ion beam technology with scanning electron microscopy. By detecting the secondary electrons emitted during implantation the surface was monitored in-situ during the erosion process of a Gallium focused ion beam. Repetitive scanning of the ion beam over the surface effectuates a coherent erosion of the exposed surface area, with the continuum theory of erosion as the ergodic limitation. Surface ripple as proposed by linear erosion theory were observed for oblique incidence of the ion beam and their propagation with progressing erosion time as well as their velocity dispersion were monitored. The ripple wavelength has been observed to increase with the erosion time and the value of the ripple velocity was observed to agree qualitatively with the results of Monte-Carlo simulations of the erosion process.Noise effects acompanying the erosion process are found to be responsible for the reorientation of the ripples when the orientation of the ion beam onto the surface is varied. This mechanism is discussed to stimulate further efforts in this field of surface erosion.
Nanostructure analysis of protein thin film prepared by wet and dry processes
Authors: Taketani I. , Nakayama S. , Nagare S. , Senna M. 
Published: April 2011

ABSTRACTSilk fibroin (SF) and bovine serum albumin (BSA) thin films were deposited on Si(100) substrate either by colloid casting method or by pulsed laser deposition (PLD). Emphasis is laid on the comparison of nanostructures, which developed during the deposition. AFM diagrams were evaluated to quantify the nanostructures, parallel and perpendicular to the substrate, by the average wavelength of the profilogram (Wa ) and surface roughness (Rrms ), respectively. The film thickness increased with increasing the concentration of colloids or laser deposition time. The value of Wa increased with the film thickness. We note, however, that the value Wa becomes much less sensitive with decreasing the scanning area due to decreasing probability of the abnormally large agglomerates of the nanometric units. Probability of the agglomeration growth as a consequence of the surface adhesion is higher with higher concentration of random coil, followed by β-sheet and α-helix. BSA with smaller primary units and lower probability of agglomeration give more uniform films.
The Stress Driven Rearrangement Instabilities in Electronic Materials and in Helium Crystals
Authors: Grinfeld Michael , Grinfeld Pavel , Kojima Haruo , Little John , Masutomi Ryuichi , Persson Per-Olof. , Zheleva Tsvetanka 
Published: April 2011

ABSTRACTAt present, there is a consensus that various Stress Driven Rearrangement Instabilities (SDRI) are the implications of the mathematically rigorous theoretical Gibbs thermodynamics. Many applied researchers and practitioners believe that SDRI are also universal physical phenomena occurring over a large range of length scales and applied topics. There is a multitude of publications claiming experimental observation of the SDRI based phenomena. This opinion is challenged by other highly respected scholars claiming theoretical inconsistencies and multiple experimental counterexamples. Such an uncertainty is too costly for further progress on the SDRI topic. The ultimate goal of our project is to resolve this controversy.The project includes experimental, theoretical, and numerical studies. Among various plausible manifestations of SDRI, the authors focused only on two most promising for which the validity of the SDRI has already been claimed by other researchers: a) stress driven corrugations of the solid-melt phase interface in macroscopic quantum 4He and b) the dislocation-free Stranski-Krastanov pattern of growth of semiconductor quantum dots. We devised a program and experimental set-ups for testing applicability of the SDRI mechanisms using the same physical systems as before but using implications of the SDRI theory for 2D patterning which have never been tested in the past.
Mechanisms of Cu<111> Columns Growth
Authors: Wang Jian , Huang Hanchen 
Published: April 2011

ABSTRACTThe Cu <111> columns, which are formed during magnetron sputtering deposition, are faceted on the top and zigzag on sides. Our numerical results of large facet-facet diffusion barriers offer an explanation of the facet dimension. Based on the stacking fault formation energies of various face-centered-cubic metals, we suggest that the zigzag shape of Cu <111> columns is a result of deposition twins. Our molecular dynamics simulations indeed confirm this suggestion. Further, the dynamics simulations reveal the transient role of {100} facets, which facilitate the formation of {111} facets and disappear afterwards.
Multiscale Phenomena in Bruggeman Composites
Authors: Skomski Ralph , Li Jiangyu , Zhou Jian , Sellmyer David J. 
Published: April 2011

ABSTRACTMechanical, magnetic, and transport properties of arbitrary inhomogeneous composites are investigated by a Bruggeman-type mean-field approach. The theory yields materials parameters as functions of the volume fractions, geometries, and materials constants of the phases. Each system is described by a single response parameter g, which is equal to the percolation threshold of the composite. For macroscopic systems, the approach yields very simple expressions, but nanoscale and multiferroic effects yield relatively complicated corrections to g. In the respective cases, the parametergdepends on the length scale of the composite and has the character of a combination of magnetic, electric, and mechanical degrees of freedom.
Processing and Development of a New High Strength Metal Foam
Authors: Rabiei A. , O'Neill Adrian T. , Neville Brian P. 
Published: April 2011

ABSTRACTThe research sited in this paper involves the development of new closed cell metal foam composite materials using powder metallurgy (PM) and gravity casting techniques. The foam is comprised of steel hollow spheres packed into a random dense arrangement, with the interstitial space between spheres occupied with a solid metal matrix. Using a casting technique, an aluminum alloy infiltrates the interstitial spaces between steel spheres. In a powder metallurgy method, steel spheres and iron powder are sintered to form a solid, closed cell structure. The measured densities of the Al-Fe composite foam and iron foam are 2.4 g/cm3 and 3.2 g/cm3, with relative densities of 42% and 41% respectively.The hollow sphere metal foam composite materials developed in this study displayed superior compressive strength as compared to hollow sphere foams currently being produced. The compressive strength of the cast Al-Fe foam averaged 67 MPa over a region of 10 to 50% strain, while the steel PM foam averaged 45 MPa over the same strain region. Densification began at approximately 50% for the cast foam and 55% for the PM foam.
Formation of boron carbonitride nanotubes from in situ grown carbon nanotubes for space applications
Authors: Piazza F. , Nocua J. E. , Hidalgo A. , De Jesús J. , Velázquez R. , Morell G. 
Published: April 2011

ABSTRACTBoron carbonitride nanotubes (BCNNTs) were grown with high yield by arc discharge without catalyst particles or pre-grown template nanostructures. Two types of nanotubes (NTs) were formed: thin NTs with diameters of 10–15 nm and thick NTs with diameters of 25–50 nm, all multiwall. Transmission electron microscopy, electron energy loss spectroscopy, and Raman spectroscopy analyses indicate that the thin NTs are carbon NTs (CNTs) while the thick NTs are BCNNTs wrapped around CNTs. The growth kinetic appears to be faster for CNTs than for BCNNTs. Through the concerted substitution of B and N for C in the in situ grown CNTs, template growth of BCNNTs follows the CNTs growth without causing topological changes.
Moscow State University Activities on Research of Space Environment Effect on Materials
Authors: Novikov Lev S. 
Published: April 2011

ABSTRACTMain areas of Skobeltsyn Institute of Nuclear Physics Moscow State University activities in study of space environment effect on materials are following: effect of space radiation on spacecraft materials and equipment elements, spacecraft charging in space plasma in various orbits, influence of atomic oxygen flux on materials in LEO, surface erosion and destruction under impact of micrometeoroids and small particles of space debris.The methods of computer and laboratory modeling used are described. Results of the researches are presented, as far as some experiments onboard the MIR station and ISS are described. Principle problems for contemporary and future research are proposed for discussion. Principle problems for contemporary and future research are proposed for discussion.
Nanodosimetry: Present and perspectives
Authors: Chipara Mircea 
Published: April 2011

ABSTRACTThe reasons to develop a nanodosimetry theory are critically reviewed. The necessity of such an approach is proved. The main features of nanodosimetry are analyzed. The predicted enhanced sensitivity of nanomaterials to ionizing radiation is demonstrated. It is concluded that the lifetime of nanomaterials in the harsh conditions of the space environment has to be accurately estimated.
Multifunctional Single-Walled Carbon Nanotube Polycarbonate Composites
Authors: Chen Jian , Ramasubramaniam Rajagopal , Liu Haiying 
Published: April 2011

ABSTRACTUniform single-walled carbon nanotube (SWNT) polycarbonate composites were fabricated using noncovalently functionalized, soluble SWNTs. These composites showed dramatic improvements in the electrical conductivity and mechanical tensile strength at low SWNT loading. We also observed a stress-induced SWNT alignment in polycarbonate film, which is very difficult to achieve with pristine SWNTs.
Whisker Formation in Sn Coatings on Cu
Authors: Chason Eric , Reinbold Lucine , Kumar Sharvan 
Published: April 2011

ABSTRACTIn the microelectronics industry, Sn is often electroplated as a protective layer on Cu conductors. Pure Sn layers on Cu develop whiskers that can cause component failures and have even been implicated in the loss of several satellites. Alloying Sn with Pb suppresses whisker formation, but the push towards Pb-free processing will make this unacceptable in the future. To understand the driving forces and mechanisms of whisker formation on pure Sn, we are measuring the kinetics of stress evolution and intermetallic formation in Sn/Cu layers. By using thin films of Sn and Cu, we can monitor the stress evolution in real time using wafer-curvature based techniques. Preliminary results of stress evolution in vapor-deposited films are presented showing the evolution of tensile stress in the Cu layers and compressive stress in the Sn layers.
Nanocrystalline Soft Magnetic Alloys for Space Applications
Authors: Willard Matthew A. , Francavilla Thomas , Goswami Ramasis , Harris Vincent G. 
Published: April 2011

ABSTRACTThis study focuses on a Co-based nanocrystalline alloy (Co84.55Fe4.45Zr7B4) with potential for long-term high temperature use. As an indication of their performance, core losses were measured on toroidal samples using a Walker AC permeameter over a frequency range of 0.1 to 500 kHz, at induction amplitudes of 100, 300, and 500 mT, and temperatures from 22 to 300°C. For a given frequency and maximum induction amplitude, the losses were invariant as a function of measurement temperature. Vibrating sample magnetometry provided the magnetization and hysteretic losses as a function of temperature. As the temperature of the alloy was raised to 300°C from room temperature, the saturation magnetization (120 emu/g)was reduced by less than 15%. A toroid was aged at 300°C for up to 300 hours and core loss measured as a function of aging time at the previously mentioned frequencies and induction amplitudes. The losses were invariant over the aging time.
Investigation upon Mechanical Properties of Thin Film Silicon Under Cryogenic Temperature
Authors: Zhao Yi , Zhang Xin 
Published: April 2011

ABSTRACTThin film silicon material has an extensive application in cooling satellite instrumentation under cryogenic environment. The performance and reliability of the cooling system heavily depends on mechanical behavior of the thin films. In this paper, we built an experimental setup and used compressive gas to actuate a silicon thin film under both room temperature and cryogenic temperature. The elastic modulus was derived from the film's deflection using laser Michelson interferometer. Stress distribution was obtained using Micro Raman spectroscopy. It was found that Young's modulus derived from the deflection increases with decreasing temperature. Compressive stress concentrated at edge centers of the film and tensile stress occurred at the center. There is a good match between the theoretical predications and experimental observations.
Simulation of InAsSb/InGaAs Quantum Dots for Optical Device Applications
Authors: Allmen Paul von , Lee Seungwon , Oyafuso Fabiano 
Published: April 2011

ABSTRACTSelf-assembled InAsSb/InGaAs quantum dots are candidates for optical detectors and emitters in the 2–5 micron band with a wide range of applications for atmospheric chemistry studies. It is known that while the energy band gap of unstrained bulk InAs1−xSbx is smallest for x=0.62, the biaxial strain for bulk InAs1−xSbx grown on In0.53Ga0.47As shifts the energy gap to higher energies and the smallest band gap is reached for x=0.51. The aim of the present study is to examine how the electronic confinement in the quantum dots modifies these simple considerations. We have calculated the electronic structure of lens shaped InAs1−xSbx quantum dots with diameter 37 nm and height 4 nm embedded in a In0.53Ga0.47As matrix of thickness 7 nm and lattice matched to an InP buffer. The relaxed atomic positions were determined by minimizing the elastic energy obtained from a valence force field description of the inter-atomic interaction. The electronic structure was calculated with an empirical tight binding approach. For Sb concentrations larger than x=0.5, it is found that the InSb/ In0.53Ga0.47As heterostructure becomes type II leading to no electron confined in the dot. It is also found that the energy gap decreases with increasing Sb content in contradiction with previous experimental results. A possible explanation is a significant variation is quantum dot size with Sb content.
Correlation of Optical Luminescence with Radiation Hardness in Doped LiNbO3 Crystals
Authors: Thomes William J. , Simmons-Potter Kelly , Potter Barrett G. , Weichman Louis S. 
Published: April 2011

ABSTRACTTransient ionizing radiation fields have been observed to cause substantial optical loss in undoped LiNbO3 crystals operating at 1.06 microns. This loss is slow to recover and makes the selection of this material for Q-switch applications in radiation environments unfeasible. We have studied the effects of Mg doping on the radiation response of LiNbO3 crystals and have investigated the optical luminescence of doped and undoped samples. Our results indicate a strong correlation between crystal defects, formed primarily during crystal growth, and the radiation-induced optical loss exhibited by these materials. These findings have enabled us to produce radiation-hard LiNbO3 crystals for use in high gamma-field environments.
Low-Temperature Grain Boundary Diffusion Data Measured from Historical Artifacts
Authors: Kremer R.J. , Dayananda M.A. , King A.H. 
Published: April 2011

ABSTRACTDiffusion processes in typical metals are slow at room temperature but there are many applications for which very long-term use is envisaged and stability needs to be assured over a timescale of 10, 000 years, where even slow processes can be important. It is common to perform accelerated tests at higher temperatures and extrapolate the necessary information from the measurements so obtained. We have tested the validity of this type of extrapolation for room-temperature, grain boundary diffusion in the copper-silver system, by measuring low-temperature diffusion profiles in antique samples of Sheffield plate.
Electrochemical Techniques Applied to Metals Conservation
Authors: Costa Virginia 
Published: April 2011

ABSTRACTA review of the applications of electrochemical methods to the conservation of metal artifacts is presented with regards to their use in treatment and research. As treatment techniques electrochemical methods have been used for cleaning, stabilization and consolidation for many years. Presently electrochemical methods are increasingly being used as a research tool, allowing the identification and quantification of products present at the surface of the artifacts as well as evaluation of the compatibility between materials. Examples of application to silver-copper alloys and stainless steels are presented.
Atomic Oxygen Treatment and Its Effect on a Variety of Artist's Media
Authors: Miller Sharon K.R. , Banks Bruce A. , Waters Deborah L. 
Published: April 2011

ABSTRACTAtomic oxygen treatment has been investigated as an unconventional option for art restoration where conventional methods have not been effective. Exposure of surfaces to atomic oxygen was first performed to investigate the durability of materials in the low Earth orbit environment of space. The use of the ground based environmental simulation chambers, developed for atomic oxygen exposure testing, has been investigated in collaboration with conservators at a variety of institutions, as a method to clean the surfaces of works of art. The atomic oxygen treatment technique has been evaluated as a method to remove soot and char from the surface of oil paint (both varnished and unvarnished), watercolors, acrylic paint, and fabric as well as the removal of graffiti and other marks from surfaces which are too porous to lend themselves to conventional solvent removal techniques. This paper will discuss the treatment of these surfaces giving an example of each and a discussion of the treatment results.
Effects of Water Exposure on the Mechanical Properties of Early Artists' Acrylic Paints
Authors: Hagan Eric , Murray Alison 
Published: April 2011

ABSTRACTThe mechanical properties of early artist's acrylic paints were investigated under controlled aqueous additive leaching for the purpose of identifying changes caused by cleaning paintings with water. Strength and stiffness values were obtained using a tensiometer to collect stress-strain curves of paint films. The results were compared to those from similar experiments in which paint films were tested under various age, temperature, and relative humidity (RH) values. Strength and stiffness both increased with decreased temperature, decreased RH, increased age, and increased additive removal. The most significant impact on mechanical properties was caused by lowering temperature to the Tg region around 5°C. Dramatic changes in properties were caused by RH fluctuations; however, the magnitudes were negligible in comparison to those induced by low temperature. Removal of water-soluble additives produced a uniform increase in tensile strength and secant modulus at all RH values. The films were equally responsive to fluctuations in RH before and after additive leaching. In comparing the material properties across a wide range of conditions it is evident that the acrylic paints in this study were not significantly altered by the amount of water exposure involved in cleaning paintings.
The Changing Mechanical Properties of Aging Oil Paints
Authors: Mecklenburg Marion F. , Tumosa Charles S. , Erhardt David 
Published: April 2011

ABSTRACTThe stiffening and embrittlement of oil paints over time has been a real concern for those responsible for the long term care and preservation of paintings. This paper examines the effects of time, pigments, relative humidity (RH), temperature and solvents on the mechanical properties of traditional oil paints. In this way it is possible to determine the role of each factor in causing the paints to become brittle. Even after 14 years the oil paints show little evidence that the long term “maturing” processes have begun to slow down. It is shown that there seems to be little correlation between the time paint requires to “dry-to-the-touch” and the longer term mechanical properties. Both low and high temperature levels can increase the stiffness of the paints though the mechanisms are quite different. Considerable hydrolysis of the paints occurs early in their history and the ones that hydrolyze most quickly are the ones that remain the most flexible.