bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineralization of water-in-oil emulsion droplets
Authors: Fornasieri Giulia , Badaire Stéphane , Backov Rénal Vasco , Poulin Philippe , Zakri Cécile , Mondain-Monval Olivier
Published: April 2011

Using reverse emulsion systems, we were able to trigger mineralization confined at an oil-water interface. In this process, the alcoxide silica precursor is dissolved in the oil continuous phase of the emulsion and diffuses through the bulk to the interface where it starts to hydrolyze and condense as soon as a certain concentration threshold is attained. The process takes place only in the presence of a water soluble surfactant inside the droplet. This surfactant leads to the presence of a controlled mesoporosity inside the silica shells. The obtained objects could be used in different encapsulation applications.
Sol-Gel Silica Particles for Controlled Release Applications
Authors: Barbé Christophe , Calleja Sandrine , Kong Linggen , Drabarek Elizabeth , Bush Alexandra , Sizgek Erden , Finnie Kim
Published: April 2011

Using sol-gel technology combined with water-in-oil (W/O) emulsions, we have developed an innovative method for producing ceramic particles with independent control over the release rate and particle size. The average particle size can be varied from 10 nm to 100 μm and is controlled by the emulsion chemistry. The release rate can be independently varied from mg/hours to mg/month, and is controlled by the internal microstructure of the particles and the initial sol-gel chemistry.
Surface-modified Zirconium Oxide Clusters and their Use as Components for Inorganic-Organic Hybrid Materials
Authors: Gao Yu , Dragan Denise Silvia , Jupa Myhedin , Kogler Franz René , Puchberger Michael , Schubert Ulrich
Published: April 2011

Pre-formed transition metal oxide clusters with methacrylate ligands were polymerized in the presence of organic co-monomers to form inorganic-organic hybrid polymers. The number of polymerizable ligands and thus the crosslinking density of the hybrid polymers can be varied for a given cluster type by partially exchanging the methacrylate ligands for non-reactive ones. The properties of the hybrid polymers can also be varied by adjusting the conditions of the polymerization reaction, especially by a pre-polymerization procedure. It is shown that the thermal stability of polystyrene crosslinked by Zr6O4(OH)4(OMc)12 is thus greatly improved.
Synthesis and Characterization of Imide-Oligosiloxanes Hybrid Nanocompisite (Imide HYBRIMER) by Reaction of Nano Amine Modified Oligosiloxane and Dianhydride
Authors: Lee Tae-Ho , Kim Jeong Hwan , Ko Ji Hoon , Bae Byeong-Soo
Published: April 2011

Imide-oligosiloxanes hybrid nanocomposites (Imide HYBRIMER) were synthesized and their unique structure and thermal and mechanical properties were investigated. Imide HYBRIMER was made by reaction with nano-sized amine oligosiloxane (AO) and dianhydride, where oligosiloxane moieties were cross-linked by imide bonds to form three-dimensional nanocomposite. The AO were prepared from condensation reaction with aminopropyltirmethoxysilane (APTS) and diphenylsilanediol (DPSD) under base catalysts without water and solvents. The preparation of imide HYBRIMER was completed through the thermal imidization of amic acids, which were formed by reaction with amines groups in the AO and two different kinds of dianhydrides. The imide HYBRIMER were stable up to 400°C and thermal expansion coefficients measured by thermo-mechanical analysis (TMA) were varied from 33 to 80 ppm/°C. Higher thermal stabilities and mechanical strengths could be obtained by incorporating siloxane moieties in hybrid nanocomposites. The imide HYBRIMER, which has three dimensional network, could induce very low birefringence about 0.003, which was lower than that of linear typed polyimides.
Iron Oxide – Doped Mesostructured Silica Films
Authors: Supplit Ralf , Hüsing Nicola , Fritscher Christina , Jakubiak Patrycja , Kessler Vadim G. , Seisenbaeva Gulaim A. , Bernstorff Sigrid
Published: April 2011

Poly(ethylene oxide)—poly(propylene oxide)—poly(ethylene oxide) (PEO-PPO-PEO) was reacted with iron ethoxide in a molar ratio of 1:2. This modified surfactant was used as a template for the synthesis of mesostructured, nanocomposite iron oxide-silica films and powders. Grazing incidence (GI)-SAXS measurements of the films showed that depending on the concentration of the surfactant wormhole-like, 2d-centered rectangular, orthorhombic and lamellar nanocomposite structures were formed. Interestingly, the mesoscopic ordering of the orthorhombic and 2d-centered rectangular pore structure is retained even after calcination at 1000 °C for one hour. The influence of heat treatment on the mesostructure was investigated by GI-SAXS, TEM and N2-sorption measurements.
LDH-DNA Nanohybrids: a complete biophysical characterization
Authors: Leroux Fabrice , Belkacen Málha Ben , Guyot Ghislain , Taviot-Guého Christine , Léone Philippe , Cario Laurent , Desigaux Léa , Pitard Bruno
Published: April 2011

Recently, LDH have been considered as a new kind of gene delivery system [1, 2]. In this work, we report the formation of magnesium-gallium LDH-DNA nanohybrids using the coprecipitation method. This “self assembly” approach enabled the incorporation of long DNA fragments up to 6000–8000 bp. X-ray diffraction analyses indicate a parallel orientation of DNA double helix in the interlamellar space with respect to the hydroxide sheets. The Mg/Ga molar ratio within the hydroxide layers appears to be determined by DNA macromolecules which may interact with charged complexes that form during cation hydrolysis. The presence of DNA macromolecules also inhibits the crystal growth: hydrodynamic diameter measurements revealed homogeneous populations of particles with a mean diameter ranging from 90 to 150 nm, compatible with cell penetration through endocytosis. Concerning the charge surface of this new DNA delivery system, ζ-potential measurements indicate negative values ranging from –20 to - 40 mV which suggest incomplete DNA intercalation. Yet, this small negative surface might be suitable for protecting DNA from extra-cellular degradations without preventing cell penetration.
Layered Tungsten Oxide-Based Hybrid Materials Incorporating Transition Metal Ions
Authors: Ingham Bridget , Chong S. V. , Tallon Jeff L.
Published: April 2011

Layered organic-inorganic hybrid materials based on tungsten oxide as the inorganic framework have been synthesised to include transition metal ions. The resulting materials have been characterised using a number of techniques. X-ray diffraction shows an interlayer expansion with increasing alkyl length. Infrared vibrational spectra of manganese tungstate compounds indicate the organic amine molecules are neutrally charged, and the inorganic framework is unaltered as one varies the organic intercalate. The magnetic behaviour of the materials has also been explored using a SQUID magnetometer. In the manganese tungstate hybrids an antiferromagnetic (AF) transition is observed, which decreases in temperature as the inorganic interlayer spacing is increased. A nickel tungstate hybrid sample, on the other hand, displays a ferromagnetic transition, which we attribute to a canted AF phase below 15 K. In all cases studied, the behaviour can be mapped to an effective moment (Peff) per transition metal ion, which agrees well with theoretical and literature values for other transition metal oxides.
Intercalation of n-alkylamines in the vapor phase into vanadium pentoxide xerogel dispersed into silica matrix
Authors: Figueiredo Mariza A. , Oliveira Herenilton P.
Published: April 2011

In this work, we report a new intercalation reaction: three different n-alkylamines (n-butylamine, n-hexylamine and n-octylamine), in vapor phase, were intercalated into non-dispersed vanadium pentoxide xerogel and into this lamellar material homogeneously dispersed in Si–O–Si network (obtained by polycondensation of the silicon alkoxide) interpenetrated with V–O–V and V–OH–V polymeric chains. The reaction with non-dispersed xerogel leads to increase of interlamelar distance for low time of reaction (up to 2 hours) and after 24 hours we observed a new phase. In contrast, for the reaction with xerogel dispersed in silica, it was observed only the increase of the basal distance retaining the original bi-dimensional structure (00l diffractions lines were observed); suggesting that the silica matrix stabilizes the vanadium pentoxide structure as the result of a mutual “solubility” due to cross-linking and entanglement of both components. In addition, for this reaction it was observed a selective amine intercalation. The reactions were monitored using powder X-ray diffraction, Fourier-transform infrared and electronic spectroscopy, electron paramagnetic resonance and scanning electron microscopy.
Control of the Morphology of the Layered-Silicate Epoxy Nanocomposite
Authors: Chen Chenggang , Tolle Tia Benson
Published: April 2011

Polymer layered-silicate nanocomposites have attracted great attention due to their unique nanostructure and properties. The property of the nanocomposite is determined by the morphology of the nanocomposite. The typical morphologies of the nanocomposite are the intercalated and exfoliated nanostructures. In this study, the layered-silicate epoxy nanocomposite with different morphology can be controlled and achieved. The different morphology could include the intercalated nanostructure with the 15 Å increase of the interplanar spacing, the intercalated one with ∼150 Å increase of the gallery and fully exfoliated nanostructure.
The Structure of a Molybdenum Disulfide Intercalation Compound
Authors: Brüning Ralf , Bulmer Kristopher , Bissessur Rabin , Haines Robert I. , Varma Pravin , Emeneau Stephen
Published: April 2011

The X-ray powder diffraction spectrum of MoS2 with intercalated 5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane-1-acetic acid shows well-defined peaks as well as broad scattering. The X-ray scattering of this compound was simulated by generating model particles and calculating their X-ray scattering by evaluating the Debye sum. The match between the measured and simulated spectra was improved by trial-and-error. Matching the peak widths shows that the particles contain a total of about 6600 MoS2 units in about eight layers. The layers are oriented in the same direction (not turbostratic). However, they are translated randomly in the plane perpendicular to the stacking direction. In contrast to prior work on intercalation compounds, which considered various types of periodic reconstruction within the MoS2 layer, we obtain the best match with a non-periodic reconstruction in addition to a periodic superlattice. It involves dimer and trimer groupings of the molybdenum atoms with a random choice of centers. The intercalated tetraazamacrocycles form a two-dimensional glass. The effects of the key model assumptions on the calculated spectrum are demonstrated.
Effects of Surface Modification of Mg(OH)2 with Polysiloxane Oil and Silica Additive on the Flame Retardancy and Mechanical Properties of LDPE-Mg(OH)2 Composites
Authors: Kodama K. , Hyodo T. , Shimizu Y. , Egashira M.
Published: April 2011

Composites of low density polyethylene (LDPE) and 40 wt% Mg(OH)2 modified with several kinds of polysiloxane oils were prepared in order to evaluate the effect of the surface modification of Mg(OH)2 on the mechanical properties and oxygen index of the composites. A composite containing Mg(OH)2 modified with methylhydrogen polysiloxane oil showed an oxygen index of 23.8% O2 and an elongation of 425%. These values were superior to other composites containing Mg(OH)2 modified with other kinds of polysiloxane oils. The oxygen index could be enhanced up to 24.8% by co-addition of 5 wt% fumed silica as another flame retardant to the composite of LDPE and 35 wt% Mg(OH)2 (modified with methylhydrogen polysiloxane oil), while fixing the total amount of the flame retardants at 40 wt%.
Responsive Polymer/Clay Aerogel Composites
Authors: Bandi Suneel , Schiraldi David A.
Published: April 2011

Clay aerogels are a relatively unexplored form of matter that are only now being investigated for use in the reinforcement of organic polymers. We have recently demonstrated an efficient process for producing these aerogels; we now report our preliminary work describing the preparation and properties of polymer/clay aerogel composites, including temperature-responsive materials.
Protein-Drug Interaction in the Nanocomposites Prepared by UV and IR Pulsed Laser Deposition
Authors: Sagawa J. , Nagare S. , Senna M.
Published: April 2011

Protein (bovine serum albumin; BSA)-drug (indomethacin; IM) nanocomposites were prepared by pulsed laser deposition (PLD) at two wavelengths, infrared (1064nm) and ultraviolet (266nm), from uniformly dispersed mixture of BSA and IM as a target. Composite particulates under 50nm were obtained with the coexistence of larger agglomerates over 200nm. Primary structure of BSA is preserved after laser irradiation by both wavelengths. Effects of electronic and vibrational excitation by UV and IR laser respectively on the secondary structure of the nanocomposites were examined by Fourier transform infrared spectroscopy (FT-IR). Chemical shift towards lower wavenumber and a broadening of the amide I band due to PLD treatment were observed by FT-IR. From curve fitting of the amide I into five components, we found the decrease in the ratio of α-helical / β-sheet components with increasing the laser fluence. The secondary structure of BSA is more sensitive to the laser fluence than the wavelength.
Heteroepitaxial Self-Assembly of Higher-Complexity Structures By Combining Growth Control with Nanopatterning
Authors: Floro Jerrold A. , Gray Jennifer L. , Atha Surajit , Singh Nitin , Elzey Dana , Hull Robert
Published: April 2011

We provide an overview of a novel self-assembly process that occurrs during GeSi/Si(001) strain-layer heteroepitaxy under conditions of limited adatom mobility. Suppression of copious surface diffusion leads to limited three-dimensional roughening in the form of pits that partially consume a thick, metastable wetting layer. The material ejected from the pits accumulates alongside, eventually forming a symmetric quantum dot molecule consisting of four islands bound to a {105}-faceted pit. These structures, which are of interest in nanologic applications, appear to arise from an intrinsic strain-relief mechanism in a relatively narrow regime of deposition conditions. An additional degree of morphological control is obtained by annealing films containing pits, before they evolve to full quantum dot molecules. Annealing promotes a one-dimensional growth instability leading to the formation of highly anisotropic grooves, bounded by long, wire-like islands. Finally, we show that patterns created in the Si substrate using a focused ion beam can control the location of quantum dot molecules, which is an additional critical step towards being able to use these structures for computing.
Dot Pattern Formation on Silicon Surfaces by Low-Energy Ion Beam Erosion
Authors: Ziberi B. , Frost F. , Höche T. , Rauschenbach B.
Published: April 2011

Experimental studies of low-energy (≤ 2000 eV) Ar+ ion beam erosion of Si surfaces under normal and oblique ion incidence with simultaneous sample rotation at room temperature show a variety of topographies. At oblique ion incidence, between 70° and 80° with respect to surface normal, dot patterns evolve (dot size ∼ 30 nm) with a remarkably high degree of ordering comparable to dot nanostructures reported for different III/V compound semiconductors. The mean size and ordering of these nanostructures can be adjusted by various process parameters like ion beam energy and erosion time, respectively. Scanning force microscopy (AFM) has been used to characterize the evolution of the surface topography.
Fabrication and Atomistic Modeling of Ion-Etch Nanostructures on Substrates
Authors: Stepanova Maria , Dew Steven K.
Published: April 2011

We have implemented and investigated numerically a new process to fabricate self-organized metal networks and lines on non-metallic substrates. We have deposited a thin film of Cu on silicon and glass substrates and etched the film by a 1 keV-energy Ar beam. Due to the kinetic mechanism known as sputter instability, nanosize metal patterns self-organize on the substrate at the stage when the etched surface reaches the metal/substrate interface. By numerical simulations, we have investigated the mechanism and control factors for the process.
Leakage Currents through Thin Silicon Oxide Grown on Atomically Flat Silicon Surfaces
Authors: Ignatescu Valerian , Blakely Jack M.
Published: April 2011

Atomically flat surfaces can be obtained by high-temperature annealing in UHV of specially patterned silicon samples. Thin silicon oxide layers were grown by dry oxidation on three types of surfaces: (a) atomically flat surfaces, (b) normal (stepped) surfaces cleaned in UHV by the same high-temperature annealing and (c) normal wafer surfaces, which underwent just an RCA chemical cleaning before oxidation. Atomic force microscopy (AFM) was performed to reveal the topography of the surfaces. Aluminum pads were deposited on these oxidized surfaces using photolithography techniques. The leakage current through the oxide was measured for all three cases. Our results show that the smoother the surface before oxidation, the smaller the leakage current.
Physical Self-Assembly And Nano-Patterning
Authors: Lu T.-M. , Ye D.-X. , Karabacak T. , Wang G.-C.
Published: April 2011

It is known that oblique angle deposition (or glancing angle deposition) can create 3D architectures that are otherwise difficult to produce using the conventional lithographic techniques. The technique relies on a self-assembly mechanism originated from a physical shadowing effect during deposition. In this paper we show examples of 3D nanostructures obtained by this oblique angle deposition on a templated substrate with regularly spaced pillar seeds. We show that common to this technique is the phenomenon of side-way growth on the seeds. The side-way growth leads to a fan-like structure at the initial stages of growth if the incident oblique angle is fixed during growth. Simulations based on a steering effect due to the attractive force between the incoming atom and the existing atoms on the surface produce a fanlike structure similar to that observed experimentally. We show that a two-phase substrate rotation scheme during deposition can dramatically reduce this fan-out effect and can lead to uniform and isolated columns.
Large Scale Engineered Nanostructured Surfaces by Reactive Ion Etching with Kinetically Self-Assembled Non-continuous Metal Film as Etching Mask
Authors: Wei Wei , Bachman Mark , Li Guann-Pyng
Published: April 2011

In this study, we explored the possibility of using annealed non-continuous metal film enabled etching technique to produce large nano-structured surfaces. Non-continuous Ag film is deposited on silicon wafer with a thin layer of silicon dioxide using E-beam deposition, and then vacuum thermal annealing was applied on the deposited films, causing nano-scaled Ag particles to migrate and agglomerate into self-assembled islands of larger nanometer dimensions. We controlled the density and average size of the metal islands through thickness of the initial film and subsequent annealing rates. Reactive ion etching through the metal islands mask into the underneath silicon dioxide layer was performed following the annealing process. Preliminary hydrophobicity experiments were carried out using the engineered nano-structured surfaces.
The Condition of the Materials Returned by the Genesis Mission
Authors: McNamara Karen M.
Published: April 2011

The Genesis mission returned to Earth on September 8, 2004 after a nearly flawless three-year mission to collect solar matter. The intent was to deploy a drogue chute and parafoil high over the Utah desert and to catch the fragile payload capsule in mid-air by helicopter. Unfortunately, both chutes failed to deploy, causing the capsule to fall to the desert floor at a speed of nearly 200 MPH. Still, Genesis represents a milestone in the US space program, comprising the first sample return since the Apollo Missions as well as the first return of materials exposed to the space environment outside of low Earth orbit and beyond the Earth's magnetosphere for an extended period. We have no other comparable materials in all of our collections on Earth.
Thermal Deicing of Polymer Composite Helicopter Blades
Authors: Dutta Piyush K. , Ryerson Charles C. , Pergantis Charles
Published: April 2011

This paper presents the results of an investigation to determine if thermal deicing methods (hot air, hot water, hot glycol, or radiative heat) would damage the composite materials in helicopter blades. Samples made from Blackhawk helicopter blades were thermally cycled in the regime of the temperatures of thermal deicing methods and then mechanically load tested. The strength reduction was compared with the number of thermal cycling and the temperatures of thermal cycling. The strength results and the modes of failure indicate that damages indeed do develop in the composites, especially along the bond line of the composite skin and the nomex core of the blade structure, and mechanical strength is reduced.
Syntactic Closed-cell Foams Based on Silicon Carbide
Authors: Ozcivici Engin , Singh Raman P.
Published: April 2011

Closed cell foams were fabricated by incorporating two different grades of hollow alumino-silicate spheres (cenospheres) into a silicon carbide matrix. The silicon carbide matrix was formed by the pyrolysis of a preceramic polymer, and multiple polymer infiltration and pyrolysis (PIP) cycles were employed to minimize the open voids in the material. The physical, mechanical and thermal properties of the fabricated foams were characterized as functions of the number of reinfiltration cycles. The open- and closed-void volume fractions were determined by measurements of bulk and skeletal densities. Mechanical properties, including strength and modulus, were evaluated using four-point bend and compression tests. Finally, thermophysical (thermal conductivity) values of the material were determined using laser-flash technique. This processing technique results in closed-cell syntactic foams with low density (≤ 1.8g/cm3), reasonable mechanical strength (∼ 30 MPa) and very low thermal conductivity (≤ 1 W/m-K). In this manner, this process can be used for the low-cost and net-shape fabrication of closed-cell silicon carbide syntactic foams for high temperature applications.
Investigation of the phase state of transformation shear bands in superelastic Ni-rich NiTi shape memory alloys with synchrotron diffraction
Authors: Schmahl W. W. , Baruj A. , Khalil-Allafi J. , Nebel H.
Published: April 2011

The deformation of superelastic NiTi due to the stress-induced transition from cubic B2 to monoclinic B19′ phase is localised in a Lüders-band-like transformation shear bands (TSB). We investigate the phase state and texture in the bands in-situ using diffraction with high-energy synchrotron-radiation. Residual austenite is observed to persist up to the end of the superelastic plateau in the stress-strain curve. The deformation corresponds to a displacement of the boundary of the TSB. After a certain volume of the specimen has transformed when the boundary has passed by, there is no further change of the crystallographic state of this volume up to the end of the macroscopic stress-strain plateau. The variant orientation texture is different at the surface from that present in the bulk.
Simulation of Absorbed Dose Distribution In Space Materials
Authors: Briskman Boris A.
Published: April 2011

The problems of absorbed dose distribution simulation at on-ground space material tests are discussed. Several approaches to such simulation, oriented to increase the test adequacy and economy, are analyzed. Sometimes, it is possible to use quantitative criteria of absorbed dose distribution depending on the specific space vehicle orbit. The assessment of reliable simulation of the radiation spectrum may be made, for example, by introducing a special numerical characteristic of the depth dose profile in a material - depth dose criterion. For this purpose, it is recommended to use the ratio of the exponent index of the depth dose profile (μ) to the density of the material (ρ). In the simplest form, the depth dose profile can be represented as a sum of two exponents. The first depth dose profile applies to a near-the-surface layer of 5 to 10 μm in thickness, and the second to a layer of from 10 μm up to, as a minimum, 100 μm in thickness. The reference values of μ/ρ for typical spectra of ionizing radiation are calculated.
Total Dose Radiation Effects In Si Nanocrystal Non-Volatile Memory Transistors
Authors: Petkov Mihail P. , Douglas Bell L. , Walters Robert J. , Atwater Harry A.
Published: April 2011

We report results pertinent to the high total dose tolerance of Si nanocrystal non-volatile memory cells. The nc-Si FETs made by ion implantation retained virtually unchanged write / erase characteristics, typical for the two-state devices, to cumulative doses exceeding 15 Mrad(Si).
Electron Spin Resonance Studies on Electron Beam Irradiated Carbon Nanotubes Dispersed in Styrene-Isoprene-Styrene Block Copolymer
Authors: Chipara Mircea , Beezhold Wendland , Webb Timothy , Zaleski Jeffrey M. , Stephenson Kristina , Dye David , Lau Kin-Tak
Published: April 2011

Electron spin resonance investigations on the effect of electron bombardment of nanocomposites obtained by dispersing carbon nanotubes within styrene-isoprene-styrene are reported. The experimental results revealed the absence of radiation-induced free radicals and a negligible effect of electron beam irradiation on the electron spin resonance spectra of carbon nanotubes.
FIB-Based Fatigue Testing of Silicon Nitride Thin Films for Space Applications
Authors: Chuang Wen-Hsien , Fettig Rainer K. , Ghodssi Reza
Published: April 2011

A novel micro-scale electrostatic actuator has been designed and fabricated to study fatigue properties of low-stress LPCVD silicon nitride thin films, which are the structural materials of microshutter arrays to be used in NASA's James Webb Space Telescope (JWST). To obtain different stress levels without high applied voltages, the electrostatic actuator was designed based on a resonant technique to achieve mechanical amplification. All fabricated devices were tested inside a focused-ion-beam (FIB) system with pressure of 10-6 torr at room temperature (23 ± 1 °C) and with the test duration ranging from 5 seconds to 8.5 hours, 105 to 109 cycles, respectively. From the experiment, no fatigue failure of low-stress LPCVD silicon nitride thin films has been observed up to 109 testing cycles, four orders of magnitude higher than the expected lifetime of the microshutter arrays. The presented test device and experimental technique can be extended to characterize fatigue properties for other thin film materials.
Beam Properties of the new Radiation Effects Research Stations at Indiana University Cyclotron Facility
Authors: von Przewoski B. , Rinckel T. , Manwaring W. , Ellis T. , Foster C. C. , Hall E. R. , Kinser T. , Murray K. M.
Published: April 2011

We describe two new beamlines for radiation effects research at the Indiana University Cyclotron Facility. Protons with energies up to 205 MeV are available. One of the beamlines offers momentum selected beams at energies as low as 52 MeV.
Highly Stable Polymers based on Poly(m -carboranyl-siloxane) Elastomers
Authors: Swain Anthony.C. , Patel Mogon , Murphy Julian.J.
Published: April 2011

Poly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methyl(phenyl)-silyl units were synthesised using the Ferric Chloride catalysed condensation reaction between di-chloro-di-organosilane and 1, 7-bis(di-methyl(methoxy)silyl)-m-carborane. These prepared polymers were aged either by heating in air at elevated temperature or by λ-irradiation from a 60Co source. Multinuclear (1H, 13C and 11B) solid and solution state nuclear magnetic resonance was used to evaluate degradation. λ-irradiation doses to 1 MGy were found to induce only a small reduction in elastomer properties as evidenced by a reduction in segmental chain dynamics. Ageing at temperatures below 350°C similarly displayed a small reduction in segmental chain dynamics together and a concomitant weight loss as measured by differential scanning calorimetry. Above 350°C degradation of the elastomer was dramatic with a decreased segmental chain dynamics and oxidation of the carborane cage, vide infra.
Piezoelectric PVDF Materials Performance and Operation Limits in Space Environments
Authors: Celina Mathew C. , Dargaville Tim R. , Chaplya Pavel M. , Clough Roger L.
Published: April 2011

Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest for large aperture space-based telescopes. Dimensional adjustments of adaptive polymer films are achieved via charge deposition and require a detailed understanding of the piezoelectric material responses which are expected to suffer due to strong vacuum UV, λ-, X-ray, energetic particles and atomic oxygen under low earth orbit exposure conditions. The degradation of PVDF and its copolymers under various stress environments has been investigated. Initial radiation aging studies using λ- and e-beam irradiation have shown complex material changes with significant crosslinking, lowered melting and Curie points (where observable), effects on crystallinity, but little influence on overall piezoelectric properties. Surprisingly, complex aging processes have also been observed in elevated temperature environments with annealing phenomena and cyclic stresses resulting in thermal depoling of domains. Overall materials performance appears to be governed by a combination of chemical and physical degradation processes. Molecular changes are primarily induced via radiative damage, and physical damage from temperature and AO exposure is evident as depoling and surface erosion. Major differences between individual copolymers have been observed providing feedback on material selection strategies.
Au Ion Induced Modification of C60 Thin Film Samples
Authors: Bajwa Navdeep , Ingale Alka , Avasthi D. K. , Kumar Ravi , Tripathi A. , Dharamvir K. , Jindal V. K. , Schmitt Michael , Kiefer W.
Published: April 2011

The present work reports phase transformations of thin films of C60 irradiated with 100 MeV 197Au8+ ions. This work is in continuation with our earlier work using 58Ni10+ and 16O6+ ions, to study the modification in C60 thin films. The study of C60 thin films using 197Au8+ ions, provides us enough additional data to investigate thoroughly the role of Se in causing phase transformations under different ion fluences. The Raman spectra indicate that swift heavy ion (SHI) irradiation results in several transformations of crystalline C60. At low fluences along with the fragmentation of C60 there is dimer/polymer formation. As fluence increases the dimer/polymer content first rises, optimizes, decreases and finally vanishes at very high fluences. At high fluences, all the C60 molecules as well as the polymer C60 break up, possibly resulting in nano-crystalline graphite embedded in amorphous carbon (a-C).
Confocal X-ray Fluorescence (XRF) Microscopy: A New Technique for the Nondestructive Compositional Depth Profiling of Paintings
Authors: Woll Arthur R. , Bilderback Donald H. , Gruner Sol , Gao Ning , Huang Rong , Bisulca Christina , Mass Jennifer
Published: April 2011

A confocal x-ray fluorescence microscope was built at the Cornell High Energy Synchrotron Source (CHESS) to determine the composition of buried paint layers that range from 10–80 μm thick in paintings. The microscope consists of a borosilicate monocapillary optic to focus the incident beam and a borosilicate polycapillary lens to collect the fluorescent x-rays. The overlap of the two focal regions is several tens of microns in extent, and defines the active, or confocal, volume of the microscope. The capabilities of the technique were tested using acrylic paint films with distinct layers brushed onto glass slides and a twentieth century oil painting on canvas. The position and thickness of individual layers were extracted from their fluorescence profiles by fitting to a simple, semi-empirical model.
Solid-State NMR and Resonance Raman Studies of Ultramarine Pigments
Authors: Federico Eleonora Del , Schoefberger Wolfgang , Kumar Rajeev , Ling Wen , Kapetanaki Sofia M. , Schelvis Johannes , Jerschow Alexej
Published: April 2011

We report on a study of ultramarine pigments via Colorimetry, resonance Raman, and 27Al, 29Si solid-state NMR spectroscopy. NMR parameters are shown to correlate well with the intensities of Raman signals corresponding to the chromophores S3−. and S2−.. Further, a correlation is established between the colorimetric parameters L* (lightness) and C* (chromaticity) and the paramagnetic shift in NMR spectra for both 27Al and 29Si. The parameter h (hue) appeared not to vary over the range of paramagnetic host concentrations studied. Preliminary results on faded pigments in both acidic and basic media show that the concentration of diamagnetic guest molecules in the sodalite lattice rises, and some of the paramagnetic species are replaced.
Protection Efficacy of Fluorinated Acrylic Copolymers Applied on Historical Italian Marbles.
Authors: Poli Tommaso , Toniolo Lucia
Published: April 2011

Use of polymeric materials to protect stone started in the 1960’s but the study and knowledge of the complex and multiple interactions between stone and polymers has been carried out only recently. In a previous paper [1] the problems related to the efficacy of a stone treatment (film formation, deep penetration and coating behavior) has been addressed. In this paper performance after a thermal and a simulated solar UV ageing has been evaluated. In particular the issues related to stability and durability of two fluorinated acrylic copolymers applied on two different Italian marbles, Carrara and S. Giuliano, have been investigated. The specimens characterized and treated with two new partially fluorinated acrylic copolymers, 2, 2, 2-trifluoroethyl methacrylate / methyl acrylate (TFEMA / MA) and trifluoromethyl-2, 2, 2-trifluorethyl methacrylate / methyl acrylate (HFIMA / MA), have been artificially aged in two different ways: with a long simulated solar UV ageing of 1000h and a thermal one at the same temperature (about 50°C) usually reached in the UV chamber, in order to separate the two ageing contributions (photochemical and thermal). After the ageing most of the testing methodologies suggested by UNI-Normal Italian protocol for evaluation of stone protective coatings, including capillary water absorption, static contact angles and colour variation, have been carried out. Slightly better protective efficacy was found for the HFIMA/MA before and after the two ageing. The important contribution of the thermal component in the worsening of the shielding efficacy has been assessed.
The role of Microstructure, Nanostructure and Composition in the Brilliant Red Slip of Roman Terra Sigillata Pottery from Southern Gaul
Authors: Sciau Philippe , Relaix Sabrina , Kihn Yolande , Roucau Christian
Published: April 2011

Terra sigillata ceramic is a fine ware produced during the Roman period. Its great success was due to its remarkable gloss, also called slip, which provides a bright deep red aspect. TEM-EELS and XRD techniques were used to understand the sub-microscopic origins of this singular aspect. Analysis investigations on five samples of two important Gaul workshops are described here. It appears that those samples have the same slip structure: sub-microscopic hematite and corundum crystals in a glass matrix. The matrix does not contain metallic ions, hematite is substituted in Al and Ti while corundum is substituted in Fe. The two crystal populations are homogeneously dispersed in the matrix and, together, give the specific red-orange colour to the sigillata.
The Analysis of Glazed Quartzite Sculpture from Kerma, Capital of Ancient Kush (Sudan)
Authors: Ellis Lisa , Newman Richard
Published: April 2011

Scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDS) was used to characterize the composition of glazes found on a collection of blue glazed, white quartzite sculptures, excavated from 1913–1916 by the Harvard University–Boston Museum of Fine Arts Expedition at the site of Kerma, the capital of ancient Kush, in today's Sudan. The scientific analysis of these artifacts shows the experimental nature of this extremely rare manufacture which appears to have developed out of faience technology.
Fabrication of FePt/M (M=C, Ag) Nanoparticulate Thin Films with Perpendicular Anisotropy
Authors: Huang Y. H. , Wan J. , Zhang Y. , Hadjipanayis G. C. , Weller D.
Published: April 2011

Magnetic nanoparticles with perpendicular anisotropy are attractive for applications in high-density recording media. For these applications, it is highly desirable to have particles with a size below 8 nm, a uniform size distribution, and a reduced ordering temperature to avoid unwanted particle agglomeration upon the required heat treatment to obtain the high anisotropy ordered L10 structure. In this work, FePt nanoparticles embedded in non-magnetic matrices M (M=C, Ag) have been fabricated by sputtering FePt and M multilayered thin films onto single crystal MgO [100] substrates at elevated temperatures up to 650 °C. The transformation from the disordered fcc to the ordered L10 phase in FePt nanoparticles was observed at temperatures as low as 300 °C. Besides the reduced transformation temperature, the deposited material showed an improved [001] texture for FePt/Ag thin films as compared to FePt/C due to lattice parameter matching between Ag and FePt. As the deposition temperature increases, the degree of atomic ordering approaches that of the fully ordered phase as indicated by the shift in the [002] XRD peak. TEM images showed that isolated particles with smaller average particle size (around 7 nm) were formed when the thickness of sputtered film is less than 4 nm. However, with a further increase of thickness of sputtered FePt film, a continuous layer of FePt particles was observed and the coercivity decreased rapidly due to a domain wall motion mechanism.
Nanowire Arrays with Specialized Geometries for Magnetoelectronics (Invited)
Authors: Stadler Bethanie J. H. , Kim Na hyoung , Tan Liwen , Zou Jia , Kelchner Kate , Cobianc Ryan K
Published: April 2011

This work focuses on the fabrication of magnetic nanowires with specialized geometries, such as Y-junctions, tapers and multilayers, for magnetoresistive sensor arrays. First, anodic alumina nanopores were grown with diameters of 20–250nm and lengths up to tens of microns. These pores were removed from their Al substrates and the barrier oxide was removed. Co nanowires were initially grown inside the pores by electrochemical deposition. It was shown that the coercivity and remnant magnetization could be tripled in (100)-oriented Co by shrinking the pore diameter/interpore spacing from 150/300nm to 40/80nm. These properties were further enhanced by fabricating (002)-oriented Co using the proper pH and applying a magnetic field during growth. The ability to connect two or more nanostructures is critical to the long term success of nanoelectronics and circuits. Here, Y-junctions were grown by subsequent growth of 40nm then 20nm pores such that two smaller pores extended from the bottom of each larger pore. These pores were then filled with Co in order to produce Y-junctions in the magnetic nanowires. Next, multilayered nanowires were fabricated with alternating layers of Cu and Co. The Co layer thickness was varied in order to study the affect of shape anisotropy on the magnetic properties of Co layers inside arrays. Finally, several configurations for magnetoresistive magnetic field sensors were described.
In-situ TEM Studies of Nanoscale Cu Interconnects Under Thermal Stress
Authors: An Jin Ho , Ferreira P.J.
Published: April 2011

Thermal fatigue during processing of microelectronic devices is a general reliability issue of concern in the microelectronic industry. In particular, as devices continue to be downscaled, the relaxation mechanisms operating under thermal stresses are expected to change. In this study, the microstructure of 1.8 micron and 180 nm wide Cu interconnects was identified through Transmission Electron Microscopy (TEM) imaging. In addition, In-situ TEM heating, performed in both type of specimens, is used to observe the differences in dislocation dynamics under thermal stress. In-situ TEM observations show delamination and inhibited dislocation motion in 180nm Cu lines, whereas in 1.8 micron Cu lines, grain boundaries seemed to act as dislocation sources. These different deformation mechanisms are expected to have an impact on the thermal fatigue behavior of Cu interconnects as the scale of devices is brought below 100 nm.
Suppression of Dewetting in Pulsed Laser Melting of Thin Metallic Films on SiO2
Authors: Eric Kline J. , Leonard John P.
Published: April 2011

Pulsed excimer laser projection irradiation has been successfully applied to completely melt and resolidify encapsulated elemental metal films of Au, Cu, Cr, and Ni directly on amorphous SiO2 substrates. A combination of narrow irradiated lines and appropriate SiO2 capping layers was used to obtain films that do not dewet when fully melted. Detailed processing maps were generated for Au and Ni, while equivalent trends for Cu and Cr were also noted. These systems were analyzed for common behaviors, and from these the principle factors, a basic process map is proposed to describe adequately these four systems. Experimental parameters and sample preparation criteria are presented to realize such resolidification studies in other metal systems.
Self-assembled Patterns in A Polymer Thin Film
Authors: Salac David , Lu Wei
Published: April 2011

This paper reports an experimental work using an electric field to induce morphological patterns in a thin polymer film. The film was spin-coated onto a glass wafer, and subsequently heated to above its glass transition temperature to allow viscous flow. An electric field was applied by two parallel electrodes spacing 10 mm apart. The initially flat polymer/air interface evolves into islands. The self-assembled islands exhibited a narrow size distribution and demonstrated spatial ordering. We attribute the pattern formation to the minimization of combined interface energy and electrostatic energy.
Energetics and Kinetics of Epitaxial Island Formation on Lattice Mismatched Patterned Substrates
Authors: Machtay Noah D. , Kukta Robert V.
Published: April 2011

Spontaneous self-assembly of nanostructures has been a problem of long-standing interest for fabricating advanced electrical and optical devices. One approach towards controlled self-assembly is epitaxial growth on topographically patterned substrates, where surface features act as preferred sites for island formation. The substrate shape addressed here is a periodic array of rectangular mesas. Strained-layer growth on such substrates has been observed to form as islands on the edge, in the center, or at a combination of those locations on the top of the mesa. The purpose of this investigation is to discern whether these morphologies are driven by energetic or kinetic mechanisms. An energetic analysis is done under the assumption that the system free energy consists of surface free energy and strain energy. Strain arises due to a lattice mismatch between the film and substrate materials. The film and substrate are treated as two-dimensional linearly elastic solids with similar elastic properties. Under the constraint of fixed volume, various island arrangements and shapes are compared to determine low energy configurations. Islands are assumed to have the shape of a circular arc, and island positions at the center of the mesa and on the mesa edges are considered for one, two, and three island systems. For symmetric configurations, depending on mismatch strain, surface energy, volume, and relative substrate dimensions, it is found that either the configuration with a single centered island or the configuration with two edge mounted islands may be favored. Allowing for asymmetry, a single island placed on one edge of the substrate mesa is generally the low energy configuration. This occurs because islands located near the edge of a raised mesa are most efficient at relaxing mismatch strain due to an increased compliance. Kinetic simulations of morphological evolution during combined deposition and surface diffusion are also conducted in order to identify possible metastable or slowly evolving non-equilibrium states.
Thermomechanical behavior and microstructural evolution in tantalum thin films
Authors: Knepper Robert , Jackson Katherine , Stevens Blake , Baker Shefford P.
Published: April 2011

Ta films were prepared in the metastable β phase using an ultra-high vacuum sputter deposition system. The stresses that arose during thermal cycles to 750°C were measured using an in situ substrate curvature measurement system, allowing oxygen content in the films to be minimized. A phase transformation from β to the stable α phase takes place in conjunction with distinct “jumps” in stress in the tensile direction during heating at approximately 400°C and 650°C. X-ray and electron backscatter diffraction (EBSD) analyses were used to determine grain sizes, along with crystal phase and orientation information. These results indicate a significant amount of grain growth accompanying the phase transformation. It is found that the measured total stress change is in reasonable agreement with that predicted by the combination of grain growth, crystal densification associated with the phase transformation, and stress relaxation.
Thin Films Stress Aging Study using Micromachined Cantilevers
Authors: Malhaire Christophe , Andrei Alexandru , Brida Sebastiano , Barbier Daniel
Published: April 2011

The purpose of the present work was to study the long term stress stability of thin films used in harsh environment sensors. A stress determination method, based on cantilevers curvatures measurements, checked by means of 3D finite element simulations, has been proposed. Stress measurements for dielectric (silicon oxide and nitride) and metallic (AlTi and TiW) thin films have been periodically performed at room temperature, after standard annealing (450°C / 30 min in a N2+H2 atmosphere) and after 4 weeks thermal aging at 150°C or 200°C.
Stability of WC Nanoparticles for NOx Reduction
Authors: Rumaiz A.K. , Shah S.I. , Lin H.Y. , Baldytchev I. , Chen J.G.
Published: April 2011

WC nanoparticles where synthesized using various Physical Vapor Deposition (PVD) methods such as reactive sputtering and Pulsed Laser Deposition (PLD). In both the methods the metal flux obtained is condensed in the presence of He gas. The structural properties of the samples where investigated using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). The feasibility of using nano-WC as an alternative catalyst for Pt is determined. A comparative study on two sample of WC, as-prepared and carburized W, was done. The samples were used to check for the reduction of NOx in a simple reactor. The carburized W shows activity at temperatures around 400°C whereas the as-prepared WC shows activity towards NOx reduction at a slightly higher temperature. The stability of both the sample was studied by performing the same experiment at a fixed temperature for an extended period of time. XPS and XRD confirm the formation of oxide phase after de-NOx experiments.