bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoplastic matrix composites for SPACE SOLAR POWER TRUSS (SSP)
Authors: Zhang Hao , Guidanean Koorosh , Nutt Steven
Published: April 2011

Thermoplastic matrix composites with a low glass transition temperature (Tg) have been developed for the Space Solar Power Truss (SSP). In this application, the truss is folded and packaged for launch, then expanded and deployed in space using a heat source. The present paper describes a resin film infusion process (RFI) used to fabricate laboratory-scale laminate tubes consisting of polyurethane and plain weave carbon fabrics. Subscale (1:5) sample tubes were formed to approximate the real tubes. The performance of the folded and unfolded tubes was measured under compression loading and compared with as-fabricated tubes at 25 and -75°C. Results show that elastic modulus was restored and even increased after bending. Stitched samples were also examined to evaluate the potential for reducing delamination at folds.
Preparation and Characterization of Electrospun Poly(ethylene oxide) (PEO) Nanofibers-reinforced Epoxy Matrix Composites
Authors: Lee Jae-Rock , Park Soo-Jin , Seo Min-Kang , Park Joung-Man
Published: April 2011

In this work, electrospinning was carried out using 12 wt.% poly(ethylene oxide) (PEO) solution under fixed tip-to-collect distance (10 cm) and voltage (15 kV) in order to fabricate nanofibers-reinforced composites. The content of PEO nanofibers was varied from 0 to 10 wt.% in the epoxy (EP) matrix resins. And the PEO powders-impregnated composites were also prepared to compare with physicochemecal properties of nanofibers-reinforced composites. Thermal and mechanical interfacial properties of EP/PEO nanocomposites were characterized by thermogravimetric analysis (TGA) and fracture toughness test, respectively. As a result, the PEO-based nanofibers-reinforced composites showed an improvement of thermal stability parameters (initial decomposed temperature (IDT) and integral procedural decomposition temperature (IPDT)) and fracture toughness factors (KIC and GIC), compared to the composites impregnated with PEO powders. And the thermal and mechanical interfacial properties of the composites were increased with increasing the PEO content, which could be probably attributed to the higher specific surface area and larger aspect ratio of PEO nanofibers, resulting in improving the demand performance of the nanocomposites.
Non-equilibrium Ti-Fe bulk alloys with ultra-high strength and enhanced ductility
Authors: Louzguine-Luzgin Dmitri V. , Louzguina-Luzgina Larissa V. , Kato Hidemi , Inoue Akihisa
Published: April 2011

The high-strength and ductile hypo-, hyper- and eutectic Ti-Fe alloys were formed in the shape of the arc-melted ingots with the dimensions of about 25–40 mm in diameter and 10–15 mm in height. The structure of the samples consists of cubic Pm 3 m TiFe and BCC Im 3 m β-Ti supersaturated solid solution phase. The arc-melted hypereutectic Ti65Fe35 alloy has a dispersed structure consisting of the primary TiFe phase and submicron-size eutectic structure. This alloy exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated β-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The reasons for the high ductility of the hypereutectic alloy are discussed.
Multifunctional Metal/Polymer Hybrid Fiber for Space and Aerospace Applications
Authors: Lee Jar-Wha , Hart Dale L. , Shinn Elizabeth T. , Cooley Abigail J. , White Edward L. , MacDowell Paul W. , Schomburg Erik , Slenski George A. , Watkins Anthony N. , Yang Robert L.
Published: April 2011

The stringent weight and space requirements of advanced space and aerospace systems have lead to a need for stronger, lighter, smaller, and more flexible cable and wiring components. Syscom has fabricated a multifunctional metal/polymer hybrid fiber from a rigid-rod type of polymer, such as poly(p-phenylene benzobisoxazole) (PBO) fiber, for signal transfer and electromagnetic interference (EMI) shielding in wiring and cable applications. The test results indicated that the metal/polymer hybrid PBO fiber exhibited ∼67% the electrical conductivity, ∼73% the weight and ∼200% the tensile strength of a comparable size of beryllium-copper CS95 wire. Additional experimental results of electric current carrying capability, cable shielding performance and atomic oxygen erosion protection will also be discussed.
Materials for High-Energy Radiation Shielding on Extra-Terrestrial Surfaces
Authors: Kiefer R. L. , Chapman J. L. , Boone A. R. , Thibeault S. A.
Published: April 2011

Polyethylene and polypropylene were used with simulated lunar regolith to make microcomposites as possible materials for habitat construction on extra-terrestrial surfaces. The polymer powders were used in various mass percents and thoroughly mixed with regolith powder before heating. A heated press or a microwave oven was used to heat the polymer/regolith mixture and form the micro-composite. The resulting materials were characterized by thermal analysis.
Proton Beam Induced Modifications in Multi-Functional Polyethylene-Based Carbon Nanotubes Composites
Authors: Pulikkathara Merlyn. X. , Pena-Paras Laura , McIntosh Daneesh , Chipara Mircea , Wilkins Richard , Barrera Enrique V. , Dye David , Zaleski Jeffrey M.
Published: April 2011

The space applications of composites obtained by dispersing carbon nanotubes within high-density polyethylene are analyzed. Electron spin resonance investigations on proton-irradiated composites are reported. The effect of ionizing radiation of the parameters of electron spin resonance spectra is studied. A radiation-induced increase of the concentration of uncoupled electronic spins delocalized over the conducting domains of carbon nanotubes is reported. It is concluded that radiation-induced modifications in such composites are weak.
Ground-Based Space Radiation Effects Studies on Single-Walled Carbon Nanotube Materials
Authors: Wilkins R. , Pulikkathara M. X. , Khabashesku Valery N. , Barrera E. V. , Vaidyanathan Ranji K. , Thibeault S. A.
Published: April 2011

Materials based on carbon nanotubes hold great promise for a variety of applications relevant to space exploration and the aerospace industry. Materials used for these applications will be subject to hostile environments including increased levels of high-energy particulate radiation. The type, energy range and fluence of the radiation will depend on the environment of the space mission. While it is not feasible to conduct an exhaustive study of the effects of space radiation on the earth's surface, ground-based experiments can be designed to simulate expected radiation environments using sources representing components of the relevant radiation environments. In this paper we present a compilation of results on materials based on singlewalled carbon nanotubes (SWNT) emphasizing nano-composites with raw (non-functionalized) and with 2–5% functionalized SWNTs in a polyethylene matrix. Materials such as these are promising candidates for multi-functional materials with good structural and radiation shielding characteristics. The radiation sources discussed here are relevant to the upper atmosphere (high energy neutrons), low earth orbit (medium energy protons) and interplanetary space (high energy protons and heavy ions). The samples are characterized before and after radiation with Raman spectroscopy which gives information on the structure of the SWNT and state of sidewall functionalization. Based on results from the SWNT papers (“buckypapers”) and the composites made from functionalized and non-functionalized SWNT, our data indicates that structural integrity and any sidewall functionalization of the SWNT in the nano-composite are radiation tolerant to radiation fluences commensurate with expected exposures on long-term spaceflight. More importantly, we find that the chemistry and material science of the processes used to produce the pristine and functionalized SWNT can affect the radiation characteristics of the nano-composites.
Investigation of Resiliency of Carbon Nanotubes and Gallium Nitride Nanocircuits to Simulated Space Radiation
Authors: Jacobs B. W. , Ayres V. M. , Crimp M. A. , Ronningen R. M. , Zeller A. F. , Shaw H. C. , Benavides J. B. , Kogut A. J. , Halpern J. M. , Petkov M. P.
Published: April 2011

Heavy ion irradiations of single and multi walled carbon nanotubes and total ionization dose of gallium nitride nanowires were investigated. Post irradiation analyses of samples were performed with transmission and scanning electron microscopy, atomic force microscopy and micro Raman spectroscopy.
Conducting and Antistatic Composites for Space Applications
Authors: Chipara Mircea , Sankar Jagannathan , Notinger Petre , Panaitescu Denis , Hui David , Aldica Gheorghe V. , Chipara Magdalena D. , Lau Kin-tak
Published: April 2011

The percolative dependence of the DC conductivity on the volume concentration of fillers for composites obtained by dispersing conducting particles into polymeric matrices is studied in detail. An empirical Boltzmann like dependence is proposed for the modeling of the dependence of DC conductivity versus filler concentration. This expression allows for a more accurate determination of the percolation threshold in the case of broad percolations. It is shown that the loading of the polymeric matrices with conducting fillers produces percolative-like changes of various physical properties (such as the reciprocal of the tensile strength and the reciprocal of the double integral of the resonance spectrum). Experimental mechanical, electrical, and electron spin resonance data on polyvinylchloride-carbon, polyvinylchloride-polyaniline, and polyethylene-polyaniline composites are reported.
Preventive Surface Treatment of Silicone Materials for Outgassing and Contamination Reduction in Space Application
Authors: Iskanderova Z. , Kleiman J. , Ng R. , Gudimenko Y. , Kaute D. A.
Published: April 2011

Contaminating films on spacecraft sensitive materials surfaces in many cases consist primarily of products resulting from the interaction of atomic oxygen with silicones. Necessity of a drastic reduction of the outgassing of volatiles and the following contamination has thus become a challenging problem. The effective surface conversion of space related organosilicone materials to oxide-based protective sub-surface layers under ground-based OpenAir™ plasma pre-treatment has been researched. Oxygen plasma asher testing and complementary surface analysis techniques have been used to assess the surface composition, bounding states and atomic oxygen resistance of the treated materials. It was shown that the application of this approach may essentially simplify the technological development to reduce or prevent contamination caused by silicone-coated space materials and structures.
Properties and Improved Space Survivability of POSS (Polyhedral Oligomeric Silsesquioxane) Polyimides
Authors: Tomczak Sandra J. , Marchant Darrell , Svejda Steve , Minton Timothy K. , Brunsvold Amy L. , Gouzman Irina , Grossman Eitan , Schatz George C. , Troya Diego , Sun LiPeng , Gonzalez Rene I.
Published: April 2011

Kapton polyimide (PI) is widely used on the exterior of spacecraft as a thermal insulator. Atomic oxygen (AO) in lower earth orbit (LEO) causes severe degradation in Kapton resulting in reduced spacecraft lifetimes. One solution is to coat the polymer surface with SiO2 since this coating is known to impart remarkable oxidation resistance. Imperfections in the SiO2 application process and micrometeoroid / debris impact in orbit damage the SiO2 coating, leading to erosion of Kapton.

A self passivating, self healing silica layer protecting underlying Kapton upon exposure to AO may result from the nanodispersion of silicon and oxygen within the polymer matrix. Polyhedral oligomeric silsesquioxane (POSS) is composed of an inorganic cage structure with a 2:3 Si:O ratio surrounded by tailorable organic groups and is a possible delivery system for nanodispersed silica. A POSS dianiline was copolymerized with pyromellitic dianhydride and 4, 4′-oxydianiline resulting in POSS Kapton Polyimide. The glass transition temperature (Tg) of 5 to 25 weight % POSS Polyimide was determined to be slightly lower, 5 – 10 %, than that of unmodified polyimides (414 °C). Furthermore the room temperature modulus of polyimide is unaffected by POSS, and the modulus at temperatures greater than the Tg of the polyimide is doubled by the incorporation of 20 wt % POSS.

To simulate LEO conditions, POSS PI films underwent exposure to a hyperthermal O-atom beam. Surface analysis of exposed and unexposed films conducted with X-ray photoelectron spectroscopy, atomic force microscopy, and surface profilometry support the formation of a SiO2 self healing passivation layer upon AO exposure. This is exemplified by erosion rates of 10 and 20 weight % POSS PI samples which were 3.7 and 0.98 percent, respectively, of the erosion rate for Kapton H at a fluence of 8.5 × 1020 O atoms cm-2. This data corresponds to an erosion yield for 10 wt % POSS PI of 4.8 % of Kapton H. In a separate exposure, at a fluence of 7.33 × 1020 O atoms cm-2, 25 wt % POSS Polyimide showed the erosion yield of about 1.1 % of that of Kapton H. Also, recently at a lower fluence of 2.03 × 1020 O atoms cm-2, in going from 20 to 25 wt % POSS PI the erosion was decreased by a factor of 2 with an erosion yield too minor to be measured for 25 wt % POSS PI.
Increased Ordering in the Amorphous SiOx due to Hyperthermal Atomic Oxygen.
Authors: Kisa Maja , Stratton William G. , Minton Timothy K. , Benthem Klaus van , Pennycook Steve J. , Voyles Paul M. , Chen Xidong , Li Long , Yang Judith C.
Published: April 2011

We had studied the effects of hyperthermal (5.1eV) atomic oxygen (AO) on the structural characteristics of the silica layer and Si/SiOx interface formed by the oxidation of Si-single crystal by a variety of microcharacterization techniques. A laser detonation source was used to produce atomic oxygen with 5.1eV kinetic energy. High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED) demonstrated that the silica layer formed on Si(100) by atomic oxygen is thicker, more homogeneous, and less amorphous, compared to the oxide layer created by molecular oxygen (MO). High spatial resolution Electron Energy Loss Spectroscopy (EELS) study confirmed that the Si/SiOx interface created by atomic oxygen is abrupt containing no suboxides as opposed to the broad interface with transitional states formed by molecular oxygen. SAED technique was used to observe sharper diffraction rings present in the diffraction pattern of Si(100) oxidized by reactive atomic oxygen as opposed to the diffused haloes present in the diffraction pattern of Si(100) oxidized by molecular oxygen. Radial Distribution Function (RDF) analyses were performed on the SAED patterns of Si(100) oxidized in atomic and molecular oxygen, indicating that a more ordered oxide is formed by atomic oxygen. Initial Fluctuation Electron Microscopy (FEM) results confirmed an increased medium range ordering in SiOx formed by atomic oxygen when compared to the non-regular arrangement present in the amorphous oxide formed by the oxidation of Si(100) in molecular oxygen.
An Investigation of the Chemical Changes of Artists' Acrylic Paint Films When Exposed to Water
Authors: Ploeger R. , Murray A. , Hesp S. , Scalarone D.
Published: April 2011

This paper addresses some of the conservation concerns of artists' acrylic paints by investigating the chemical changes of the paint films caused during a one-hour exposure to water experiments and the rate at which some of the changes occur. Three different acrylic paint films were investigated. Real-time capillary rise, conductivity measurements and thermo-mechanical analysis (TMA) gave an indication of the rate at which these changes occurred. Much of the measurable leaching occurred within the first 20 minutes of the paint film being exposed to water, while the most rapid leaching occurred within the first five minutes, before approaching an equilibrium state. All physical and visual changes in colour, gloss, dimension, mass and surface morphology (using atomic force microscopy, AFM) were monitored. A decrease in size and mass indicated that material had been permanently removed from the paint films. Gloss and colour measurements, as well as AFM images, also showed evidence of changes caused by the exposure to water.
Using ICP-MS to Detect Inorganic Elements in Organic Materials: A New Tool to Identify Mordants or Dyes on Ancient Textiles
Authors: Dussubieux Laure , Ballard Mary W.
Published: April 2011

The feasibility of determining metallic elements used as mordants or dyes with inorganic constituents was tested using inductively coupled plasma – mass spectrometry (ICP-MS). For this purpose, modern, historic and archaeological samples were investigated. Mordants containing copper, iron, tin, aluminium or uranium were successfully identified as well as an organic dye with a substitutional bromine.
Estimation of Elastic Constants of Restoration Mortars, Used on Historic Masonries Restoration Interventions, VIA Ultrasonic Technique and Correlation to their Mechanical and Microstructure Parameters
Authors: Moropoulou Antonia , Bakolas Asterios , Aggelakopoulou Eleni , Odatzidou Anastasia , Teas Christos , Papageorgiou Dimitris
Published: April 2011

Eight syntheses of mortars used for restoration interventions in historic masonry were produced using the traditional materials of aerial lime and artificial pozzolanic additives. The mortars were aged over a 15-month period and then tested for properties related to chemical and mechanical stabilization using the following four analytical techniques: ultrasonic velocity propagation and the mortars' dynamic modulus of elasticity (Ed), mercury intrusion porosimetry for evaluation of microstructural characteristics (percentage open porosity, bulk density, average pore radius, total cumulative volume, and specific surface area), water capillary rise tests for the determination of total cumulative volume accessible to water and capillary rise coefficients of the mortars, and conventional mechanical tests for the determination of the mortars' flexural and compressive strength. Performance is correlated to the mortars' chemical composition, microstructural characteristics (as measure by average pore radius) and mechanical characteristics as measured by dynamic modulus of elasticity (Ed) and flexural and compressive strength (Fc).
Understanding Bronze Age Faience in Britain and Ireland
Authors: Sheridan Alison , Eremin Katherine , Shortland Andrew
Published: April 2011

Around 350 Bronze Age faience beads and pendants are known from Britain and Ireland, mostly from burials of cremated human bone. Their relationship with Near Eastern and Mediterranean faience has long been debated. A National Museums of Scotland (NMS) led international research project is investigating their origin, composition, manufacture and use (inter alia) for aCorpusof faience from Britain, Ireland and adjacent parts of mainland Europe. Non-destructive controlled-pressure scanning electron microscopy with energy dispersive microanalysis (CP-SEM-EDS), X-ray fluorescence (XRF) and binocular microscopy provide compositional and textural information without sampling or coating. Wavelength-dispersive electron microprobe (EMP) analysis of rare polished samples provides additional and more accurate compositional information. The results demonstrate that direct derivation from Egyptian or Mediterranean faience traditions can be ruled out. The beads and pendants were manufactured on a small-scale basis, using mostly a mixed alkali paste and glaze from plant ash sources (including seaweed) and a copper-based glaze colorant probably derived from bronze. Tin (or its oxide) seems to have been deliberately added. Various forming and glazing techniques were used. We have demonstrated, for the first time, that some beads were worn during cremation; and we have further investigated the effects of cremation on faience by experimentally cremating a pig wearing a newly-made faience necklace.
Technical Study of Pigments and Paintings in Archaeological Ceramics from Northwestern Argentine Region: An Archaeometric Approach and Implications for Their Conservation Through SEM-EDS.
Authors: De La Fuente Guillermo A.
Published: April 2011

The ancient technology involved in the application of pigments and paintings used by potters to decorate ceramic vessels is one of the most interesting aspects of ceramic technology in the past. Potters have used in the past several sources (e.g. inorganic and organic) to decorate the vessels in order to achieve the colours desired and fix them in the vessels throughout the firing process. In this paper, we present the results of a technological and chemical characterisation of pigments and paintings through the application of Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) to ceramics from the Middle Period (ca. 650 AD – 900 AD) at Northwestern Argentine region.
Functionalization of Nanomaterials utilizing Pulse Thermal Processing
Authors: Kadolkar Puja B. , Ott Ronald D. , Blue Craig A. , Sabau Adrian S.
Published: April 2011

Pulse Thermal Processing (PTP) using a High Density Infrared (HDI) Plasma Arc Lamp has been investigated as an enabling manufacturing tool for processing nanomaterials and thin-films. HDI is a single source lamp that offers unique capabilities of processing broad areas with power densities approaching those of a laser. The extremely high radiant energies delivered by the plasma arc lamp provides heating rates approaching 600, 000°C/s through a single pulse on a millisecond time frame, thus allowing controlled diffusion on nano-meter scale. The ability to design the functionality of nanomaterials offers tremendous potential to exploit this technology for a wide range of applications based on nanotechnology. This present article discusses application of PTP using high-density plasma arc lamp to perform; a) phase transformation in FePt nanoparticle system for magnetic media applications, and b) crystallization of amorphous Si (a-Si) for photovoltaic and thin-film transistor (TFT) applications.
Synthesis and Characterization of Magnetic Iron Oxide Nanoparticles
Authors: Wang Lingyan , Luo Jin , Maye Mathew M. , Fan Quan , Rendeng Qiang , Wang Jian Q. , Engelhard Mark H. , Wang Chongmin , Lin Yuehe , Altman Eric I. , Zhong Chuan-Jian
Published: April 2011

This paper describes the results of an investigation of modified synthetic protocols to produce monodispersed magnetic ferrite nanoparticles, γ-Fe2O3 and Fe3O4, and their magnetic properties. The synthesis involved thermal decomposition of organometallic precursors followed by oxidation or reduction. In the synthesis of γ-Fe2O3, iron pentacarbonyl was used as the precursor and trimethylamine oxide as the oxidant. In the synthesis of Fe3O4, iron (III) acetylacetonate was reduced by 1, 2-hexadecanediol. The particle sizes ranged from 5–15 nm with high monodispersity. Results from TEM, XPS, and SQUID characterizations of these iron oxide nanoparticles are discussed.
Direct Measurements of Fracture Toughness and Crack Growth in Polysilicon MEMS
Authors: Chasiotis I. , Cho S.W. , Jonnalagadda K.
Published: April 2011

Direct measurements of Mode-I critical stress intensity factor and crack tip displacements were conducted in the vicinity of atomically sharp edge cracks in polycrystalline silicon MEMS using our in situ Atomic Force Microscopy (AFM)/Digital Image Correlation (DIC) method. The average Mode-I critical stress intensity factor for various fabrication runs was 1.00 ± 0.1 MPa√m. The experimental crack tip displacement fields were in very good agreement with linear elastic fracture mechanics solutions. By means of an AFM, direct experimental evidence of incremental crack growth in polycrystalline silicon was obtained for the first time via spatially resolved crack growth measurements. The incremental crack growth in brittle polysilicon is attributed to its locally anisotropic polycrystalline structure which also results in different local and macroscopic (apparent) stress intensity factors.
Temperature Dependence of Stress Distribution in Depth for Cu Thin Films
Authors: Himuro Tokuji , Takayama Shinji
Published: April 2011

The stress distribution of (111) textured Cu films with depth was measured by using a GIXS method. We derived the equation to correct a scattering diffraction angle with depth, measured in the GIXS Seemann-Bohlin geometry, to obtain the actual scattering angle. It was revealed after the correction of the measured scattering angles that the internal stresses of (111) grains, on the whole, tend to increase almost linearly with increasing film depth from the free surface toward the substrate. It was suggested that these results were opposite to the results of the elastic calculation reported, and hence that a large stress relaxation took place during and/or after deposition and annealing. After annealing at various temperatures, these stress distribution profiles are almost unchanged, and are simply shifted uniformly in magnitude.
Microstructure Evolution Across Interfaces of Heterogeneous Metal Systems Under Ultrasonic Impact
Authors: Li Youhong , Ashkenazy Yinon , Averback Robert S.
Published: April 2011

Large-scale Molecular Dynamics (MD) studies on heterogeneous, model metal systems subjected to intense shock loading by a flyer plate were carried out. Of interest here is the effect of structural defects on interfacial strength under these extreme conditions. The metal target and flyer were essentially single crystals of Cu, but an interface layer was created by varying the mass of the Cu atoms in part of the sample. Interfacial defects in the form of vacancies, and at different concentrations, were introduced into the interfacial region. In addition to microstructural evolution of damage in this system, the shock induced temperature and pressure changes were also analyzed.
Confinement Effects in Nanoscale Anodic Alumina Structures on Silicon
Authors: Griffin Patrick J. , Carpick Robert W. , Stone Donald S.
Published: April 2011

Anodic aluminum oxide (AAO) has long been considered a viable material for templated growth of nanomaterials for electronic, magnetic and optical applications due to the ability to form self-organized, high aspect-ratio nanochannels. More recently these porous materials have been incorporated with silicon to create a template for nanostructured materials on a semiconducting substrate. However, there has been no investigation into how pore growth is affected by confining the pre-anodized aluminum dimensions to the nanometer scale. We have used electron beam lithography to pattern 200 nm thick aluminum structures on Si with lateral features ranging from 100 nm to several microns in size. Structures consisting of 1 – 10 individual pores 10 – 15 nm in diameter are routinely fabricated. Confinement effects in the narrowest features assist in pore ordering in the porous structures without the use of pre-patterning or a two step anodization.
Stress Stability of Poly-SiGe and Various Oxide Films in Humid Environments
Authors: Low Carrie W. , Bircumshaw Brian L. , Dorofeeva Tatiana , Solomon Gelila , King Tsu-Jae , Howe Roger T.
Published: April 2011

This paper presents the stress stability of thin films for MEMS structural and sacrificial layers. The average residual stresses of the thin films were monitored via wafer curvature measurement over a long period of time. Poly-Si, poly-SiGe, poly-Ge and thermally growth SiO2films are found to be stable in humid environments. Moisture makes LPCVD and TEOS-based PECVD SiO2films more compressive over time. Multi-layer thin film stress is modeled with the same methodology used to derive the Stoney Equation [1].
Stability and Structural Transition of Gold Nanowires under Their Own Surface Stresses
Authors: Gall Ken , Haftel Michael , Diao Jiankuai , Dunn Martin L. , Bernstein Noam , Mehl Michael J.
Published: April 2011

First-principle, tight binding, and semi-empirical embedded atom calculations are used to investigate a tetragonal phase transformation in gold nanowires. As wire diameter is decreased, tight binding and modified embedded atom simulations predict a surface-stress-induced phase transformation from a face-centered-cubic (fcc) <100> nanowire into a body-centered-tetragonal (bct) nanowire. In bulk gold, all theoretical approaches predict a local energy minimum at the bct phase, but tight binding and first principle calculations predict elastic instability of the bulk bct phase. The predicted existence of the stable bct phase in the nanowires is thus attributed to constraint from surface stresses. The results demonstrate that surface stresses are theoretically capable of inducing phase transformation and subsequent phase stability in nanometer scale metallic wires under appropriate conditions.
In situ TEM Observations of Grain Growth in Nanograined Thin Films
Authors: Hattar K. , Gregg J. , Han J. , Saif T. , Robertson I. M.
Published: April 2011

In situ transmission electron microscopy analysis is used to study the stability of nanograined and ultra-fine grained thin films at elevated temperatures. In the free-standing Au and Cu films, grain growth was dependent on annealing temperature and time with growth observed in both materials at temperatures greater than 373K. Both materials exhibited abnormal grain growth although it was more prevalent in Au than in Cu, which may be a consequence of pinning of the Cu grain boundaries by impurities. The formation and destruction of twins was observed to play a critical role in the grain growth, with the twins retarding the growth in gold, but not in Cu. In constrained Au films no grain growth was observed on annealing at temperatures below 636 K. At 636 K, the eutectic temperature, the microstructure transformed to the eutectic structure with the first stage being the annihilation of the grain structure.
Morphology and Microstructure Evolution of Multilayer Au/Cr/Si Thin Films Subject to Annealing
Authors: Miller David , Herrmann Cari , Maier Hans , George Steve , Stoldt Conrad , Gall Ken
Published: April 2011

Au/Cr/Si microcantilevers were studied in their as-deposited condition and annealed state, with emphasis on a thermal treatment of 225 °C for 24 hours. Change in beam curvature was monitored during isothermal hold as a function of time. Secondary grain growth was observed in the gold, which contained non-uniformly distributed twins and dislocation defects. Diffusional transport of the chromium layer was observed during annealing. Nodules arranged in the “rolling hill” topography were observed at the free surface, both before and after annealing. Nanometer thick coatings of alumina grown by atomic layer deposition improved the uniformity of both microstructure evolution and curvature evolution during high-temperature annealing.
Thickness-dependent Structural Relaxation of Plasma-Enhanced Chemical Vapor Deposited Silicon Oxide Films during Thermal Processing
Authors: Cao Zhiqiang , Zhang Xin
Published: April 2011

This paper presents a microstructure-based mechanism which elucidates seams as a source of density change and voids as a source of plastic deformation, accompanied by a viscous flow. This theory was then applied to explain a series of experimental results that are related to thermal cycling of amorphous dielectric films, such as plasma-enhanced physical vapor deposited (PECVD) silicon oxide (SiOx) films, including stress hysteresis generation and reduction and coefficient of thermal-expansion changes. In particular, the thickness effect was examined; PECVD SiOx films with a thickness varying from 1 to 40 m were studied, as certain demanding applications in Microelectromechanical Systems (MEMS) require such thick films serving as heat/electrical insulation layers.
Development of Magnetostrictive Fe-Ga and Fe-Pd Thin Films
Authors: Okazaki Teiko , Watanabe Satoru , Okanisi Norimasa , Ono Toshiro , Furuya Yasubumi , Michigami Munemi , Sakisaka Yasuo , Takeuchi Ichiro , Wuttig Manfred
Published: April 2011

The giant magnetostrictive films exhibit promising device applications for micro-machines and sensor systems due to high response velocity and huge stress created by the magnetostriction. We developed magnetostrictive bimorph-type Fe70Pd30 or Fe83Ga17 (positive magnetostriction)/Al/Ni(negative magnetostriction) thin films by magnetron sputtering. Magnetostriction of these films measured by a bending cantilever beam method has reached 250–300 ppm in the small magnetic field of 1.0 kOe and exhibits little hysteresis. Moreover, the magnetostrictive characteristics do not change under low alternating magnetic field. The magnetoelastic coefficient of these films is 25∼30 MPa, which is comparable to the coefficient of the PbTiO3-PbZrO3 system. These metallic sensor/actuator materials are useful for applications in magnetostrictive 2D- scanners and remote-interrogated tire sensors.
Thermomechanics of the Shape Memory Effect in Polymers
Authors: Liu Yiping , Gall Ken , Dunn Martin L , Greenberg Alan R
Published: April 2011

Shape memory polymers (SMPs) have the capacity to store and recover relatively large strains when subjected to a unique thermomechanical cycle. In this study, the thermomechanics of strain storage and strain/stress recovery are investigated in a shape memory polymer deformed under uniaxial tension and compression. During heated recovery, three cases of constraint are examined: unconstrained (free) strain recovery, stress recovery under pre-strain constraint, and stress recovery under fixed-strain constraint. Based on the experimental results, a one-dimensional SMP constitutive model is developed, which is motivated by the shape memory mechanism of the polymer network. The foundation of the model is that the entropy change is gradually stored during cooling and released during reheating as free recovery strain or constrained recovery stress. When fit to free strain recovery data, the model can predict the trends of the stress evolution during shape fixation and constrained strain/stress recovery under various thermomechanical conditions.
Enhanced Raman signal of CH3 on carbon nanotubes
Authors: Bassil A. , Puech P. , Landa G. , Bacsa W. , Hubel H. , Dunstan D. J. , Barrau S. , Demont Ph. , Lacabanne C. , Perez E. , Flahaut E. , Bacsa R. , Peigney A. , Laurent Ch.
Published: April 2011

We find that functionalized SWCNT and DWCNT's (mainly double wall carbon nanotubes) in composites, DWCNTs under hydrostatic pressure and blue illuminated DWCNTs in methanol show the same up shift of the Raman G band and the appearance of a new band at 1455cm−1. This is attributed to the interaction of the CH3 group of the amphiphilic molecule in composites or the CH3 group of alcohol with the outer tube of DWCNT's and indicates that laser heating of DWCNT's in methanol can induce the chemical adsorption of CH3 onto the CNT (carbon nanotube) surface.
Growth, Nitrogen Doping and Characterization of Isolated Single-Wall Carbon Nanotubes using Liquid Precursors
Authors: Keskar Gayatri , Rao Rahul , Luo Jian , Hudson Joan , Rao Apparao M.
Published: April 2011

Isolated single wall carbon nanotubes (SWNTs) were prepared on bare quartz and SiO2/ Si substrates using chemical vapor deposition (CVD) in which a liquid precursor, such as xylene, was used as the carbon source. The coverage of isolated SWNTs on the substrates was controlled by adjusting the concentration of iron (III) nitrate nonahydrate/2-propanol solution which provided the Fe seed catalyst particles. Micro-Raman spectra were obtained using the 514.5 nm excitation which showed the typical tangential band around 1590 cm−1 for semiconducting nanotubes. The radial breathing mode (RBM) frequencies ranged between 150 to 240 cm−1 and the estimated tube diameters are in good agreement with those obtained from atomic force microscope (AFM) images. In our synthesis approach controlled doping of isolated SWNTs with nitrogen was achieved by mixing appropriate amount of acetonitrile with xylene. As the nitrogen concentration in the feed was increased from 0 – 33 at. %, the RBM intensity decreased dramatically while the intensity of the D-band increased gradually relative to that of the G-band. Interestingly, the D' band was observed for the first time in the Raman spectrum of carbon nanotubes when the nitrogen concentration reached ∼2–3 at. %.
Arc-Discharge Evaporation of Silver-Plated Graphite Rods
Authors: Vaziri M.
Published: April 2011

In this work, several silver-plated graphite rods have been evaporated using the dc-arc discharge technique in the presence of helium quenching gas. The evaporated materials deposited on the cathode and the chamber walls were characterized. It was found that the inner core of the deposited materials contains no encapsulated silver but unusually long bundles of carbon nanotubes. In addition, the soot removed from the walls presents evidence for encapsulated nanocrystalline silver as well as low-mass fullerene cages.
NMR Investigation of n-Alkylamine Self-Organization Along the Sidewalls of Single-Wall Carbon Nanotubes (SWNTs)
Authors: Ju Sang-Yong , Utz Marcel , Papadimitrakopoulos Fotios
Published: April 2011

Single wall carbon nanotubes (SWNTs) have drawn considerable attention from the scientific community based on their potentially unique 1-D electronic and optical properties as well as mechanical properties. These characteristics result from the one dimensional quantum wire structure of CNTs, which have the spike-like van Hove singularities (vHs) in the electronic density of states. The detailed shape of the density of states function depends sensitively on CNT type semiconducting (sem-) versus metallic (met-)), diameter and chirality. Using the preferential affinity of amines towards sem -SWNTs, our group has been able to attain bulk separation by type based on a differential solubility of SWNTs according to the amine organization interaction on the nanotube surface. It has been argued that stable dispersions of sem -SWNTs with surfactant-amines originate from the organization of the aliphatic chain along the nanotube sidewalls, along with a small amount of zwitterions. The separation of sem-enriched SWNTs assisted by octadecylamine (ODA) had been depicted in the form of either small amount of zwitterionic interaction between carboxylic acid groups of acid-purified SWNTs or the physisorption on the SWNTs sidewall, leaving met -SWNTs in the precipitate.
Electrical Conductivity and Electromagnetic Interference Shielding of Multi-walled Carbon Nanotube Filled Polymer Composites
Authors: Yang Yonglai , Gupta Mool C. , Dudley Kenneth L. , Lawrence Roland W.
Published: April 2011

Multi-walled carbon nanotube (MWNT) filled polystyrene (PS) composites were synthesized for electromagnetic interference (EMI) shielding applications. SEM images of composites showed the formation of the conducting networks through MWNTs within the PS matrix. The measured DC conductivity of composites increased with increasing MWNT loading, showing a typical percolation behavior. EMI shielding characteristics of MWNT-PS composites were investigated in the frequency range of 8.2–12.4 GHz (X-band). It was observed that the shielding effectiveness (SE) of such composite increased with the increase of MWNT loading. The SE of the composite containing 7 wt% MWNTs could reach more than 26 dB in the measured frequency region.
First-Principles Study of Epitaxial Growth of Zinc-Blende CrAs on GaAs Substrates
Authors: Mukose Kiichiro , Kusakabe Koichi , Suzuki Naoshi
Published: April 2011

We study the epitaxial growth mechanisms of the zinc-blende CrAs on the GaAs substrates theoretically, from the first principles using the pseudopotential method. We assume some model structures containing various numbers of Cr adatoms or CrAs films on the GaAs (001) substrates, and compare the structural stabilities of them. We found that Cr adatoms may make some interstitial defects in the GaAs substrate in low coverage, but they can create a complete Cr layer in high coverage.
From Atomistic to Continuum Descriptions of Morphological Evolution
Authors: Haselwandter Christoph A. , Vvedensky Dimitri D.
Published: April 2011

Lattice Langevin equations are derived from the rules of lattice growth models. These provide an exact mathematical description that is suitable for direct analysis, such as the passage to the continuum limit, as well as a computational alternative to kinetic Monte Carlo simulations. This approach is applied to ballistic deposition and a model for conditional deposition, both of which yield the Kardar–Parisi– Zhang equation in the continuum limit, and a model of strain relaxation during heteroepitaxy.
“Enhanced Layer Coverage of Thin Films by Oblique Angle Deposition”
Authors: Karabacak Tansel , Wang Gwo-Ching , Lu Toh-Ming
Published: April 2011

The characteristics of nucleation and island growth in oblique angle deposition with substrate rotation have recently attracted interest due to the formation of novel 3D nanostructures by a physical self-assembly process. In this study, we present the results of a solid-on-solid growth simulation by a kinetic Monte Carlo algorithm that explores the layer coverage evolution of thin films during oblique angle deposition. The simulations accounted for oblique incidence flux, shadowing effect, surface diffusion, and substrate rotation. The layer coverage, the ratio of average island volume to average island size, and root-mean-square (RMS) roughness values are reported for the initial stages of island growth from submonolayer thicknesses up to a few monolayers. RMS roughness was also investigated for later stages of the growth. Our results show that, for small deposition angles and with limited or no surface diffusion included, the average growth rate of islands is faster in lateral directions that results in enhanced layer coverages and smoother films. This is due to that the sides of the islands can be exposed to the incident flux more effectively at small deposition angles. On the other hand, normal incidence and high oblique angle depositions give poorer layer coverages and much rougher films due to the slower growth rates in lateral directions.
A New Type of Partnership for Science Outreach: Princeton Center for Complex Materials, Strange Matter and the Liberty Science Center
Authors: Steinberg Daniel
Published: April 2011

All National Science Foundation funded MRSEC centers have education, outreach and community service as one of their major objectives. The Princeton Center for Complex Materials (PCCM) takes this commitment very seriously. PCCM runs a full slate of education activities including a host of Pre-college science and engineering programs and a research experience for undergraduates and teachers program each summer. Our outreach programs are designed to increase awareness, appreciation and knowledge of materials science.

Liberty Science Center (LSC) in Jersey City, New Jersey and the Strange Matter traveling exhibit allowed PCCM to expand its outreach program to include tens of thousands of family audience members. LSC gets 1000's of visitors each weekend, and has expertise in communicating with this audience. Princeton University scientists have expertise in materials science. This partnership required coordination between the LSC staff and the PCCM outreach director in facilitating the training and presentations by faculty and other scientists from Princeton. Together we developed a program that sent over 30 scientists from Princeton University to the liberty science center to offer their enthusiasm for material science to the public. Scientists can reach a much larger audience at a science center than at their home institutions. This can be repeated anywhere in the country where there are science centers is and university research centers willing to work together.
Exploring Materials Science with LEGO® Brick Models
Authors: Campbell Dean J.
Published: April 2011

Various physical and chemical principles related to materials science and technology can be demonstrated with LEGO® models. Three-dimensional models are excellent tools for grasping structure-function relationships. Additionally, many people are familiar with LEGO® bricks, and most models can be built with a level of mechanical sophistication that does not intimidate or frustrate the user. LEGO® bricks typically have many connection sites, allowing tremendous flexibility in the structures that can be built. The bricks can be used to model both the structures of materials and the techniques used to study them. Many models can be built with varying degrees of sophistication, even incorporating electronics, enabling the user to focus on relatively simple concepts or more subtle details. The variety of models available also enables LEGO® bricks to fit into a variety of user budgets. This paper features models of the structures of materials, including unit cells, discrete molecules, and polymers. It also features models of analytical tools used to study materials, including models of a scanning probe microscope and a photometer. Details and building instructions of these and other models are featured in the book “Exploring the Nanoworld with LEGO® Bricks”. This book may be downloaded from the Internet at: http://mrsec.wisc.edu/edetc/LEGO/index.html.
Accommodating Different Learning Styles Using e.g., “Flash Movies” in an Introductory Course on Materials Science.
Authors: Harrison I. R. , Ray P. C. , Fleck M. , Locklin R. H. , Weisner A. , Howell P. R.
Published: April 2011

In addition to a hard-copy textbook, Power-Point presentations and videos, the authors have developed a series of Flash modules and on-line quizzing tools for use in teaching and assessing the fundamentals of Materials Science and Engineering. The original thrust was aimed at non-science majors at university, but the modules are also designed for ease of use in high school curricula. In the current paper, we present our philosophy for the presentation of materials' related subject material, using different learning objects, by describing one particular module: on electronic materials.
Experimental Study on the Mechanism of Ethanol/Bentonite Slurry Grouting
Authors: Ishii Takashi , Iwasa Kengo , Shiraishi Tomonari , Saito Akira , Nakashima Hitoshi , Asada Motoyuki , Ueda Hiroyoshi , Sakabe Yasushi
Published: April 2011

To ensure safety and efficiency of construction and operation of repositories, rock fractures need to be grouted where they intersect the facility. Cement-based grouting materials that have been used extensively in the past may, however, react with the groundwater and produce hyperalkaline leachate. A possible solution for this issue is use of alternative material.

Ethanol/Bentonite Slurry Grouting is another approach to minimize the long-term permeability of rock fractures. The slurry has high fluidity for the case of the ethanol concentration in the liquid phase being 60%. The viscosity of the slurry with bentonite content of 0.4 Mg/m3 was measured for conditions of the shear rate ranging from 0.1 to 1000 1/s. The viscosity of the slurry changed dramatically between the ethanol concentrations of 60 to 40 %, behaving as a non-Newtonian fluid. In order to investigate when the ethanol content of the slurry becomes low enough to achieve sufficient viscosity in rock fractures, an Ethanol Diffusion Test with experimental openings was carried out in the laboratory. Extrapolation of the measured minimum time for the filled slurry to reach the desirable low concentration of ethanol lead to the estimated minimum time ranging from 0.1 hours to 0.7 hours for a 0.2 mm aperture. These facts suggest that the injected slurry flows through the openings of fractures during the early period of injection and, later, as its ethanol content decreases, slurry's viscosity increases sufficiently so that the openings can be blocked.