bluuebunny/crossref_metadata_2025 huggingface dataset:
Femtosecond fluorescence studies of Auramine O in hybrid sol-gel derived films
Authors: Prosposito P. , Quatela A. , Zhang H. , Glasbeek M.
Published: April 2011

Femtosecond fluorescence upconversion experiments have been performed on Auramine O (a diphenylmethane dye) in polymethylmethacrylate (PMMA) and in hybrid organic/inorganic solgel based films.

All the investigated samples showed a fast decay (few picoseconds) and a long decay (hundreds of picoseconds). The fast components are representative of the rapid cooling of the excess excitation energy to the matrices. The long components are representative of the excited-state lifetime of the probed molecules. Auramine O in solid matrices showed lifetimes longer than in liquid solutions. Torsional diffusion motions of the two phenyl rings of the molecule are held responsible for the excited-state dynamics.

A dynamic Stokes shift has been observed for all samples. The lack of a rise time when detection was on the red side is explained in terms of an adiabatic coupling between emissive and nonemissive excited states, as is the case of liquid solutions. Different spectral shifts in PMMA and hybrid glasses have been measured. A different coupling between the emissive and nonemissive excited states for the two types of matrices is considered.
Reliability Analysis of an Inorganic-Organic Hybrid Sol-gel Material System for Waveguiding Applications
Authors: O'Brien S. , Winfield R. J. , Connell A. , Crean G. M.
Published: April 2011

A novel epoxy-functionalised sol-gel material system for use in photonic waveguiding applications has been developed for use in short-range optical interconnect applications. The sol-gel material is deposited by spin coating to form a thin-film up to 25μm in thickness. The resulting film is selectively cross-linked using photo-lithography, as part of a UV-thermal curing process. A tunable film refractive index over the range 1.48–1.515 is demonstrated. The near-field images of transmitted radiation (633nm) from fabricated waveguide structures shows both waveguiding and efficient light confinement within the UV-thermally produced core regions. A thermal stability analysis of the waveguides following “Telcordia” environmental testing protocols for passive devices is presented. It is concluded that this materials system has the potential for use in waveguiding applications in environments where enhanced thermo-mechanical stability is required.
Preparation of Intercalative Organic/MoO3 Nanohybrid Thin Films and Their VOC Gas Sensing Properties
Authors: Matsubara Ichiro , Murayama Norimitsu , Shin Woosuck , Izu Noriya
Published: April 2011

Organic/MoO3 nanohybrid thin films have been successfully prepared by an ex-situ intercalation process. The host MoO3 films were first deposited on LaAlO3 (LAO) single crystal substrates by using a CVD method followed by the intercalation of butylammonium ions, (BuNH3)+, into the MoO3 films to give (BuNH3)xMoO3 thin films. The preparation of highly b-axis oriented MoO3 films is crucial to prepare the (BuNH3)xMoO3 films. The (BuNH3)xMoO3 thin films exhibit a resistance-increasing response to aldehyde gases as in the case of bulk samples, whereas no response was observed for methanol, ethanol, chloroform, acetone, toluene, and xylene. The thin film process developed for intercalative organic-inorganic hybrid makes it possible to apply this material in VOC sensor devices.
From Hybrid Films to Mesoorganized Multi-metal-oxide Nanocrystalline Films (M3NF), preparation and characterization.
Authors: Boissière Cédric , Grosso David , Smarsly Bernt , Brezesinski Torsten , Lepoutre Sophie , Nicole Lionel , Valle Marcos J. C. , Antonietti Marcus , Sanchez Clément
Published: April 2011

High quality and reproducible thin silica and non-silica mesoporous films were obtained with mono-oriented organised mesoporosity, fitting various symmetry groups (i.e. p6m, Pm3n, Im3m, …). The Evaporation Induced Self Assembly (EISA) mechanism of structuration was studied through in-situ time-resolved SAXS, interferometry and spectroscopic ellipsometry investigations during dip-coating. A Modulable Steady State (MSS) was found during which the system is in quasi-equilibrium with its environment and during which the final structure is formed. The corresponding Self-Assembly mechanism was found to be governed by a competition between evaporation, micellization and condensation that depend on various critical chemical and processing parameters the influence of which have been summarized into directly usable phase diagrams. Calcined SiO2 and TiO2 mesoporous films structure (pore size and anisotropy, porous volume and surface) and mechanical properties (young modulus) were investigated by UV-Visible spectroscopic ellipsometry. Finally, thanks to a specially designed block copolymer, one further step was accomplished by achieving the dip coating and controlled nano-crystallisation of various metallic and multi-metal-oxides films (M3NF) of composition CoxTi(1-x)O(2-x) with ilmenite or doped Anatase structure, and SrTiO3 and MgTa2O6 with perovskite structure. Attending the well known magnetic, dielectric and catalytic properties of these structures, M3NF are highly compatible with high technology applications in microelectronic, energy transfer devices, spintronic, nano-mechanical adjustments, data storage, oxide fuel cells …
Modification of Metal Alkoxide Precursors by Organofunctional Bidentate Ligands: Chemical Problems and Opportunities for Materials Syntheses
Authors: Schubert Ulrich , Bauer Ulrike , Fric Helmut , Puchberger Michael , Rupp Wolfgang , Torma Viktoria
Published: April 2011

Bidentate ligands are potentially useful to modify metal alkoxides precursors for sol-gel processing. However, anionic bidentate ligands are needed to get a strong coordination, while diamines as neutral bidentate ligand form coordination polymers [Ti2(OR)8(diamine)2]∞ when reacted with Ti(OR)4. The Lewis acidity of metal alkoxides may cause organic side reactions. The first is the formation of ester and water in the reaction with carboxylic acids, and therefore carboxylate-substituted metal oxide clusters of the general composition MnOx(OH/OR)y(OOCR)z are obtained instead of substituted monomeric precursors. The second side reaction discussed is the cleavage of β-diketones by metal alkoxides. Despite this side reaction, 3-acetyl-6-trimethoxy-silyl-hexane-2-one is a useful compound to prepare single-source precursos for silica/metal oxide composites.
Three Dimensional Structure and Liquid Transport Behavior of Siloxane Gels with Co-continuous Macropores
Authors: Saito Haruko , Nakanishi Kazuki , Hirao Kazuyuki , Jinnai Hiroshi , Morisato Kei , Minakuchi Hiroyoshi
Published: April 2011

The geometrical properties of co-continuous macroporous silica monoliths have been studied by laser scanning confocal microscopy (LSCM) and a comparison with mercury intrusion method has been made. From three-dimensional images obtained by LSCM observation, probability density distributions of curvatures have been calculated on gel skeleton surface by the “sectioning and fitting method”. Measured liquid transport behavior in macroporous siloxane gels has been related to the obtained curvature distributions.
Rational Design of Macrocellular TiO2 and V2O5 Monoliths Obtained Through Soft Chemistry and Air-liquid Foams
Authors: Carn F. , Steunou N. , Colin A. , Livage J. , Sanchez C. , Backov R.
Published: April 2011

Chemistry of shapes appears as a strong interdisciplinary field of research that encompasses both the area of soft matter, physical-chemistry and soft chemistry. In this general context, hierarchical inorganic macrocellular monoliths have been obtained using air-liquid foams as a macroscopic pattern while lyotropic mesophases are employed to create porosity at the mesoscale. At the macroscopic length scale, both cell sizes and shapes as well as the Plateau borders thickness and topologies can be designed with a strong degree of control. Some examples with different inorganic network as TiO2 and V2O5 are depicted with specific characterizations.
Pattern Formation on Silicon-on-Insulator
Authors: Flack Frank S. , Yang Bin , Huang Minghuang , Marcus Matt , Simmons Jason , Castellini Olivia M. , Eriksson Mark A. , Liu Feng , Lagally Max G.
Published: April 2011

The strain driven self-assembly of faceted Ge nanocrystals during epitaxy on Si(001) to form quantum dots (QDs) is by now well known. We have also recently provided an understanding of the thermodynamic driving force for directed assembly of QDs on bulk Si (extendable to other QD systems) based on local chemical potential and curvature of the surface. Silicon-on-insulator (SOI) produces unique new phenomena. The essential thermodynamic instability of the very thin crystalline layer (called the template layer) resting on an oxide can cause this layer, under appropriate conditions, to dewet, agglomerate, and self-organize into an array of Si nanocrystals. Using low-energy electron microscopy (LEEM), we observe this process and, with the help of first-principles total-energy calculations, we provide a quantitative understanding of this pattern formation. The Si nanocrystal pattern formation can be controlled by lithographic patterning of the SOI prior to the dewetting process. The resulting patterns of electrically isolated Si nanocrystals can in turn be used as a template for growth of nanostructures, such as carbon nanotubes (CNTs). Finally we show that this growth may be controlled by the flow dynamics of the feed gas across the substrate.
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

We 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.
Kinetics of Linear Defect Formation in Gallia-Doped Rutile.
Authors: Empie Nathan , Edwards Doreen
Published: April 2011

The diffusion of Ga2O3 into the surface of single crystal[001] rutile leads to the insertion of β-gallia subunits along {210} planes of the parent rutile structure. These linear defects introduce hexagonally shaped tunnels, approximately 2.5 å in diameter, normal to the]001] surface. Because these tunnels may serve as highly reactive sites for the attachment of macromolecules, we are exploring the application of these linear defects for creating nanostructures. The current work investigates the kinetics of defect formation and the factors that affect defect periodicity and orientation. Gallium oxide was applied to the surfaces of [001]-oriented TiO2 single-crystal substrates via a sol-gel spin-coating process using a gallium-containing precursor. Thermal treatments were systematically varied to obtain different defect surface structures. Defect orientation and the surface concentration of rows of defects were characterized via tapping mode atomic force microscopy.
Temperature and Flux dependence of ion induced ripple: a way to study defect and relaxation kinetics during ion bombardment
Authors: Chan Wai Lun
Published: April 2011

We have measured the temperature and ion flux dependence of the ripple wavelength on a Cu(001) surface during low energy ion sputtering. We analyze these results in terms of a linear instability model and identify different experimentally observed behavior with different mechanisms of relaxation and surface defect kinetics. In a high temperature regime, diffusing species on the surface are mainly thermally induced while in a lower temperature range, the diffusing species are ion beam induced. At even lower temperature, thermal diffusion is deactivated and the surface relaxes through an athermal mechanism. We define a transition between different defects formation kinetics in temperature and flux phase space and discuss how the defect kinetics model can be extended to different materials system.
On the Formation Kinetics of Thin Nanopatterned Layers on Silicon Wafers Created by Hydrogen Plasma Exposure
Authors: Job R. , Huang Y. L. , Ma Y. , Zölgert B. , Düngen W.
Published: April 2011

Czochralski silicon wafers which are treated by hydrogen plasma at ca. 260 °C are structured at the surface due to the high reactivity of atomic hydrogen. “Nanopatterned” (np) Si layers with average structure diameters below 100 nm are created. The thickness of the np-Si layer is on the order of 100 nm. The morphology of np-Si layers depend on the applied plasma power and the exposure time. The formation of np-Si layers is discussed in the frame of a combined etching/ redeposition mechanism. Annealing at T ≥ 800 °C causes a reconstruction of np-Si layers and the appearance of tensile stress in the wafers up to a depth of several micrometers.
Dynamic spatial ordering of thin film nanostructures by rapid spatio-temporal surface modulations
Authors: Zhang Wei , Zhang Chi , Kalyanaraman Ramki
Published: April 2011

We present novel results showing that the application of a rapid spatio-temporal surface modulation in-situ with film deposition directs the assembly of ordered nanostructures. Co nanoclusters of approximately 50 nm in size were assembled into one-dimensionally ordered arrays spaced 400 nm apart on Si (100) substrates during film growth of a 0.5 nm thick film. This ordered arrangement was achieved under e-beam evaporation of Co with simultaneous two-beam pulsed laser interference irradiation. The ordering length scale was consistent with the theoretical two-beam fringe spacing. For a thicker Co film, the particles were irregularly shaped, like that of a rapidly solidified liquid-like structure. From this evidence, the mechanism for ordering is partly attributed to thermal effects due to the spatially periodic laser interference heating of the cobalt nanoparticles. This dynamic in-situ process, without the need of any pre-or post-patterning of the substrate or film, is promising as an economical and simple approach to assemble ordered nanostructured films. The author can be reached via e-mail at ramkik@wuphys.wustl.edu
laser ablation of carbon films used for transfer of electronic device
Authors: Sameshima Toshiyuki , Andoh Nobuyuki
Published: April 2011

Pulsed laser-induced ablation using diamond-like carbon (DLC) films is reported. Pulsed XeCl excimer laser induced heating revealed that 200-nm DLC films formed by sputtering method had high heat resistivity and structural relaxation was induced by laser heating. SiO2 layers formed on the DLC films were successively removed from the DLC surface by laser heating at 350 mJ/cm2. C-O bond reaction probably occurred and stickiness of SiO2 to carbon was reduced. Laser induced forward transfer of Al/SiO2 was also demonstrated using DLC films with laser heating.
The Mechanical Properties of Thin Polymer Films from Nanoindentation
Authors: Jones F R , Hayes S A
Published: April 2011

The thermomechanical properties of thermoset polymeric materials are shown to be suitable for detecting relevant degradative processes in the matrix of a fibre composite. In space environments, the surface of the material will be modified first because of the diffusion of the active molecules. Nanoindentation has been shown to be capable of determining changes in viscoelastic properties of thin polymer films and at surfaces of bulk material. The Hysitron Triboscope has been used to characterise an epoxy resin and polycyanurate in dynamic and static scanning modes. Dynamic nanoindentation has been shown to provide a full description of the viscoelastic response. Progress has been made in analysing static indentation for time dependence.
Developing Glassy Magnets from simulated Composition of Moon/Mars Regolith for Exploration Applications
Authors: Ray C. S. , Ramachandran N. , Rogers J.
Published: April 2011

The feasibility of preparing glasses and developing glass-ceramic materials that display magnetic characteristics using the simulated compositions of Lunar and Martian regoliths have been demonstrated. The reported results are preliminary at this time, and are part of a larger ongoing research activity at the NASA Marshall Space Flight Center (MSFC) with an overall goal aimed at (i) developing glass, ceramic and glass-ceramic type materials from the Lunar and Martian soil compositions in their respective simulated atmospheric conditions, (ii) exploring the potential application areas of these materials through extensive materials characterization, and (iii) further improving the related materials properties through a variation of the processing methods. This research activity is an important component of NASA's current space exploration program, which encourages feasibility studies for materials development using in situ resources on planetary bodies to meet the technological and scientific needs of future human habitats on these extra terrestrial outposts. This paper presents an overview of this on-going work at NASA (MSFC) and reports on a few selected results obtained to date.
Vertically Aligned Carbon Nanotubes as the Sputter Resist in Space Propulsive Systems
Authors: Yap Yoke Khin , Kayastha Vijaya , Menda Jitendra , Vanga Lakshman Kumar , Wang Jiesheng , Kieckhafer Alex , Massey Dean , King Lyon B.
Published: April 2011

Two-types of vertically aligned multi-walled carbon nanotubes (VA-MWNTs) are evaluated as the protective coatings against ion erosion in electric propulsion systems. A series of experiments have been conducted to understand the erosion rate and erosion mechanism of these VA-MWNTs. These experiments were carried out with Xe propellant at an ion current density of 5 mA/cm2. We found that the erosion rates of both types of VA-MWNTs were changing with time. Such a nonlinear erosion process is explained according to a possible erosion mechanism.
Advanced life support for space exploration: Air revitalization using amine coated single wall carbon nanotubes.
Authors: Moloney Padraig , Huffman Chad , Gorelik Olga , Nikolaev Pasha , Arepalli Sivaram , Allada Ramakumar , Springer Micah , Yowell Leonard
Published: April 2011

The challenges posed by long duration human space flight have made regenerable air revitalization a critical technology. Current systems using disposable lithium hydroxide do not address the difficulties presented by long duration missions. Solid amine systems offer the capability to regeneratively adsorb CO2 using an amine—impregnated porous substrate. Desorption of CO2 is then achieved by exposing the system to vacuum or by increasing temperature. However, thermal inefficiencies and system size constraints prevent adoption of regenerable systems on current and future space vehicles. A key challenge is the thermal management of the adsorbing bed. The adsorbing surface increases in temperature which reduces adsorbing efficiency. The removal of CO2 reduces temperature, which in turn produces a loss in regeneration efficiency. These thermal inefficiencies necessitate prohibitively large volumes of traditional solid-amine materials, which do not have optimized surface areas and pore distributions. Single-wall carbon nanotubes (SWCNTs) may provide a means to increase surface area of the amine support and thermal efficiency. Recent work by Cinke et. al. provided a method of functionalizing SWCNTs and increasing the surface area to the order of 1500 m2/g [1]. We will report on the production of free standing, high surface area carbon nanotube structures currently being impregnated with amines. This novel SWCNT/amine approach will be compared with the current state of the art polymer structure-based system and characterized using SEM, TEM, surface area analysis through Brunauer-Emmett-Teller (BET), and also thermogravimetric equilibrium absorption. Results of SWCNT material improvements from processing modifications will also be presented.
Multifunctional Power-Generating and Energy-Storing Structural Composites for U.S. Army Applications
Authors: South Joseph T. , Carter Robert H. , Snyder James F. , Hilton Corydon D. , O'Brien Daniel J. , Wetzel Eric D.
Published: April 2011

Many U.S. Army systems, such as ground vehicles and fully equipped soldiers, are comprised of multiple subcomponents which each typically perform unique functions. Combining these functions into single, multifunctional components could reduce mass and improve overall system efficiency. In particular, creating structural materials that also provide power generating or energy storing capacity could provide significant weight savings over a range of platforms. In this study, structural composite batteries, fuel cells, and capacitors are proposed. To ensure performance benefits, these multifunctional composites are designed so that the materials involved in power and energy processes are also load bearing, rather than simply packaged within monofunctional structural materials. Fabrication and design details for these multifunctional systems, as well as structural and power/energy performance results, are reported. Critical material properties and fabrication considerations are highlighted, and important technical challenges are identified.
Screening Of The Thermal Endurance Of Spacecraft Materials By Kinetic Modelling
Authors: Moser M. , Heltzel S. , Semprimoschnig C. O. A. , Garcia Martin G.
Published: April 2011

Future science missions of the European Space Agency (ESA) to the inner part of the solar system will require the use of materials at an extreme radiation and temperature environment. A major concern regarding the selection of these materials is the thermal behaviour and the thermal stability. In this paper ways are shown to assess the thermal endurance of polymers by kinetic modelling. Two commonly used kinetic models, the one following the ASTM E 1641 and ASTM E 1877 standards and the other following the Model Free Kinetics (MFK) approach, are presented and compared to each other with the given example of two competing polyimide films, Kapton HN® of DuPont and Upilex S® of Ube Industries1, which were tested within ESA's critical materials technology program.
Advanced Carbon-based Material as Space Radiation Shields
Authors: Gupta Sanju , Patel Rishi J. , Smith Nathaniel D.
Published: April 2011

Carbon-based materials including microcrystalline diamond, nanocrystalline diamond, and carbon nanotubes films were prepared by microwave plasma-assisted chemical vapor deposition (MWCVD) technique. While the former were submitted to gamma radiation doses of 1, 5, and 20 Mrad, the latter to low energy electron beam of 30 keV or to 30 GeV/cm2) to study the radiation-induced structural transformation. The characterizations were performed prior to and after irradiation using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction, techniques. Microcrystalline diamond showed a dramatic modification in the structural properties only after a cumulative dose of 26 Mrad (2 Grad/cm2), while nanocrystalline carbon showed a relatively small but systematic transformation with increasing gamma radiation dose. The results indicate that nanocrystalline carbon tends to reach a state of saturation when submitted to 26 Mrad doses of gamma radiation, suggesting the possibility of fabricating radiation buffer materials that would undergo internal sp3 ⇔ sp2 inter-conversion while absorbing ionizing radiation without changing their average microstructure and protecting the device/material underneath. Single- and multi-walled nanotubes exhibited structural modifications after 5.5–8 hrs of continuous exposure to electron beam. The variation in the characteristic X-ray peaks for multi-walled and single-walled corresponding to intertube spacing and the high frequency Raman band around 1580 cm−1 (G band) are reflected in their corresponding spectra. The results indicate that there is an increase in the intertube spacing for multi-walled nanotubes due to electron irradiation. While single-wall nanotubes tends to ‘collapse’ after > 8 hours of exposure forming multi-wall nanotubes analyzed using scanning electron microscopy and Raman spectroscopy. These C materials can be employed for preventing space radiation from reaching sensitive materials and electronic devices at least for short term experiments and entitled them as ‘space radiation shields’.
Electron Beam Radiation of Carbon Nanotubes-Polymer Composites
Authors: Najafi Ebrahim , Lee Jong-Oh , Shin Kwanwoo
Published: April 2011

The degradation of PMMA-CNT thin film composites was examined, using electron beam radiation as a function of CNTs concentration. The findings show that the addition of CNT fillers can significantly reinforce composites against the irradiation induced degradation of PMMA, in which polymer free radicals are mainly responsible for the progress of the degradation. The results show that CNT networks are able to effectively disperse irradiated electrons through the matrix. The saturation of reinforcement effects was observed at a concentration of CNTs of approximately 0.5 wt%. This concentration was interpreted in terms of the critical concentration needed for percolation of the CNTs network, and this was further verified by sheet resistivity measurements. Free radical interactions with CNTs were also investigated by accelerated electron beam radiation and thermogravimetric analysis. CNTs were able to inhibit the free radical proliferation during a degradation process and to reduce the extent of degradation of the composites.
Radiation Effects and Defects in Cubic Boron Nitride. A Promising Multifunctional Material for Severe Environment Conditions.
Authors: Nistor S. V.
Published: April 2011

Cubic boron nitride (c-BN) is a synthetic material which exhibits exceptional physicochemical properties such as: hardness, thermal conductivity, thermo-chemical stability, semiconducting properties and radiations resistance. Such outstanding properties make it a promising multifunctional material for applications in extreme conditions, as those found in the outer space environment. Its further use for such applications requires, however, a much better understanding of the lattice defects and radiation damage properties. Here we present the results of multifrequency ESR studies concerning the native and radiation induced point defects in crystalline c-BN under irradiation with high intensity 1MeV electron beams.
Low Earth Orbital Atomic Oxygen Interactions with Spacecraft Materials
Authors: Banks Bruce A. , de Groh Kim K. , Miller Sharon K.
Published: April 2011

Atomic oxygen, formed in Earth's thermosphere, interacts readily with many materials on spacecraft flying in low Earth orbit (LEO). All hydrocarbon based polymers and graphite are easily oxidized upon the impact of ∼4.5 eV atomic oxygen as the spacecraft ram into the residual atmosphere. The resulting interactions can change the morphology and reduce the thickness of these materials. Directed atomic oxygen erosion will result in the development of textured surfaces on all materials with volatile oxidation products. Examples from space flight samples are provided. As a result of the erosive properties of atomic oxygen on polymers and composites, protective coatings have been developed and are used to increase the functional life of polymer films and composites that are exposed to the LEO environment. The atomic oxygen erosion yields for actual and predicted LEO exposure of numerous materials are presented. Results of in-space exposure of vacuum deposited aluminum protective coatings on polyimide Kapton indicate high rates of degradation are associated with aluminum coatings on both surfaces of the Kapton. Computational modeling predictions indicate that less trapping of the atomic oxygen occurs, with less resulting damage, if only the space-exposed surface is coated with vapor deposited aluminum rather than having both surfaces coated.
Materials Testing Activities within ESA in Support of Future Inner Solar System Missions
Authors: Semprimoschnig Christopher O. A. , Heltzel Stan , Eesbeek Marc van
Published: April 2011

In this paper the ESA internal approach regarding the assessment of materials for inner solar system missions is presented. A main part of the work is devoted to the assessment of thermal control materials and space environmental testing at elevated temperature. As these materials are the most exposed it is important to understand how they will interact with the relevant space environment at elevated temperature. Driving parameters for materials degradation are discussed and on-going testing efforts are described. An important input parameter for thermal models is the knowledge of the end of life values for the thermo-optical properties as these determine the equilibrium temperatures. In certain cases end of life testing needs to be done when the uncertainty of extrapolation is too high.
The Role of βFeOOH in the Corrosion of Archaeological Iron
Authors: Watkinson David , Lewis Mark R. T.
Published: April 2011

The chloride bearing corrosion product akaganéite (βFeOOH) can form during postexcavation corrosion of chloride infested archaeological iron and is able to corrode iron in contact with it. Its action on iron is examined using βFeOOH synthesized from ferrous chloride and iron powder. Using weight measurements the hygroscopicity of βFeOOH is established. The influence of relative humidity on the corrosion of iron powder mixed with βFeOOH is examined by dynamic mass change within a climatic chamber. At 20°C and 12% relative humidity, iron in contact with βFeOOH did not corrode. At 15% relative humidity slight iron corrosion was detected after 160 hours, but at 35% relative humidity corrosion occurred after a few hours. Surface adsorbed chloride was removed from βFeOOH by aqueous washing and this reduced its hygroscopicity. The reported metastability of βFeOOH was examined via XRD of a 23 year old sample, which was found to be still entirely composed of βFeOOH. These results provide better understanding of βFeOOH corrosion of iron, corrosion control of chloride infested iron using dry storage and the effect of aqueous washing on archaeological iron.
Linseed Oil Paint as Ionomer: Synthesis and Characterization
Authors: Tumosa Charles S. , Erhardt David , Mecklenburg Marion F. , Su Xingfang
Published: April 2011

As linseed oil ages, hydrolysis and oxidation produce acid groups on the polymer chain that may lead to ionomeric behavior. The effect of these changes is difficult to determine in old paints because of the lack of records of environmental and treatment histories that can alter the physical properties significantly. A series of paints were made that have chemical properties similar to those of aged paints and that mimic old paints. Their properties seem to show flexibility as well as coherency but low strength and a high susceptibility to solvents.
Analysis of Stucco Floors from the Citadel of the Archaeological Zone of Teotihuacan, Mexico
Authors: Montes Luis Torres , García Manuel Reyes , Gazzola Julie , Gómez Sergio
Published: April 2011

Severe decay of the stone façade of the Pyramid of Quetzalcoatl, one of the more remarkable structures in the World Heritage Site archaeological zone of Teotihuacan, Mexico, is caused by the presence of humidity and salt crystallization. The floors were analyzed to determine whether water and salts were filtering up from the ground and to find a way to reduce the penetration of water. Analyses of the lime plaster and organic matter were carried out by traditional wet chemical methods in order to discover the possible recipe that is the basis of the technology used by Pre-Columbian masons. The presence of an organic mucilage and fiber was identified. The organic components of the floors were analyzed using FTIR of extracts, while mucilage from leaves of a local cactus, Opuntia sp, that is used traditionally as a cementing material in plasters, was analyzed for comparative purposes to determine whether the mucilage was also used in pre-Columbian times. X-ray spectrometry and x- ray diffraction were also used to complement the study to identify the mineralogy of the plasters. This study shows that the Teotihuacanos used a composite material that has great durability, permitting the survival of the floors for almost 2000 years, but that also is succeptible to damage in a modern, stressed environment with high tourist traffic.
The Provenance of Ancient Glass through Compositional Analysis
Authors: Freestone Ian C.
Published: April 2011

Recent developments in the understanding of the low-magnesia soda-lime-silica or “natron” glasses of the first millennium A.D. are reviewed. It appears that glass production was divided between a small number of primary glass making centres, situated mainly in the Near East, and a large number of secondary fabrication workshops that remelted and shaped the lumps of raw, premelted glass. Glass may be related to its primary production group by elemental analysis and, where there are data from workshops, to the production centre or region. The recycling of old glass is revealed by trace element analysis, due to the contamination of primary glass compositions by small quantities of coloured glass incorporated in the recycled material. The analysis of isotopes of Sr and Pb allows the geological environment of the raw materials to be inferred and in some cases, provenance to be predicted.
RAMAN μ-SPECTROMETRY, A UNIQUE TOOL FOR ON-SITE ANALYSIS AND IDENTIFICATION OF ANCIENT CERAMICS AND GLASSES
Authors: Colomban Ph.
Published: April 2011

Raman micro-spectroscopy allows remote, non-destructive analysis of materials. Our laboratory was among the first to apply this technique to frescoes, oil and parchment painting. For five years we have focused our efforts on horn, ivory, tortoise shell and ancient ceramics and glasses. Crystalline and amorphous phases can be identified in both body and surface layer, including the glaze/glass-coloring nanosized pigments (e.g. in lustre ware, the first nano-optic device). Recent generation instruments are portable, which allows for on-site examination, for example, in a museum. In nanostructured, nanocrystalline/amorphous silicate glasses, glazes and most of their pigments, Raman parameters and their multivariable analysis are used to recognize compositions as well as to classify them as a function of their processing. This overview addresses the procedure, choice of the exciting radiation, control of the Raman resonance, data processing and extraction of relevant parameters such as the index of polymerization and different signatures that may be characteristic of specific glazes and pigments. Didactic examples are chosen among pottery that representative of the different production technologies used in the Roman, European (Medici, Meissen, Chantilly, Mennecy, Saint-Cloud, Sèvres), Islamic (Iznik, Kütahya, Safavid) and Asian (Vietnam) worlds.
Nanoparticles in Lustre Reconstructions
Authors: Fredrickx P. , Verbeeck J. , Schryvers D. , Hélary D. , Darque-Ceretti E.
Published: April 2011

It is increasingly apparent that the spatial distribution of Ag and Cu nanoparticles in lustre glazes is an important factor in determining the colour displayed by the decoration. Using STEM-EDX of cross sections, this distribution can easily be imaged, as is demonstrated in two modern reconstructions of lustre decorations from Granada, Spain. On the nanoscale, the difference in colour can be related to a different spatial distribution of the Ag and Cu particles, with the brownish gold variant consisting of a top layer of Ag nanoparticles with an underlying layer of Cu nanoparticles while in the yellowish golden lustre Cu specks are unevenly dispersed.
Understanding Glass Deterioration in Museum Collections through Raman Spectroscopy and SIMS analysis
Authors: Robinet Laurianne , Eremin Katherine , Fearn Sarah , Pulham Colin , Hall Christopher
Published: April 2011

The combination of Raman spectroscopy and Secondary Ion Mass Spectrometry can improve understanding of the chemistry of the glass alteration process. Formic and acetic acids play an important role in the alteration of museum glass objects placed in a humid atmosphere. Raman spectroscopy indicates that the soda-rich glass structure is modified differently when exposed to a humid versus a humid and polluted atmosphere at 60°C. Formic acid was not formed from soda-rich glass in the presence of carbon dioxide, high humidity and light.
Manipulation of Nickel Nanoparticles Deposited on HOPG
Authors: Atashbar Massood Z. , Bliznyuk Valery N. , Singamaneni Srikanth
Published: April 2011

Nickel nanowires were fabricated by electrodepositing Ni from an aqueous plating solution onto the step edges of Highly Oriented Pyrolytic Graphite (HOPG). Freshly cleaved HOPG was exposed to a plating solution of nickel and electro chemically deposited by cyclic voltametry. The morphology of the deposited nanoparticles was studied using an Atomic Force Microscope (AFM) in non-contact mode. The magnetic force of interaction between the nanoparticles was studied by magnetizing the particles. The critical force to displace the nanoparticles was estimated using contact mode of AFM.
Nanomagnetic Structures: Fabrication and Interactions
Authors: Sellmyer David J. , Sui Y. C. , Xu Y. F. , Yan M. L. , Sorge K. D. , Skomski R.
Published: April 2011

Magnetic nanostructures with desirable properties such as monodispersed size and crystallographic texturing can be fabricated by a number of synthetic techniques. In this paper, we discuss methods for creating nanoclusters with fine control of individual propertiesand their interactions, as well as a promising chemical technique that provides control of several properties simultaneously. Current and potential applications also will be addressed.
Room-temperature magnetoresistance of one-dimensional magnetite (Fe3O4) nanostructures
Authors: Liu Zuqin , Zhang Daihua , Zhou Chongwu
Published: April 2011

In this paper, we present our recent studies on the synthesis and magnetoresistance of single crystalline Fe3O4 core-shell nanowires and nanotubes. Homogeneous Fe3O4 nanowires/tubes with controllable length, diameter and wall thickness were synthesized. The as-prepared material composition and stoichoimetry have been carefully examined and confirmed with a variety of characterization techniques including XRD, EDS, XPS, and TEM. Magnetoresistance under different temperatures was systemically studied. Up to 1.2% room temperature magnetoresistance was observed in the as synthesized nanowires/tubes under a magnetic field of B = 1.8 T.
Stretchability of complex patterns of thin metal conductors on elastomeric skin
Authors: Lacour Stéphanie P. , Wagner Sigurd
Published: April 2011

We have previously shown that 25nm thick gold stripes on 1mm thick silicone membrane retain electrical conduction when stretched up to 100% along their long dimension. To function as electrical interconnects in conformable integrated circuits, the metallization must be stretchable in arbitrary directions. Therefore we have made and tested the mechanical and electrical properties of complex conductor patterns including X and Y oriented lines and cross junctions. We find that the metal patterns continue to conduct under uniaxial stretching in the X or Y direction and under radial, biaxial stretching.
Kinetic Control of Dome Cluster Composition by Varying Ge Deposition Rate
Authors: McDaniel E. P. , Drucker Jeff , Jiang Qian , Crozier P. A. , Smith David J.
Published: April 2011

The mean size of dome clusters grown by molecular beam epitaxy of pure Ge onto Si(100) at substrate temperatures, T, of 550°C and 650°C is deposition rate dependent. For samples with nominal Ge coverages near 8 ML (1 ML = 6.78 ×1014 atoms/cm2) and deposition rates between 1.4 and 17.5 ML/min, higher deposition rates decreased the mean dome diameter and increased the dome areal density. Additionally, the critical volume for the pyramid-to-dome transition decreases with increasing deposition rate for islands grown between T = 550°C and 650°C. By this measure, the Ge content of the dome clusters rises with increasing deposition rate. Quantitative, nm-resolved electron energy loss spectroscopy (EELS) measurements taken in a scanning transmission electron microscope confirm these results. For domes grown at T = 650°C with rates of 1.4 ML/min and 17.5 ML/min, EELS indicates 59% and 70% Ge compositions, respectively. These results show that dome cluster composition may be kinetically controlled by varying the Ge deposition rate.
Morphological Changes while Growing Nickel Monosilicide Nanowires
Authors: Kim Joondong , Anderson Wayne A. , Guliants Elena A. , Bunker Christopher E.
Published: April 2011

Nickel monosilicide (NiSi) nanowires (NWs) have been fabricated in a DC magnetron system by the Metal Induced Growth (MIG) method. The NW growing stages were sequentially observed by scanning electron microscopy. Deposited Ni on SiO2 coated Si wafers has been first grooved and agglomerated by thermal heating at 575 °C. In the sputtering procedure, Ni as a catalyst reacted with sputtered Si forming clusters. Nanowires were grown in the same directions on each cluster. Raman spectroscopy and Energy Dispersive Spectroscopy indicated the NW composition as NiSi. The linear propagating property of NWs was used to form self-assembled nanobridges (NBs) in trenched Si wafers. The affinity of NWs can be used on various substrate materials with less thermal damage. NiSi composed MIG-NBs are promising candidates as nanoscale contacts due to the features of low resistivity and low temperature processing giving less potential damage on fabricated structures.
Molecular Dynamics Study of Grain Growth in Nanocrystalline Materials in the Presence of Dopants
Authors: Millett Paul C. , Panneer Selvam R. , Saxena Ashok
Published: April 2011

Molecular dynamics simulations of bulk nanocrystalline Cu with dopant atoms segregated in the grain boundary regions were performed to investigate the impediment of grain growth during annealing at constant temperature of 800K. In this parametric study, the concentration and atomic radii mismatch between the dopants and the host atoms were systematically varied to determine how to most effectively retard grain growth. It is found that samples with positive excess enthalpy (ΔH) underwent various degrees of grain growth; however, when ?H was negative, no coarsening occurred. Also, ΔH varied linearly with dopant concentration with the slope equal to the enthalpy of segregation, in agreement with previous theoretical work.
Trapping of Hydrogen in Carbon Nitride Films During or After High Temperature Heat Treatment
Authors: Ingram David C. , Kayani Asghar , Lanter William C. , DeJoseph Charles A.
Published: April 2011

Thin films of carbon nitride deposited by ion beam assisted deposition or by magnetron sputter deposition typically contain a significant fraction of hydrogen, 1–30 atomic percent (at.%). In order to improve the thermal stability of the properties of the films, attempts have been made to minimize the hydrogen trapped during deposition. Such films typically have less than 5 at.% hydrogen. On heating these films in ultra high purity (99.999%) argon, it has been found that above 600°C they start to absorb significant amounts of hydrogen, this despite retaining their mechanical integrity. The composition of the films is determined using Rutherford Backscattering Spectroscopy in combination with Elastic Recoil Spectroscopy for detecting the hydrogen isotopes. In this paper, the possible sources of the hydrogen have been investigated by exposing the samples to deuterated water or deuterium gas during or immediately after the heat treatment.
Influence of Macro- and Nanotopography, Thin Film Thermomechanical Behavior and Process Parameters on the Stability of Thermocompression Bonding.
Authors: Stamoulis Konstantinos , Mark Spearing S.
Published: April 2011

The quality of wafer-level, gold thermocompression bonds is critically dependent on the interaction between the wafer topography, the thin film properties, the process parameters and tooling used to achieve the bonds. This study presents mechanics modeling of the effect of wafer topography. An analytical expression for the strain energy release rate associated with the elastic deformation required to overcome wafer bow is developed. Furthermore, a simple contact yielding criterion is used to examine the pressure and temperature conditions required to flatten nano-scale asperities in order to achieve bonding over the full apparent area. The analytical results combined with experimental data for the interface bond toughness obtained from four-point bend testing indicate that the overall wafer shape is a negligible contributor to bond quality. A micro-scale bond characterization based on microscopic observations and AFM measurements show that the bond yield is increased with increasing bond pressure.
Thermal Processing of Polycrystalline NiTi Shape Memory Alloys
Authors: Frick Carl P. , Ortega Alicia M. , Tyber Jeff , Gall Ken , Maier Hans J. , El.M. A. , Liu Yinong
Published: April 2011

The objective of this study is to examine the effect of heat treatment on polycrystalline Ti-50.9 at.%Ni subsequent to hot-rolling. In particular we examine microstructure, transformation temperatures and mechanical behavior of deformation processed NiTi. The results constitute a fundamental understanding of the effect of heat treatment on thermal/stress induced martensite, which is critical for optimizing mechanical properties. The high temperature of the hot-rolling process caused recrystallization, recovery, and hindered precipitate formation, essentially solutionizing the NiTi. Subsequent heat treatments were carried out at various temperatures for 1.5 hours. Transmission Electron Microscopy (TEM) observations revealed that Ti3Ni4 precipitates progressively increased in size and changed their interface with the matrix from being coherent to incoherent with increasing heat treatment temperature. Accompanying the changes in precipitate size and interface coherency, transformation temperatures were observed to systematically shift, leading to the occurrence of the R-phase and multiple-stage transformations. Room temperature stress-strain tests illustrated a variety of mechanical responses for the various heat treatments, from pseudoelasticity to shape memory. The changes in stress-strain behavior are interpreted in terms of shifts in the primary martensite transformation temperatures, rather then the occurrence of the R-phase transformation. The results confirm that Ti3Ni4 precipitates can be used to elicit a desired isothermal stress-strain behavior in polycrystalline NiTi.
on the relationship between the electric double layer and actuation in ionomeric polymer transducers
Authors: Akle Barbar J. , Leo Donald J.
Published: April 2011

Ionic polymer transducers are soft actuators that perform large bending deflections when voltages on the order of 1–5 V are applied across their thickness. Previous work showed that actuation performance of ionic polymer transducers is strongly correlated with the capacitance due to surface charge accumulation. Increasing the capacitance of the actuator increases the motion of the charges and increases the strain produced under the application of an electric field. Ionomeric transducers consist of an ionomer, such as Nafion (a product of DuPont), sandwiched between two high surface area electrodes. An electric double layer is formed on the interface between the cathode and the adsorbed positive ions. A novel plating technique which was previously developed is used to vary the morphology of the polymer-electrode interface to investigate the parameters of importance to the formation of the electric double layer. Electromechanical transducer tests are performed as a function of electrode morphology to correlate surface charge accumulation with the deflection generated by the transducer.